TL neuro

June 22, 2018

An oxycodone vaccine prevents the acquisition of self-administration

Filed under: Opiates, Vaccines — mtaffe @ 2:59 pm

A paper from the laboratory has recently been accepted for publication .

Nguyen*, J.D., Hwang*, C.S., Grant, Y., Janda, K.D.. and Taffe, M.A. Prophylactic vaccination protects against the development of oxycodone self-administration.  Neuropharmacology, 2018, 138:292-303. [ Publisher Link ][ Free Author Share ]

This paper reflects joint effort with members of the Janda laboratory in our ongoing collaboration [ related posts ] to evaluate their anti-drug vaccines for efficacy in rat models of drug exposure and abuse. In this study we focused on a vaccine that induced antibodies that bind to oxycodone and evaluated the efficacy of this active vaccine (Oxy-TT) versus the carrier protein tetanus toxoid (TT). Our primary goal was to examine the intravenous self-administration of oxycodone in the rats.

This reorganization of Figure 2 from the paper depicts one of the key findings. The right panel shows the average number of infusions of oxycodone (0.06 mg/kg/infusion) obtained by subgroups of the Oxy-TT and TT rats. This median split analysis divides the Upper from Lower halves of the distribution based on average oxycodone responding across the 18 session acquisition interval. The distribution for the Oxy-TT group was more bimodal compared with the TT control group, indicating that some Oxy-TT rats took very little oxycodone across the acquisition period and some self-administered more. We defined successful acquisition as an average of 7 or more infusions obtained across two sequential days and the left panel reflects the proportion of the entire distributions of TT versus Oxy-TT that met this standard. Combined, we can infer that about 40% of the Oxy-TT animals essentially failed to acquire stable self-administration behavioral whereas all of the TT group did under these conditions. While it may seem disappointing to some eyes that the vaccine “worked” to prevent the establishment of stable self-administration in only 40% of the animals, this needs to be viewed in the context of human substance abuse. Only minorities of the individuals who try a given drug will go on to develop a habitual use pattern. This can be observed (cross-sectionally) in the Monitoring the Future data [vol 1 adolescents; vol 2 adults], in Schramm-Sapyta et al 2009 and in Anthony et al, 1994. The best way to reduce harm from repetitive use problems with drugs is to prevent it from progressing to this stage in the first place. Our study shows that the Oxy-TT vaccine is potentially capable of protecting a substantial subset of those individuals who sample a drug enough to become habitual users.

These panels from Figure 5 of the paper show that there was basic biological efficacy of the vaccine. These data show the plasma (left panel) and brain (right panel) amounts of oxycodone in the two vaccine groups after administration of 1.0 or 2.0 mg/kg subcutaneously. This shows that considerably more oxycodone is in the plasma of the Oxy-TT groups (as is expected since the antibodies should retain drug in the bloodstream and not let it get into other tissues. Lesser amounts of oxycodone were in the brains of the Oxy-TT group as well which is again consistent with the anticipated effects of successful anti-drug vaccination.

The second major behavioral finding is a bit more subtle. As you can see from the first figure, above, the Oxy-TT rats that did acquire self-administration responded for more drug than did the TT control animals. This is consistent with the second figure, i.e., that less of each infusion of drug was reaching the brain. Thus, assuming the rats on average seek the same approximate amount of drug in their brain, the vaccine resulted in an increase in self-administration behavior. In order to probe the extent to which the rats prefer to self-administer oxycodone we increased the workload. In training the rats only had to make one lever response for each infusion of drug, known as a Fixed Ratio 1 (FR1) contingency. But the Progressive Ratio procedure makes each successive infusion within the daily session cost more. When we did that, the Oxy-TT animals decreased their intake to a greater extent than did the TT rats. This figure is from a second cohort of rat groups that were trained to self-administer a

higher per-infusion dose (0.15 mg/kg/inf) of oxycodone. Under these conditions the Lower half of the Oxy-TT group self-administered about the same amount of drug as the entire TT group and the Upper half self-administered more. The figure depicts mean intake, post-acquisition, in four different workload conditions, starting and ending with the FR1 training condition. The two middle bars depict the oxycodone intake under two PR schedules which differ in steepness of the incrementing workload. There was a change for the TT group only in the hardest PR condition but this did not reach statistical significance. In contrast the overall number of infusions in a session that were obtained by the Oxy-TT animals (this is for the entire group) were reduced when it took more responses to obtain successive infusions. This shows that despite self-administering slightly more oxycodone when it is easy to get (FR1), the Oxy-TT animals are more likely to reduce their intake when the conditions are made slightly more difficult. Making drugs more difficult to obtain is, of course, one of the population level strategies we use to combat drug addiction. This is reflected in taxes and the regulation of sales of alcohol and tobacco that have been proven to reduce problematic use of these legal substances. Parents routinely use different strategies to make it more difficult for their teenagers to access drugs of all types. Many therapeutic interventions for drug abusers involve lifestyle changes that make getting access to drug more laborious. Thus, a strategy that makes an individual more liable to reduce their drug use when the costs increase has the potential for success in reducing drug use harms.

This last finding also has important implications for the design of human clinical trials that attempt to test the efficacy of anti-drug vaccines. The default approach has been to use measures of drug use as the measure of “success” of the trial. These data suggest that vaccinated people could use the same or even slightly more drug and still be getting a protective effect. That is, they might become more susceptible to other interventions which, for example, raise the cost or effort of getting drug.

__

*authors contributed equally

Funding for this work provided by USPHS Grants R01 DA035281, R01 DA024705, UH3 DA041146 (K.D.J.) and F32 AI126628 (C.S.W.).

Advertisements

October 16, 2017

High ambient temperature facilitates MDMA self-administration

Filed under: IVSA, MDMA, Thermoregulation — mtaffe @ 1:02 pm

The following has recently been accepted for publication:

Aarde, S.M., Huang, P-K  and Taffe, M.A. High Ambient Temperature Facilitates The Acquisition Of 3,4-Methylenedioxymethamphetamine (MDMA) Self-Administration. Pharmacol Biochem Behav, 2017, in press.  [ Publisher Site ][ PubMed ]

This study was motivated by a finding from Cornish and colleagues in 2003 where they showed that rats trained to self-administer MDMA at 21 °C ambient temperature will significantly increase their drug intake when placed in a 30 °C ambient temperature. This finding was of interest to our lab because of our longstanding interest in the role of the body temperature response to MDMA. In brief, the effect of a given dose of MDMA at ~21-24 °C is generally to lower a rat’s body temperature whereas the same dose given at ~27-30 °C elevates body temperature. The typical laboratory ambient temperature of about 21-24 °C is actually somewhat cold for a rat since their point of thermoneutrality is up around 30 °C.  This led us to think that perhaps one of the reasons why MDMA is a poor reinforcer in the intravenous self-administration (IVSA) paradigm is because it lowers body temperature. If this effect is aversive to the rat, this may oppose the rewarding properties of the drug. Consequently, the Cornish finding may have illustrated increased IVSA due to a blunted hypothermia (but that study didn’t measure it). This rationale formed the basis for an entire Aim of a grant proposal which was submitted in original form in 2007 and eventually funded in 2011 (R01 DA024105-01A2).

In this figure from the paper we present the number of MDMA infusions (1.0 mg/kg/infusion) obtained by the groups of rats trained to self-administer under Cold (20 °C; N=12) or Hot (30 °C; N=11) ambient conditions in two-hour sessions. The schedule of reinforcement was FR5 for these studies meaning that each infusion required that the rat make five lever presses. As is obvious from the figure, the Hot group obtained more infusions of MDMA than did the Cold group. On session 16 only the drug-free vehicle was available and the increased responding (“saline bursting”) can be interpreted as a sign of drug-seeking behavior. This is particularly important for the Cold group given their very low (but consistent) numbers of infusions obtained. So to this point of the study, the behavior replicates and extends the work of Cornish and colleagues in 2003. They trained their rats in a lower ambient condition and then did post-acquisition tests at a higher ambient temperature and so the effect of ongoing experience in cold versus hot conditions could not be assessed. Interestingly, however, Feduccia and colleagues (2010) did a study much more like ours in design and failed to find any difference in the acquisition of IVSA in cold versus hot ambient conditions. There are a few procedural differences which may explain the difference in outcome but additional experiments would be required for firm conclusions. One potential difference is the selection of FR1 reward contingency which led to similar behavior in the MDMA groups and the groups allowed to self-administer saline only in that study. Although we did not have saline-only controls, our lever discrimination remained over 80% in both groups. In Aarde et al (2013) we ran a saline-only control group, pretrained to lever press for food at FR5, at normal laboratory ambient temperature (24 °C) and showed that lever discrimination breaks down significantly within the first 10 sessions of saline IVSA.

As outlined above, we were interested in the nature of the body temperature response during self-administration and how this might be changed by different ambient temperature conditions. Feduccia and colleagues had found no change in body temperature induced by MDMA IVSA at all, but their monitoring was via pre- and post-session rectal sampling. The temperature response to MDMA in rats is transient and it was likely that the sampling at 2 hours after the start of the session missed the dynamic response. This technique also requires handling the rats which can cause a stress response which may increase the body temperature. Our study used implanted radiotelemetry to observe the temperature response during the session. This adaptation of a figure from the paper presents 30 min averages (data collected every 5 minutes) of body temperature across the self-administration session and for one hour after the drug was no longer available. The daily responses are collapsed across blocks of 5-6 sequential training days. The takeaway here is that body temperature decreased in both Hot and Cold groups during the initial hour of the self-administration session and this response was gradually blunted in the Hot group across the self-administration training. The similar degree of hypothermia early in the acquisition phase and the course of tolerance versus drug intake in the Hot group was not consistent with our original hypothesis. It looked much more as though MDMA caused hypothermia under all training conditions and any attenuation of that response followed, rather than caused, increased drug intake over time.

To further probe the role of ambient temperature we next switched the temperature conditions and found that MDMA IVSA was unchanged within the groups. As if they’d been set on a preference trajectory. The failure to increase drug intake in the Cold group when placed in higher ambient temperature conditions was discordant with the original Cornish finding and we do not know why this might be the case. Most importantly, the Hot-trained group self-administered more drug in Cold ambient then did the Cold-trained group in Hot ambient and developed a more pronounced drop in body temperature. This showed that the ongoing self-administration training did not categorically alter the temperature response to MDMA in these animals.

The last study in the self-administering groups examined the effect of non-contingent administration of a range of MDMA doses (1-5 mg/kg, i.v.) on the body temperature response under Hot and Cold ambient temperature conditions. Up to this point, the animals self-selected their doses and so the interaction of dose with the temperature responses could not be easily disentangled. This last study found that hypothermia depended on dose, ambient temperature and the prior MDMA intake of the rat. Those individuals who self-administered very low amounts across the study (regardless of ambient temperature condition) were most sensitive to MDMA-induced hypothermia. Hypothermia was produced in both subgroups under Cold ambient, albeit to a greater degree in the animals with less cumulative MDMA intake. The takeaway from this part of the study is less clear cut. Clearly the hypothermic response to  MDMA under low ambient temperature conditions was only quantitatively, not categorically, altered in rats that self-administered more MDMA. Temperature responses under higher ambient temperature conditions were blunted- to the point that 3-5 mg/kg MDMA, i.v., did not change body temperature from baseline in the higher preference subgroup and while 2-3 mg/kg lowered body temperature in the lower-preference subgroup, 4-5 mg/kg did not.  [In general, the dose-effect relationship for MDMA-induced hypothermia does not reflect across Cold and Hot ambient temperatures. A high MDMA dose produces both less hypothermia under Cold conditions and increased hyperthermia under Hot conditions. Likewise, a moderate dose produces less hyperthermia in Hot conditions and more hypothermia in Cold ambient temperature conditions.] Thus, these data allow for the possibility that incremental blunting of the hypothermic response to MDMA may have some effect on sustaining IVSA behavior. Still, the overall thrust of this study suggests that the body temperature response is not a primary driver of self-administration of MDMA.

An additional study examined the effect of MDMA on intracranial self-stimulation (ICSS) reward in a different group of animals with no MDMA self-administration history. In ICSS the animal makes behavioral responses in response to small amounts of electrical current delivered to a specific region of the brain. We used a thresholding procedure in which the amount of current required for the animal to feel a rewarding effect can be determined from day to day. This procedure has been used by many laboratories over decades to show that treatments that make the animal feel good (such as an injection of methamphetamine) lower reward thresholds whereas conditions that make the animal feel bad (such as drug withdrawal in a dependent rat) lead to increased reward thresholds. Our study found that thresholds were increased merely by being placed in a hot environment (these data are all relative to individual thresholds from a 24 °C uninjected test session). Under Cold conditions, a 2.5 mg/kg MDMA, i.p., injection reduced reward thresholds in a manner consistent with the effects of methamphetamine, MDPV or mephedrone (Nguyen et al, 2016). Under Hot conditions, the same MDMA dose only returned reward thresholds to a baseline established under 24 °C without producing a pro-reward effect.

 

This ICSS experiment supports an interpretation of increased MDMA self-administration under high ambient temperature conditions as a normalization of negative affect, rather than an enhancement of the positive, feel-good subjective effects of MDMA.

September 21, 2017

Locomotor and Reinforcing Effects Of Pentedrone, Pentylone and Methylone

Filed under: Cathinones, Methylone — mtaffe @ 9:59 am

Pentylone and pentedrone are designer drugs within the cathinone stimulant class of drugs that are often referred to as “bathsalts”. These two entities have appeared in the recreational user populations as confirmed by results from ecstasydata.org, a review of trip reports on bluelight.org and erowid.org, as well as in a few scientific reports.

Second-generation substituted cathinone drugs such as pentylone and pentedrone have received less research attention compared with first generation bathsalts such as mephedrone and, in particular, methylone. This is sufficient motivation to explore the abuse liability and other properties of the more recently emerged drugs. In addition, this growing diversity of cathinone derivatives allows us to further determine the role of various structural substitution elements that may be common to both amphetamine and cathinone drugs of abuse. In this study, we investigated the 3,4-methylenedioxy motif  in the contrast of the effects of pentedrone with pentylone. This motif, when added to methamphetamine to produce MDMA, confers reduced rewarding potency and efficacy, reduced locomotor potency, reduced efficacy to induce stereotyped, repetitive behavior and increased thermoregulatory disruption. In contrast, the presence of the 3,4-methylenedioxy substitution produces no change in vivo in the context of the closely related, restricted transporter inhibitor cathinones α-PVP and MDPV which exhibit similar efficacy and potency on both locomotor and self-administration assays in rats . Pentedrone and pentylone also include the extended alkyl-tail carbon chain that is present on MDPV and α-PVP which may be related to the restriction of those drugs to transporter inhibition. This might predict that the 3,4-methylenedioxy motif has minimal impact on these additional compounds (which lack the pyrrolidine ring of MDPV and α-PVP).

The following has recently been accepted for publication:

Javadi-Paydar, M., Nguyen, J.D., Vandewater, S.A., Dickerson, T.J., and Taffe, M.A. Locomotor and Reinforcing Effects Of Pentedrone, Pentylone and Methylone In Rats. Neuropharmacology, doi: https://doi.org/10.1016/j.neuropharm.2017.09.002. [ Publisher Site ][ PubMed ]

We assessed locomotor activity changes produced by i.p. injection of Pentylone and Pentedrone in contrast with the effects of Methylone. This was conducted in a group of female rats (N=8) prepared with radiotelemetry devices which report both both temperature and an activity rate within a housing chamber. These studies found that 1 mg/kg of any of these drugs was insufficient to significantly increase activity, however increases were observed for 5 or 10 mg/kg of each compound. There were similar dose-effect relationships found in a group of male rats.

There was no sign of the type of reduction in activity that is often seen after high dose methamphetamine in the ~5-10 mg/kg range. Such reductions are produced because the rat is engaged in stereotyped, repetitive behaviors (called “stereotypy”) which resolve over the course of about 90-120 minutes, depending on dose, whereupon a boost in activity is often observed. This pattern we are reporting here is, however, fairly consistent with what would be observed for MDMA in this 5-10 mg/kg dose range. So these results are as would be predicted from the pharmacology and by reference to the better-studied entactogen compound, MDMA.

 

We also assessed drug self-administration by way of conducting dose-substitution under Fixed Ratio 1 (FR1) conditions. (Each lever press results in an infusion of drug.). This was conducted in a group of female rats who had been trained originally with alpha-PVP (N=4) or Pentedrone (N=6), but this training history was essentially irrelevant to the dose-response and is not separated for the analysis.

In this figure we depict the mean infusions of the three drugs that are obtained across a range of doses.  A significant difference from vehicle is indicated with *, from the 0.025 mg/kg dose with &, from the 0.05 mg/kg dose with §, from the 0.30 mg/kg dose by % and a significant difference from methylone and α-PHP, respectively, is indicated with #. The takeaway points are first that the ascending and descending limbs of the typical “inverted-U” dose effect function have been captured. This is important to enhance confidence that you are not missing a dose that would engender peak responding. So the essentially parallel curves for Methylone and Pentylone can be interpreted as nearly identical potency of the drugs. Pentylone is more effective, as can be interpreted by the fact the curve is shifted upwards, relative to the one for Methylone. In contrast, the peak for Pentedrone is at a lower dose, indicating that this compound is more potent. The efficacy is not clearly different from either other drug as the curve falls somewhat in between in terms of the peak number of infusions obtained.

 

Overall this study confirms that differences between Pentylone and Pentedrone are subtle and they exhibit a profile of dose-effect relationships that is as would be predicted for entactogens. Therefore the 3,4-methylenedioxy motif appears to convey little difference in the context of this core structure. There is some evidence for enhanced abuse liability relative to Methylone and this will be of great interest to follow up with additional models. The difference between Pentylone and Methylone lies in the presence of the extended alpha alkyl chain which enhances lipophilicity, potentially letting Pentylone enter the brain more rapidly.

May 22, 2017

Congressional Outreach

Filed under: ASPET, Experimental Biology / ASPET, Op/Ed, Public Health — mtaffe @ 11:53 am

We are very proud to announce that Jacques D. Nguyen, PhD,  was selected by the American Society for Pharmacology and Experimental Therapeutics (ASPET) to participate in their Washington Fellows Program for 2017. Jacques has been a very productive member of the Taffe Laboratory since joining it as a postdoctoral trainee in early 2015 and he still manages to find time to think about broader issues of science policy. He has been an active participant in ASPET as an academic society in addition to presenting work at the annual meetings.

Jacques is pictured, in this photo, preparing to discuss science policy with the staff of a San Diego Congressman,  Rep. Scott Peters.

For a little bit of background, the ASPET Washington Fellows Mission statement:

Program Mission

The mission of the ASPET Washington Fellows Program is to enable developing and early career scientists interested in science policy to learn about and become more engaged in public policy issues.

Fellows will develop an understanding of how public policy decisions made in Washington help shape and impact science policy, such as funding for the National Institutes of Health and other science agencies. Fellows will also learn how to advocate effectively on Capitol Hill and in their home districts.

This program will help fellows develop the skills and insights to become future leaders in science. 

 

April 13, 2017

Pre-Prints

Filed under: Careerism, NIH — mtaffe @ 10:11 am

In 2017 the NIH issued NOT-OD-17-050 Reporting Preprints and Other Interim Research Products to encourage funded investigators to speed the dissemination of tax-payer funded research by citing and claiming pre-prints as products of NIH funding.

The NIH encourages investigators to use interim research products, such as preprints, to speed the dissemination and enhance the rigor of their work. This notice clarifies reporting instructions to allow investigators to cite their interim research products and claim them as products of NIH funding.

Pre-prints are manuscripts (and other interim research products) which have not undergone peer-review and formal acceptance for publication.

The most critical implication of this new policy is for grant preparation.

Interim research products can be cited anywhere other research products are cited.  These sections include the following:

The benefits should be clear. Instead of having to describe work as being “in preparation” or “submitted” one can now point to a link and any interested reviewers can see it for themselves. This will be critical on the CV or Biosketch of junior scientists in transition. The publishing timeline is slow compared to their needs with respect to finding a postdoc appointment after graduate school, winning a fellowship as a postdoc or getting a job offer after postdoctoral training.

This will potentially help all PIs with their grant applications as well. Productivity can be a major point of review for new applicants, for renewal applications and indeed for any application if a PI is perceived to have too much funding. Productivity as reflected in peer reviewed published papers is not always under the direct control of the research team- the publication racket can induce significant unexpected delays. This pre-print policy allows the grant applicant to post pretty much anything that they want. It will potentially function as a hybrid of Preliminary Data and Publications. “Potentially” because there is no obligation for any reviewer to consider these documents.

I have decided to respond to this new initiative, for now, by submitting manuscripts to bioRχiv (http://biorxiv.org). I have found the submission process to be relatively easy on the scale of the usual manuscript submission for publication or to the PMC repository. The first two I submitted were available online within 24 h of my upload.

The critical question for most of us will be to try to determine what our threshold should be for publicizing any pre-print or interim research product. I have come to the conclusion that a manuscript that we have already submitted for publication somewhere clearly fits the bill as a sufficiently complete work to put on a pre-print server. A manuscript that we plan to submit for peer review essentially concurrently is also very clearly sufficient and the only difference here, to my view, is whether we are really, really at a submittable-draft stage or maybe jumping the gun with the pre-print.

The following three manuscripts had already been reviewed by the time I put them up on bioRχiv. I would characterize two of the reviews as being concerned about interpretation of the data in a way that would require a LOT more data to satisfy. This appears to me to satisfy one potential goal of posting pre-prints. I.e., that people can interpret the quality and meaning of the data for themselves before the authors manage to satisfy all theoretical concerns, sidelines or unlikely possibilities that might be required for publication acceptance. The third one is awaiting one more figure of data for the resubmission. We thought we had a decent rebuttal without it, one that would possibly fly with the editor. But we are also generating new data that is relevant. This has been slower to emerge than I had hoped and we have noticed some recent publication activity in this area. Posting this manuscript as a pre-print is essentially putting down a priority marker at this time.

Javadi-Paydar, M., Nguyen, J.D., Grant, Y., Vandewater, S.A., Cole, M., and Taffe, M.A. Effects Of Δ9-THC And Cannabidiol Vapor Inhalation In Male And Female Rats.  bioRχiv, 2017, Posted April 18, 2017 doi:

Taffe, M.A. Wheel running increases hyperthermia and mortality rate following 3,4-methylenedioxymethamphetamine (MDMA) in rats. bioRχiv, 2017, Posted April 11, 2017 doi:

Aarde, S.M., Huang, P-K  and Taffe, M.A. High Ambient Temperature Facilitates The Acquisition Of 3,4-Methylenedioxymethamphetamine (MDMA) Self-Administration. bioRχiv, 2017, Posted April 4, 2017 doi:

 

March 19, 2017

Vaccination against methamphetamine works in female rats

Filed under: Methamphetamine, Vaccines, Vape inhalation, Vapor Inhalation — mtaffe @ 9:32 am

We have shown that a vaccine designed to blunt the effects of methamphetamine works in male rats in two prior publications, summarized here and here. We have also had success showing that vaccines directed against the synthetic cathinones MDPV (“bathsalts”) and alpha-PVP (“flakka”) work to reduce the effects of those drugs. A brief video outlining the approach to generating vaccines that might be helpful for drug abused created by NIDA can be found here.

The following has recently been accepted for publication:

Nguyen, J.D., Bremer, P.T., Hwang, C.S., Vandewater, S.A., Collins, K.C., Creehan, K.M., Janda, K.D. and Taffe, M.A. Effective active vaccination against methamphetamine in female rats, Drug Alcohol Depend, 2017, 175:179-186. [Publisher Site] [PubMed]

In this study we show that an increase in the amount that female rats move around their cages after an injection of methamphetamine is reduced in the MH6-KLH vaccinated rats.

As you can see in the explainer video, the main principle of anti-drug vaccination is that antibodies can bind some of the drug molecules (methamphetamine in this case) in the bloodstream, thereby preventing them from getting into the brain. This capacity to retain methamphetamine is relatively fixed at a given point in the vaccine sequence, thus administering a sufficiently high dose can (should) overcome the protection.

In our data, the effects of the vaccine were dose dependent. This is Figure 4 from the paper which depicts locomotor activity rates (counts per minute) in the MH6-KLH and KLH groups in the first and second hours after injection of methamphetamine in three doses [Significant differences from the Vehicle and 0.25 mg/kg within Group and Hour are indicated by §, from Vehicle (only) by # and from the 0.5 mg/kg condition by &. ]. There is a dose-dependent increase in activity rate compared with the vehicle injection condition. With respect to the active vaccination group, complete protection was found at the 0.25 mg/kg dose and partial protection at 0.5 mg/kg compared with the KLH group; the two groups were about the same after 1.0 mg/kg was injected. This further enhances our ability to interpret these data as a specific effect of the vaccination and to determine where the threshold for effective protection may lie.

There was another finding in this study which was slightly disappointing in terms of the vaccine study but greatly enhanced our understanding of another thing that we have been working on, namely vapor inhalation techniques to deliver drugs to rats for various research purposes. Most specifically we showed that e-cigarette type vapor inhalation of methamphetamine (and MDPV and mephedrone) increases the activity of male rats to a similar extent as it does when injected (blogpost overview). We used this model in the present study as well and confirmed that just as with male rats, the female rats activity in the cage was increased after vapor inhalation of methamphetamine to about the same extent as after the injected doses. Therefore up to this point in time we were assuming that the dose delivered to the rat was approximately similar when similar behavioral results were produced.

Unfortunately there was no difference in the effects of inhaled methamphetamine across the vaccinated and control groups of rats. We originally interpreted this as potentially a difference in the rate of drug penetration into the brain which minimized the ability of the vaccine-generated antibodies to prevent locomotor effects.

Upon reviewer request we then examined the blood levels of methamphetamine after injection (0.25, 1.0 mg/kg, i.p.) and the inhalation condition in a different group of unvaccinated female rats. We found that methamphetamine was about ten times higher in the blood after inhalation versus injection in this new study. This of course explains why the vaccinated group was not protected, i.e., the dose under inhalation was far past the ability of the antibodies to sequester in the bloodstream.

The curious thing is still why a similar level of locomotor activity was produced at the 10-fold difference in methamphetamine levels. Very likely this is due to the rate at which drug is delivered to the animal- in our inhalation model this takes place over 30 minutes whereas an injection takes seconds. Obviously one of our next avenues of research is to better determine the way that drug levels increase in the blood during vapor inhalation.

January 2, 2017

Current Topics in Behavioral Neurosciences on Novel Psychoactive Substances

Filed under: 4-MMC/Mephedrone, Cannabimimetics, Cathinones, IVSA, MDPV, Methylone — mtaffe @ 2:08 pm

There is a new Current Topics in Behavioral Neuroscience book on New and Emerging Psychoactive Substances that has been organized by Michael H. Baumann, Ph.D., of the Intramural Research Program of the National Institute on Drub Abuse. This editorial effort resulted in 18 chapters on various topics of interest which are now available online.

Chapter 1: Madras, B. The Growing Problem of New Psychoactive Substances (NPS) [link]

Chapter 2: Glennon, R.A. and Dukat, M. Structure-Activity Relationships of Synthetic Cathinones [link]

Chapter 3: Simmler, L.D. and Liechti, M.E. Interactions of Cathinone NPS with Human Transporters and Receptors in Transfected Cells [link]

Chapter 4: Solis, E. Electrophysiological Actions of Synthetic Cathinones on Monoamine Transporters [link]

Chapter 5: Baumann, M.H., Bukhari, M.O., Lehner, K.R., Anizan, S., Rice, K.C., Concheiro, M. and Huestis, M.A. Neuropharmacology of 3,4-Methylenedioxypyrovalerone (MDPV), its Metabolites, and Related Analogs [link]

Chapter 6: Negus, S.S. and Banks, M.L. Decoding the Structure of Abuse Potential for New Psychoactive Substances: Structure-Activity Relationships for Abuse-Related Effects of 4-Substituted Methcathinone Analogs [link]

Chapter 7: Watterson, L.R. and Olive, M.F. Reinforcing Effects of Cathinone NPS in the Intravenous Drug Self-Administration Paradigm [link]

Chapter 8: Aarde, S.M. and Taffe, M.A. Predicting the Abuse Liability of Entactogen-Class, New and Emerging Psychoactive Substances via Preclinical Models of Drug Self-administration.[link]

Chapter 9: King, H.E. and Riley, A.L. The Affective Properties of Synthetic Cathinones: Role of Reward and Aversion in Their Abuse [link]

Chapter 10: Kiyatkin, E.A. and Ren, S.E. MDMA, Methylone, and MDPV: Drug-induced Brain Hyperthermia and its Modulation by Activity State and Environment [link]

Chapter 11: Angoa-Pérez, M., Anneken, J.H., Kuhn, D.M. Neurotoxicology of Synthetic Cathinone Analogs [link]

Chapter 12: Wiley, J.L, Marusich, J.A. and Thomas, B.F. Combination Chemistry: Structure–Activity Relationships of Novel Psychoactive Cannabinoids [link]

Chapter 13: Tai, S. and Fantegrossi, W.E. Pharmacological and Toxicological Effects of Synthetic Cannabinoids and Their Metabolites [link]

Chapter 14: Järbe, T.U.C. and Raghav, J.G. Tripping with Synthetic Cannabinoids (‘Spice’): Anecdotal and Experimental Observations in Animals and Man [link]

Chapter 15:Halberstadt, A.L. Pharmacology and Toxicology of N-Benzylphenethylamine (“NBOMe”) Hallucinogens [link]

Chapter 16: Papaseit, E., Molto, J., Muga, R., Torrens, M., de la Torre, R. and Farre, M. Clinical Pharmacology of the Synthetic
Cathinone Mephedrone [link]

Chapter 17: Mayer, F.P., Luf, A., Nagy, C., Holy, M., Schmid, R., Freissmuth, M., Sitte, H.H. Application of a Combined Approach to Identify New Psychoactive Street Drugs and Decipher Their Mechanisms at Monoamine Transporters [link]

Chapter 18: Schifano, F., Orsolini, L., Papanti, D., Corkery, J. NPS: Medical Consequences Associated with Their Intake [link]

 

December 9, 2016

Vaccination against the effects of MDPV (“bathsalts”) and alpha-PVP (“flakka”)

Filed under: alpha-PVP, Cathinones, MDPV, Vaccines — mtaffe @ 10:10 am

The substituted cathinone stimulants 3,4-methylenedioxypyrovalerone (MDPV) and alpha-pyrrolidinopentiophenone(alpha-PVP) have emerged as significant public health concerns in recent years. These drugs turned out to be monoamine transporter inhibitors with high selectivity for the dopamine transporter. These two compounds lack the monoamine releasing properties of methamphetamine, MDMA and other recently popular cathinone derivatives such as mephedrone and methylone. As we’ve shown, both MDPV and alpha-PVP are highly reinforcing in the rat self-administration paradigm and increase locomotor behavior when injected non-contingently or inhaled with e-cig technology. Although these drugs are still in the early stages of market penetration, the data from our lab as well as several other labs suggest that these will have high abuse liability. Effective countermeasures are therefore likely to be needed in the future.

One method to counteract effects of psychoactive drugs that has been attempted is vaccination; an explainer video from NIDA is available here. In this strategy a drug-like chemical structure is attached to a large protein that generates an immune response. When successful, this immune response creates antibodies that circulate in the blood with the capacity to recognize and bind to the target drug molecule. If this is done to effective levels, the administration of a given dose of drug leads to a reduced response, due to part of the drug dose being bound to antibodies in the bloodstream which prevents from entering the brain.

A paper describing an initial effort to develop a vaccine to provide protection against the effects of MDPV and alpha-PVP has recently been accepted for publication. As with all of our vaccine work to date, this was conducted in collaboration with the Janda laboratory at TSRI.

Nguyen, J.D., Bremer, P.T., Ducime, Creehan, K.M., Kisby, B.R., Taffe, M.A. and Janda, K.D. Active vaccination attenuates the psychostimulant effects of α-PVP and MDPV in rats, Neuropharmacology, 2017, 116:1-8. [PubMed][Publisher Site]

In this study, Paul Bremer and Alex Ducime created vaccine candidates designed to generate antibodies against MDPV and alpha-PVP, respectively. Initially, three groups of male rats were vaccinated to evaluate the MDPV-specific, alpha-PVP-specific vaccines against a group vaccinated with the immunogenic protein (keyhole limpet hemocyanin; KLH). The antibodies in the MDPV-vaccinated group showed high affinity for MDPV but not for alpha-PVP or methamphetamine. Likewise, the antibodies in the alpha-PVP group were selective for alpha-PVP over MDPV or methampetamine.

Brent Kisby, an undergraduate on an extended internship, in combination with Kevin Creehan and Jacques Nguyen first determined if these rats would exhibit functional protection against drug exposure. We selected a wheel-activity response to drug injection (see Huang et al, 2012) because this had proved effective at screening anti-methamphetamine candidate vaccines in our prior study (Miller et al, 2013).
nguyen17-alphavaccfig3-wheel This figure (click to enlarge) shows wheel activity (quarter revolutions) in the four hours following injection with four doses of alpha-PVP (Panels A, B) or four doses of MDPV (Panels C, D). The left hand panels depict the effects of drug in the KLH-only control groups while the right hand panels depict the effects of drug in the respective alpha-PVP-KLH and MDPV-KLH vaccine groups. The asterix indicates a significant change of activity relative to the vehicle (saline) injection condition. The takeaway message here is that doses of alpha-PVP (0.5, 1.0 mg/kg, i.p.) and MDPV (1.0 mg/kg, i.p.) which increase wheel activity in the control group do not do so in the respective vaccine group. The vaccine can be partially surmounted since the 5 mg/kg dose of each drug increased activity in the vaccinated rats, although this increase was numerically lower and lasted less long in the MDPV-KLH and alpha-PVP-KLH animals compared with the control group.

This promising result led to the design of an intravenous self-administration study to test the ability of alpha-PVP-KLH vaccination to alter the course of self-administration. Jacques Nguyen and Kevin Creehan headed up this study.
A group of rats were first trained to self-administer alpha-PVP, prior to any vaccination. This is only the second study to publish the acquisition of alpha-PVP self-administration in an animal model (see Aarde et al, 2015) and we found that a 0.1 mg/kg/infusion dose was required to produce good acquisition in Sprague-Dawley male rats. Thereafter the rats were placed on hiatus from drug self-administration and given a 5 week protocol of three immunizations, divided into two groups- one receiving KLH only and the other receiving alpha-PVP-KLH vaccine. We showed first that on return to self-administration at a reduced per-infusion dose of 0.025 mg/kg/infusion the alpha-PVP-KLH vaccinated animals self-administered more drug. This result is consistent with the circulating antibodies producing partial reduction of the dose as it was self-administered and the corresponding behavioral compensation to produce similar brain levels of drug.
nguyen17-fig7-prepostAfter three weeks the animals were given a booster immunization which resulted in about a doubling of the circulating antibody level (titer). This resulted in no change in the KLH-only animals’ drug intake, however the alpha-PVP-KLH animals changed from a mean of 17-20 infusions per session to a mean of about 4-5 infusions per session, a significant reduction in self administration. This lasted for 15 sessions and is depicted in the figure (click to enlarge) as Post4-Post8 bins of three sequential sessions.

As discussed in the paper this is an initial feasibility study but it shows the potential of the anti-drug immunotherapy strategy to be effective against the effects of both MDPV and alpha-PVP. This should encourage additional work to determine the extent and nature of the protection against these substituted cathinone stimulants that can be achieved with vaccines.

These studies were funded by USPHS grants DA024705, DA042211 and DA037709.
__
Additional Reading: A list of our cathinone-related publications can be found here.

December 3, 2016

New Chapter on Entactogen Self-Administration

Filed under: 4-MMC/Mephedrone, alpha-PVP, Cathinones, MDPV, Methylone — mtaffe @ 2:48 pm

We have recently published a short review on the self-administration of entactogen psychostimulants.

Aarde, S.M. and Taffe, M.A. Predicting the Abuse Liability of Entactogen-Class, New and Emerging Psychoactive Substances via Preclinical Models of Drug Self-administration. Curr Top Behav Neurosci. 2016 Dec 2. [Epub ahead of print] [PubMed][Publisher Site]

This is part of a Current Topics in Behavioral Neuroscience book on New and Emerging Psychoactive Substances organized by Mike Baumann of the NIDA IRP who has been publishing a lot of work on synthetic cathinones lately. Eventually the Chapters will be collected into a book and assigned unique pagination.

For now you can look chronologically in the pre-publication OnlineFirst list.

The first chapter of the series that was published was:
Schifano et al “NPS: Medical Consequences Associated with Their Intake” [link]

The cannabinoids are covered:
Wiley, Marusich and Thomas Combination Chemistry: Structure–Activity Relationships of Novel Psychoactive Cannabinoids [link]

All told there will be around a dozen chapters, I think most of them are on the pre-print list already. Happy reading!

November 3, 2016

Thoughts on Proposition 64 to Legalize Recreational Marijuana in California

Filed under: Cannabis — mtaffe @ 10:41 am

I wrote a brief note on Facebook the other day to outline what I thought were several points that come up when people in the community ask me about the upcoming vote on recreational marijuana (link to ballotpedia summary of Prop 64). This was picked up in a post at Forbes by David Kroll (a handy summary video is here)

This piece was noticed by Sasha Foo at KUSI and she was kind enough to film a news segment which aired on 2 November, 2016. This links to the 6 pm broadcast version.

My Facebook remarks (with a few key links to data sources added):

I’m in California which will be voting on Proposition 64 which legalizes recreational marijuana. As many of my friends, neighbors and acquaintances are aware that I work in the substance-abuse fields of science, they have questions. So I thought I would put some of my usual responses/points down on a Fb post.

First, some background on my opinions. I work for you, the taxpayer of the US. This is because my work is funded by grants from the National Institutes of Health. Because these are primarily from the National Institute on Drug Abuse, my role is to investigate the effects of recreational drugs on the brain (and the rest of the body) with some attention paid to how this might affect the health of humans.

This is most emphatically not a policy role. I have no special expertise on public policy and my comments are not meant in that way. I do hope that science can be used to inform policy and, frankly, I wish that public policy across the board paid a lot more attention to facts and data. This is not to say, however, that I believe that the facts necessarily lead all interested people to the same *policy* decision. Because policy requires the weighing of factors and pitting positives and negatives of various kinds against each other.

As far as legalizing recreational marijuana goes, I do think that the epidemiological, human laboratory and animal laboratory data has some relevance to the Prop 64 issues. So, I’m going to list a few facts.

1) Marijuana is addictive. Full stop. The conditional probability of dependence is about 9% where like-to-like comparisons put cocaine and methamphetamine at 15%, heroin at 25-45% (data are terrible) and alcohol at 4%. Alcohol is a huge problem because 85%+ of people consume it at least annually. In contrast, less than 1% of people have ever tried heroin, 0.4% in the past year. Marijuana comes in at about 32% annual prevalence for ages 19-28. The scope of the addiction issue depends on how many people are using it, obviously. This will go up with legalization- but we don’t have any idea how much.

2) 5-6% of high-school seniors use Marijuana daily. Daily. That’s the US average. I don’t have numbers for California. http://www.monitoringthefuture.org/data/15data/15drfig4.pdf

3) Marijuana addiction is as “real” as any other. Frequency of withdrawal symptoms and severity of those symptoms were compared between marijuana and tobacco smokers and the data were nearly indistinguishable. Most people are much more familiar with nicotine dependency (which is a higher rate, btw, probably 33%+) since it is more common, not embarrassing to discuss in public and is conventionally recognized. A lack of personal familiarity with the scope of withdrawal in the people who are marijuana dependent doesn’t mean that it doesn’t exist.

4) There is no such thing as “psychological” versus “physical” dependence since the brain is part of the body and the mind is the functioning of the brain. Keep in mind that people can be months to years out from their last use of any drug and still relapse severely. This is not being driven by the withdrawal symptoms that most everyone recognizes when they talk about “physical” dependence.

5) Marijuana acutely impairs cognitive and other behavioral functions.

6) Behavioral tolerance with chronic exposure is substantial. Blood levels of THC in animals or humans are a poorer proxy for impairment (versus other drugs) if you do not know anything about the prior exposure history.

7) THC is detectable in the body for a very long time compared with many other drugs of abuse. One study found detectable THC, or one of the main metabolites, for 30 days of in patient study (chronic users).

8) Trying to make specific predictions about an individual who uses marijuana from general findings (there is always a central tendency or average around which the distribution of data points or individual outcomes varies) is a fools’ errand. We can only predict general trends. Conversely, and this is important for your personal introspection, the evidence from one given data point or individual doesn’t tell us much that is informative about the average trend. The fact that it is your personal experience does not make it more valid.

Finally, there is much we simply don’t know. Any given scientific study or data set is limited by how it was generated. This doesn’t mean we throw up our hands and say it is all bunk or uninterpretable but it means one does have to think about it a bit.

I would invite you to read over the Prop 64 provisions. Personally, I see a fair bit of investment of the tax revenue in state sponsored activities to answer some of these issues better, to address some of the obvious concerns, etc. To me this is a positive. The extent to which this will happen, the extent to which actionable information will result, the extent to which activities intended to head off or ameliorate obvious negatives is, however, an unknown.

Older Posts »

Blog at WordPress.com.