TL neuro

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. 

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.

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September 21, 2015

MDMA purity in Ecstasy 2013 to 2015

Filed under: MDMA — mtaffe @ 12:21 pm

I was just looking at the ecstasydata.org data on the content of pills submitted for analysis to see what new cathinones were turning up. While there, I did a little search on pills that were found to contain MDMA. There is a common thought that Ecstasy pills are notoriously contaminated with non-MDMA psychoactive drugs, supported by the data places such as ecstasydata.org have generated. My dabbling in the database in the past has my memory thinking that it was never any worse than about 50% of submitted pills that were positive for MDMA containing other drugs.

[Note, as always that this is not in any way a representative sample. It depends on voluntary submission of pill samples and it can, obviously, only ever cover a tiny fraction of what is being sold on the clandestine market at any time. There are arguments to be made that severe selection biases might creep in- from the type of people who bother to submit pills, or know about the service, to a possibility that those pills reputed to be suspicious in subjective outcome might be more likely to be submitted. So take this with caution.]

what was interesting is that when I limited the search parameters to 2013-2015, there were 285 entities with MDMA-only and 387 with MDMA+something else. Thus, 74% of the submitted items that contained MDMA were pure. It’s 85% in 2015, to date.

2000-2002: 80%
2003-2005: 53%
2006-2008: 31%
2009-2011: 46%
2012: 60%

So the purity of MDMA-containing street drugs appears to have rebounded across this 15 year interval.

I wonder how this is related to the MDMA-drought that heralded the onset of popularity of mephedrone and methylone and the “Molly” marketing situation by which consumers think they are getting the pure molecule, i.e., MDMA.

August 19, 2015

Mephedrone is also more reinforcing than MDMA or Methylone in male rats

Filed under: 4-MMC/Mephedrone, Cathinones, MDMA, Methylone — mtaffe @ 2:30 pm

StructureFig-MDMA-Methylone-MephedroneMethylone has now surpassed MDMA in Forensic Laboratory samples in the US. Mephedrone is less popular in the US but maintains a high degree of popularity in the UK. We recently published a paper [Creehan et al, 2015; PubMed; blogpost] showing that the drug mephedrone was a more effective reinforcer than either MDMA or methylone in female rats.

Our followup study which compared the self-administration of these three drugs in male rats has been accepted for publication.

Vandewater, S.A., Creehan, K.M. and Taffe, M.A. Intravenous self-administration of entactogen-class stimulants in male rats. Neuropharmacology, 2015, 99:538-545. [ PubMed ][ Publisher Site ]

We are interested in the reinforcing potential of mephedrone and methylone due in large part to their neuropharmacological similarity to MDMA. Specifically, these three drugs have a relatively greater enhancement of serotonin in the nucleus accumbens of the rat brain compared with the enhancement of dopamine. The latter effect is associated with pleasurable/rewarding effects of traditional stimulant drugs like methamphetamine whereas the preferential serotonin release/accumulation is associated with reduced reward potential. In short, rats have shown much less intravenous self-administration of MDMA versus methamphetamine.

Fig1-XY-3drg-Acq The fact that Mephedrone and Methylone share the MDMA-like neurochemical profile groups them all together as atypical or entactogen-class stimulant drugs and predicts less compulsive use compared with traditional stimulants like methamphetamine. Yet several self-administration studies with mephedrone have already shown a greater abuse potential compared with MDMA. The one available study with methylone (Watterson et al, 2012; blogpost) prior to our work implied the same. Our study in female rats was the first to directly compare these three drugs and we confirmed that mephedrone is a much more effective reinforcer, thus predicting higher liability for compulsive use. MDMA and methylone, however, appeared to be quite similar.

Our new study in the male rats used essentially the same procedures as the study in females and had the same conclusion. In this figure we show mean (±SEM) daily infusions of drug (upper panel) and the proportion of responses on the drug-associated lever versus the inactive lever (lower panel) obtained for groups of male rats trained to self-administer MDMA (N=17), Methylone (N=14) or Mephedrone (N=15) in 2 hour sessions. [Significant differences from the first session within group are indicated by *, differences between mephedrone and both other groups by #, differences from methylone by ‡ and differences from MDMA by †.] The MDMA and mephedrone groups differed from each other and the methylone-trained group was intermediate.

The results from the female animals in the previous study differed slightly in that the methylone and MDMA intakes were nearly identical and were both significantly different from the mephedrone self-administration.

MDMA-Methylone-AcqWe did some follow up comparisons between males and females for the new paper and those ended up in the Supplemental Materials file. The only significant sex-difference was for the MDMA-trained groups where there was a significant main effect of rat sex confirmed in the analysis. The methylone intakes appeared to be nearly identical between males and females, as is depicted and the mephedrone intakes did not differ either (not shown).We did some further sub-groups analysis and found that this difference in MDMA self-administration was mostly in the less-preferring half of the male group.

At this point we have a direct confirmation of the enhanced liability of mephedrone for compulsive use over that of MDMA. This is a clear rejection of the suggestion based on intra-cranial self-stimulation reward data that it has reduced liability- clearly something is off about the way the results were interpreted by Bonano et al (2014). Methylone appears to be much more similar to MDMA although it might be a slightly more effective reinforcer in male rats. Nevertheless we still cannot reconcile our results with methylone self-administration with the apparently robust self-administration reported by Watterson et al (2012). As there are only now three published studies of the self-administration of methylone, we must await further studies to better understand the reasons for these different outcomes.

May 6, 2015

Methylone is replacing MDMA in Forensic Laboratory samples

Filed under: alpha-PVP, Cathinones, MDMA, MDPV, Methamphetamine, Methylone — mtaffe @ 10:38 am

The National Forensic Laboratory Information System (NFLIS) is, according to the Introduction to the 2014 Mid-year report [PDF]:

a program of the Drug Enforcement Administration (DEA), Office of Diversion Control NFLIS systematically collects results from drug analyses conducted by State and local forensic laboratories These laboratories analyze controlled and noncontrolled substances secured in law enforcement operations across the country, making NFLIS an important resource for monitoring illicit drug use

I was curious to see what this particular dataset had to say about the emergence of substituted cathinone stimulants such as mephedrone, methylone, MDPV and alpha-PVP. We work on the effects of these drugs and it is of interest to monitor the evolution of their use with various epidemiological measures. This is but one such measure and the relative penetration of a given drug may differ depending on whether the measure is from law enforcement, surveys of adolescents, online surveys, etc.

NFLIS-summaryThe NFLIS appears to have started systematically assessing several cathinone drugs in 2011. Either that or they were too infrequent to make the specific tables presented in the reports. These are relatively low incidence, you will note. For comparison, methamphetamine accounts for about 10% of reports and did not change much across 2010 to 2012 when MDMA reports dropped significantly. I would have predicted, before seeing these data, that the incidence of MDMA was still higher than these newer drugs. This figure shows that methylone is now more frequently reported in NFLIS samples than is MDMA. Methylone is probably the most MDMA-like of the cathinones in terms of structure (it is the direct cathinone cousin, 3,4-methylenedioxymethcathinone), neuropharmacology and subjective effects (to the extent this has been assessed).
The second surprise for me was seeing that MDPV and alpha-PVP are less commonly reported than methylone. I would have expected these drugs to have a higher representation, based on the emerging profile as traditional stimulants that support highly repetitive use.

h/t: Forensic Tox Guy

March 16, 2015

Overnight Wheel Access Decreases Stimulant Self-Administration

Filed under: Cathinones, Exercise, MDMA, Methamphetamine, Methylone — mtaffe @ 10:57 am

env046-325x325The following has recently been accepted for publicationpublished:

Shawn M Aarde, Michelle L Miller, Kevin M Creehan, Sophia A Vandewater, Michael A Taffe. One day access to a running wheel reduces self-administration of d-methamphetamine, MDMA and Methylone, 2015, Drug Alcohol Depend, 151:151-158. [Publisher Site, PubMed]

   The laboratory continues to study the role that exercise can play in altering stimulant drug self-administration using rodent models. Our initial paper found that if rats have concurrent access to intravenous methamphetamine and an activity wheel, the drug intake is suppressed below that of animals who can only access an immobile, locked wheel (Miller et al, 2012; blog). In that study, however, unlocking the wheel had no effect on the methamphetamine  intake for those animals who had self-administered methamphetamine for 7-14 sessions without wheel activity.

   A study by Smith and Witte (2012; PubMed) showed that if rats are provided wheel access in their home cages they will self-administer less cocaine. That study maintained constant conditions for groups of animals, thus it was not determined if home cage wheel access could overturn an established self-administration pattern.

   In this new study we examined the effects of overnight wheel access in the vivarium home cage on the intravenous self-administration of three different stimulant drugs in four different experiments. The key feature for our experiment was that animals were trained to stable levels of self-administration of methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA) or methylone in the absence of significant prior wheel experience or any ongoing wheel access.

Aarde15-22hrWheelFig2   This figure (click to enlarge) depicts the mean number of infusions earned by groups of rats trained to self-administer A) methamphetamine (1 hr sessions; 0.05 mg/kg/inf; N=18), B) methamphetamine (2 hr; 0.05 mg/kg/inf; N=13), C) MDMA (2 hr; 0.5 mg/kg/inf; N=11) or D) Methylone (2 hr; 0.5 mg/kg/inf; N=12). Data are presented for each of the first four days (Monday-Thursday) in a week in which animals had no access to the activity wheel in the home cage (No Wheel) or were permitted to use the wheels (Wheel; grey and open bars) following the first (M; Monday) session of the week. Therefore the critical comparisons are Monday sessions (no wheel access prior) with the subsequent three days within the Wheel week and between T, W and Th sessions across Wheel and No-Wheel weeks. In the figure, significant differences from the first session within a week are indicated by * and significant differences between Wheel-access and No-Wheel weeks by #.

   The design was repeated-measures meaning that each rat participated in all the conditions. We used a 2 cohort crossover design for the most part, meaning that each experiment was split into two groups of rats with one receiving the Wheel Access week first and the other cohort receiving the No Wheel week first. This order did not make any difference in the effect of the wheel so the data are presented by Wheel-Access condition without respect to the order in which a given rat received the different conditions.

   The key takeaway message for this study is that wheel access in the ~22 h prior to a behavioral session is capable of significantly reducing the amount of drug rats will self-administer.

   This effect was replicated across four studies which varied in specific design, therefore we can conclude it is robust against methodological variation.

Implications:
   First, this is a confirmation of something that was made obvious by the Smith and Witte (2012) paper. There have been several papers that purport to show that a 6 week history of wheel access in the home cage prior to the initiation of drug self-administration training reduces drug intake. To the extent such models continue the wheel access during the self-administration training, they are confounded with the effect we have shown here. Consequently, neurobiological studies predicated on brain changes that require extensive exercise histories, such as neurogenesis processes, are likely to come up with negative results.

   Second, this study shows that it is possible for an activity intervention to reduce drug self-administration after a pattern of daily intake has been stabilized. It may not occur in every design but it is possible. This supports the further use of this model to study the ways in which exercise programs for human users might be best designed and applied. It even suggests that exercise programs can reduce drug use even without the subject having any intention to alter their use pattern.

Future Directions:
   There are numerous avenues to pursue in the wake of this study. From the behavioral perspective, we are not certain where, in the course of 22 hr of wheel access, the effect on drug intake lies. It is possible that this effect depends on activity early in the dark cycle (rats are nocturnal so this is their active part of the day), just prior to the self-administration session. It is also possible that wheel activity immediately after the last day’s session while acutely intoxicated on the stimulant is somehow aversive and thereby punishes subsequent drug taking. From a mechanistic perspective, it is pretty clear that the most profitable avenue is to follow up on the acute effects of exercise that emerge within a time frame no longer than about 22 hrs. The endogenous opioid systems are particularly attractive becuase of decades-old understandings that the so-called “runner’s high” may be mediated by such neurochemical systems.

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activity wheel picture from Med Associates, Inc

January 9, 2015

Mephedrone is more reinforcing than methylone or MDMA in female rats

Filed under: 4-MMC/Mephedrone, Cathinones, IVSA, MDMA, Methylone — mtaffe @ 9:27 am

A paper from the laboratory on the self-administration of MDMA-like cathinone drugs has been recently accepted for publication published online.

Creehan, K.M., Vandewater, S.A. and Taffe, M.A. Intravenous self-administration of mephedrone, methylone and MDMA in female rats. Neuropharmacology, 2015, 92:90-97. DOI: 10.1016/j.neuropharm.2015.01.003 [Publisher Link, PubMed]

 

This paper is the result of our “Open Experiment in Open Experimenting” which is chronicled on the linked page.
StructureFig-MDMA-Methylone-MephedroneBackground 1: Cathinones, aka “bathsalts”
There are a number of synthetic cathinone stimulants that are in reasonably substantial and continued use in the US, as well as elsewhere worldwide. Cathinone, the core molecule differs from amphetamine in the addition of a ketone in the beta position. In the figure, 3,4-methylenedioxymethamphetamine (MDMA or “Ecstasy”) can be contrasted with its cathinone cousing Methylone, which might otherwise be called 3,4-methylenedioxymethcathinone. If you see Methylone referred to as “bk-MDMA”, as it sometimes is with users, you will now be able to recognize what “beta-keto-MDMA” means. Mephedrone more or less led the emergence of substituted cathinones with one death noted in Sweden in 2008 and a major increase in prevalence in the UK throughout 2009 and 2010. To my view there has never been a major place in the recreational pharmacopeia for 4-methylmethamphetamine, the amphetamine cousin of mephedrone.

Background 2: Empathogenic or MDMA-like neuropharmacology
We have described in prior posts how mephedrone exhibits an MDMA-like trait of preferentially increasing serotonin versus dopamine overflow in the nucleus accumbens of rats; this is different from the dopamine-dominant response to methamphetamine or amphetamine. This pattern has been proposed to be intimately related to the fact that MDMA is only an uncertain reinforcer in rodent IVSA compared with the more typical amphetamines. Mephedrone is much more readily self-administered than MDMA and a single prior report seemed to indict that methylone likewise is an effective reinforcer in IVSA.

Background 3: Female animals
The NIH has recently issue a policy position which reinforces the critical importance of conducting sex-difference comparisons across biomedical domains (Clayton and Collins 2014). It has been shown that female rats will self-administer more cocaine (Roth and Carroll 2004b; Smith et al. 2011) and more methamphetamine (Reichel et al. 2012; Roth and Carroll 2004a) than males; these sex differences can be more pronounced under long-access escalation and/or Progressive Ratio procedures. Little is known about any possible sex differences in the self-administration of atypical stimulants like MDMA or the recently emerging MDMA-like designer cathinones. In short, we couldn’t find a single report of IVSA of any of these compounds in female rats (although Oakly et al, 2014 fails to specify the sex). Thus, the present study was conducted in female rats to expand understanding of the comparative reinforcing properties of these compounds.

 
Results
Creehan15-Fig2-infusionsThis figure from the paper (click to enlarge) illustrates the number of infusions of drug obtained by three groups of female Wistar rats during the acquisition phase of intravenous self-administration (IVSA). Each group was trained on a different drug. The take-away messages is in the upper panel. At equal training doses the rats trained on mephedrone (4-methylmethcathinone, 4-MMC) take more infusions across the training interval. [Significant difference from the first session within group by *, Between mephedrone and both other groups by #, versus methylone by ‡ and versus MDMA by †.].
The bottom two panels of the figure split the groups into the upper and lower halves based on average drug intake during the acquisition interval. The point of doing so is that the Schenk lab studies (here, here) have shown that ~40-50 percent of (male, normal or wild-type) rats will fail to meet their acquisition criteria for MDMA IVSA. This is unusual for stimulant IVSA- something like 80-100% would be more typical for cocaine. Instead of creating arbitrary “acquisition” criteria, we chose to report subgroup analyses (the paper also contains drug-associated lever discrimination ratio information). Mephedrone was still preferred by the lower-preference animals and we illuminated a small advantage for methylone IVSA in the more-preferring Upper Half compared with the MDMA trained animals.

Conclusions
This direct comparison paper verifies a picture which has been emerging with the nascent IVSA literature on mephedrone- i.e., that it is clearly more effective as a reinforcer compared with MDMA. This points back to the neuropharmacological effects outlined above (enhanced serotonin response in nucleus accumbens of rats) and raises new questions about the relevance of such properties in predicting abuse liability. Together, these behavioral findings oppose a claim advanced by Bonano and colleagues (2014) on the basis of intracranial self-stimulation reward data that mephedrone has decreased abuse liability relative to methylone and MDMA.

There is only the single other paper on methylone IVSA and our results do not concur with the findings of Watterson et al (2012). Obviously there are methodological differences so additional experiments will be needed to gain better clarity on the propensity of methylone to support IVSA compared with MDMA and mephedrone. There was a hint in our data that for the more-preferring animals methylone might be slightly superior to MDMA as a reinforcer. So it isn’t impossible that some methodological issues might uncover a larger methylone/MDMA difference.

 

Relevant Literature
Aarde SM, Huang PK, Creehan KM, Dickerson TJ, Taffe MA. The novel recreational drug 3,4-methylenedioxypyrovalerone (MDPV) is a potent psychomotor stimulant: self-administration and locomotor activity in rats. Neuropharmacology. 2013 Aug;71:130-40. doi: 10.1016/j.neuropharm.2013.04.003. Epub 2013 Apr 15. [PMC (free) Link]

Aarde SM, Angrish D, Barlow DJ, Wright MJ Jr, Vandewater SA, Creehan KM, Houseknecht KL, Dickerson TJ, Taffe MA. Mephedrone (4-methylmethcathinone) supports intravenous self-administration in Sprague-Dawley and Wistar rats. Addict Biol. 2013 Sep;18(5):786-99. doi: 10.1111/adb.12038. Epub 2013 Jan 30.[PMC (free) Link]

Clayton JA, Collins FS (2014) Policy: NIH to balance sex in cell and animal studies. Nature 509: 282-3

Hadlock GC, Webb KM, McFadden LM, Chu PW, Ellis JD, Allen SC, Andrenyak DM, Vieira-Brock PL, German CL, Conrad KM, Hoonakker AJ, Gibb JW, Wilkins DG, Hanson GR, & Fleckenstein AE (2011). 4-Methylmethcathinone (mephedrone): neuropharmacological effects of a designer stimulant of abuse. The Journal of pharmacology and experimental therapeutics, 339 (2), 530-6 PMID: 21810934

Motbey CP1, Clemens KJ, Apetz N, Winstock AR, Ramsey J, Li KM, Wyatt N, Callaghan PD, Bowen MT, Cornish JL, McGregor IS.High levels of intravenous mephedrone (4-methylmethcathinone) self-administration in rats: neural consequences and comparison with methamphetamine.J Psychopharmacol. 2013 Sep;27(9):823-36. doi: 10.1177/0269881113490325. Epub 2013 Jun 5.

Roth ME, Carroll ME (2004a) Sex differences in the acquisition of IV methamphetamine self-administration and subsequent maintenance under a progressive ratio schedule in rats. Psychopharmacology 172: 443-449

Roth ME, Carroll ME (2004b) Sex differences in the escalation of intravenous cocaine intake following long- or short-access to cocaine self-administration. Pharmacol Biochem Behav 78: 199-207

Watterson LR, Hood L, Sewalia K, Tomek SE, Yahn S, Johnson CT, Wegner S, Blough BE, Marusich JA, Olive MF (2012) The Reinforcing and Rewarding Effects of Methylone, a Synthetic Cathinone Commonly Found in “Bath Salts”. J Addict Res Ther S9:002: 1-8

June 13, 2014

Fatal Brain Hyperthermia Induced by MDMA

Filed under: MDMA — mtaffe @ 11:07 am

There is a new paper out at Journal of Neuroscience that addresses physiological mechanisms by which 3,4-methylenedioxymethamphetamine, otherwise known as MDMA or Ecstasy (and more recently Molly), kills people. This is a preclinical study by a group of investigators who work in the Intramural Research Program of the National Institute on Drug Abuse.

Eugene A. Kiyatkin, Albert H. Kim,Ken T. Wakabayashi,Michael H. Baumann, and Yavin Shaham. Critical Role of Peripheral Vasoconstriction in Fatal Brain Hyperthermia Induced by MDMA (Ecstasy) under Conditions That Mimic Human Drug Use, J Neurosci. 2014 Jun 4;34(23):7754-62. doi: 10.1523/JNEUROSCI.0506-14.2014.[PubMed; JNeuro]

The first author, Kiyatkin, has a neat little preparation for the simultaneous monitoring of body temperature in brain, muscle and skin. He has been working away over the years reporting brain/peripheral differentials in the temperature response to drugs, including MDMA.

Mean (±SEM) changes in NAc, muscle, and skin temperatures induced by injection of 9 mg/kg MDMA (C). Mean (±SEM) MDMA-induced changes in temperature relative to saline injection (G), temperature differentials (K), and locomotion (O).

from Fig 1: Mean (±SEM) changes in NAc, muscle, and skin temperatures induced by injection of 9 mg/kg MDMA (C). Mean (±SEM) MDMA-induced changes in temperature relative to saline injection (G), temperature differentials (K), and locomotion (O).

This new paper first shows that brain (probes inserted into the nucleus accumbens) temperature; muscle temperature; skin temperature and that MDMA (1, 3, 9 mg/kg, s.c.) induces a dose-related increase in brain and muscle temperature in Long-Evans rats (the sex wasn’t specified in the methods, one brief mention of males in the Abstract) under 22.5 °Celsius ambient temperature conditions. See the excerpt from Fig 1 as a visual reference. The brain/muscle temperature differential (~1 °C) didn’t change across time after MDMA but of course since skin temperature didn’t increase, the brain/skin differential (~2.5 °C at baseline) became larger. So far so good, but Kiyatkin has shown similar effects before. Also, the demonstration that experimental animals’ temperature goes up after MDMA is hardly novel. It occurs in mouse, rat, guinea pig, swine, monkey and quietly resting humans.

The next major point of this paper is that under warmer (29 °C) ambient temperature conditions, all of the animals (6/6) died after the 9 mg/kg dose. Now, it is true that most laboratory papers on the thermoregulatory response to MDMA do not emphasize the lethality rate. But many of them do report it. Malberg and Seiden, 1998 and Gordon et al, 1991 are cases in point. Those studies featured relatively high MDMA doses, true, but they were doses that were not lethal at lower ambient temperature conditions. Gilpin and colleagues (2011) reported ~30% mortality at normal ambient temperature after a 10 mg/kg dose (i.e., closer to the 9 mg/kg used in Kiyatkin et al) when animals were provided access to a running wheel, possibly addressing an issue of excess heat generation, rather than heat dissipation, but the concept is related. Finally, Brown and Kiyatkin showed 9 mg/kg MDMA under high ambient temperature leads to lethality in a 2004 paper. There are other mentions in the literature that make it very clear that rodents are at increased risk of an unregulated hypothermia and death under high ambient temperature conditions, given an identical dose of MDMA.

There is one important procedural note at this point in the story. A single group of 12 animals participated in all of the studies. The original challenges of 1, 3 and 9 mg/kg were conducted on three sequential days. Subsequent experiments involved another 9 mg/kg dose under normal ambient (in the context of a cage mate) and then the final lethal experiment. The paper doesn’t appear to specify the testing order beyond this and yet the listed subject numbers of 12 for saline, 11 for 9 mg/kg, 9 for 1 mg/kg and 7 for 3 mg/kg implies perhaps that was the test order. If doses were mixed order then the N in each condition doesn’t make any sense at all. Either way, the subject drop-out is nowhere explained that I can locate. The final two experiments were down to N=6. One has to assume that they had some subject mortality after MDMA dosing (but not saline) even under lower ambient temperature. The design also raises a question about the effects of repeated intermittent dosing on the animals that survived until the last experiment. This is probably a good feature in making this model consistent with the human user, but really complicates things in terms of knowing whether the present results were a result of the conditions or of the prior history of the animals.

The second, social interaction experiment is strange in design. It featured the introduction of a new male rat into the experimental animal’s home cage which might be viewed in the light of an Resident-Intruder paradigm, generally used as a stressor. This lacks the setup of including a female with the original male but the point is that “social” conditions need a good deal of explication. This is lacking in the present paper. Acclimated social groups will huddle together under some conditions- this is clearly of great interest when the study concerns body heat – but we are uncertain if that happened here. Certainly an examination of the temperature curves under saline conditions with and without the “social” interaction do not suggest any huddling or even any interaction after the first hour of acclimation. It is even more pertinent to describe the mode when the implicit translational goal is to model humans using ecstasy. Do humans “huddle”? Do humans interact like the animals in the Kiyatkin model do? This is not addressed. Interestingly, Brown and Kiyatkin already showed hyperthermia after 9 mg/kg MDMA is increased by social interaction with a female rat in their 2004 paper. Of greater interest to the point Kiyatkin and colleagues appear to be pursuing with this manipulation, Fantegrossi and colleagues (2003) showed that mice who are socially acclimated in housing groups of 6 or 12 are at increased risk of mortality (versus single housing) across a range of MDMA doses (and isomers).

I am not entirely sure why*, but the paper essentially ignores any discussion (and in some cases citation) of prior work that is highly relevant to the central claims of the paper. When prior related work is cited, it is mentioned in a way that minimizes the direct applicability to the present study. Dafters identifed the relationship between the temperature response to MDMA and the ambient temperature under which rats were examined in 1994 and 1995. Malberg and Seiden (1998; Journal of Neuroscience, no less) used radiotelemetry and an exacting range of ambient temperature conditions to show this relationship in unrestrained, freely moving animals. The ambient temperature/body temperature relationship may be a bit more uncertain in human and non-human primates, this would appear central to the discussion but is not really addressed. Blessing and colleagues showed that peripheral vasoconstriction following MDMA contributes to the increase in body temperature in rabbit and rat (also in J. Neuroscience) models.

As a final point, this paper makes a huge deal out of the role of vasoconstriction as an explanatory mechanism. As mentioned above, Blessing and colleagues already demonstrated this in the context of hyperthermia, if not lethality. Still, I expected that this paper would have directly either measured or manipulated vasoconstriction. The experiments did not. Instead, “vasoconstriction” is merely inferred from the muscle/skin temperature differential. This is disappointing.

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*Given the realities of publishing in the Journal of Neuroscience, one presumes the authors were highly motivated to write this paper in a way that claimed novelty. Proper reference to, and discussion of, the relevant literature as per this blog post would have undoubtedly undercut an impression of novelty.

Disclaimer: I work on this topic and am also professionally acquainted with two of the authors. These may constitute conflicts of interest.

September 17, 2013

Bathsalts involved in 22,904 Emergency Department Visits in the US in 2011

Filed under: 4-MMC/Mephedrone, Cathinones, MDMA, Methylone — mtaffe @ 12:09 pm

Newly released data from the Drug Abuse Warning Network under SAMHSA, detail Emergency Department visits that involved bathsalts in 2011 [PDF].

Samhsa-ER-bathsaltsSep2013Unfortunately I can’t find any definition of the terms so I don’t know if any specific drugs had to be confirmed in body tissues or not. Nor do I know what they lumped under this catchall street-name for their data collecting and analysis. At the very least we have to presume there is some diversity here in terms of the actual drug being used. Mephedrone, methylone and MDPV have to be the suspects based on apparent presence in the US but since medical emergency is presumably rare, it may be that these visits disproportionally represent some other drug. Presumably in the cathinone class…but perhaps not.

One thing that would be of interest, but not something that appears in this dataset, would be a review of symptoms. The presence of “bath salts” with other drug combinations can be interpreted several ways. For example, it could suggest that bathsalts are more of a problem in the presence of other drugs…but symptom discrimination could help. Lethal or near-lethal alcohol and stimulant profiles look very different so if you have an alcohol+bathsalts case that looks like stimulant overdose, the presumption has to be that the alcohol had little to do with it.

In other recent news, three “molly” related deaths over the recent months have been confirmed as involving methylone, MDMA and methylone with MDMA, respectively.

September 4, 2013

Assessing “Molly”

Filed under: Cathinones, MDMA, Methylone — mtaffe @ 9:57 am

I just got off the phone with a producer of a public radio program that wanted to do a small bit on “molly” tomorrow. With luck I’ll be on around 10:40 Eastern. The conversation, however, dipped heavily into the fact that when the media reports that a user might have taken “molly” we really do not know what drug has been experience.

So I turned to ecstasydata.org and searched for “molly” which generally turned up things with this in the Tablet Name field. I’ll assume this is a good enough proxy for the drug entity in question as having been marketed, or represented to the user, as “Molly”.

There were 80 entries listed from 4/1/2000 to 8/20/2013. One from 2000 (which contained DXM), one from 2007, two each from 2008 and 2009, 6 from 2010, 17 from 2011, 33 from 2012 and 17 from 2013 up to this point in the year.

I did a quick scan and headcount of the active substances identified. Forty one of them contained MDMA, by far the plurality. There were 12 that contained methylone (aka bk-MDMA, the cathinone cousin of MDMA) and 7 that contained methamphetamine. Many of the MDMA ones came in combination with other compounds including caffeine and methamphetamine. There was the usual (for the tablets-represented-as-Ecstasy) smattering of other suspects such as PMMA, BZP, MDA. Additional cathinones also appeared, such as ethylone, 4-MEC and ethcathinone.

The first appearance of a cathinone was methylone in a sample analyzed in October of 2011. Six of the samples analyzed in 2013 are methylone (only) and two more were single-compound cathinones (ethylone, 4-MEC).

These data can only reflect what has been submitted to the harm reduction organization by users. It is certainly the case that there is a selection bias and so viewing this as representative of the whole drug market is a problem. It appears likely that users would submit samples that seem suspicious to them preferentially. This may increase the appearance of substitutions and combinations over the pure MDMA that users are seeking as Molly. There is the obvious bias for samples from users that even know about ecstasydata.org and are motivated enough to submit a sample…one might read this as a slightly more educated/interested/devoted population of users. And it is impossible to determine relative marketshare of the drug samples that are submitted- it may reflect a large supply available in a given region or a more exclusive supply that an isolated user population has access to.

In a word, there are caveats.

Nevertheless, over the years the Ecstasydata.org information on drug preparations represented as Ecstasy has accorded very well with the data from things analyzed from law enforcement seizure and from other countries. Consequently this enhances confidence that these initial results are giving us a general picture of the psychoactive drug content of items being sold as Molly.

July 9, 2012

Mephedrone decreases body temperature, fails to generate hyperthermia at high ambient temperature

Filed under: 4-MMC/Mephedrone, Cathinones, MDMA, Methamphetamine — mtaffe @ 11:29 am

The following has been accepted for publication:

Miller, M.L., Creehan, K.M., Angrish, D., Barlow, D.J., Houseknecht, K.L., Dickerson, T.J. and Taffe, M.A. Changes in ambient temperature differentially alter the thermoregulatory, cardiac and locomotor stimulant effects of 4-methylmethcathinone (mephedrone), Drug Alcohol Depend, 2013 Jan 1;127(1-3):248-53. doi: 10.1016/j.drugalcdep.2012.07.003. Epub 2012 Jul 23.[PubMed]

In this study, rats were monitored for changes in body temperature, home cage ambulatory activity and heart rate after the administration of 4-methylmethcathinone (4-MMC or mephedrone). The study was conducted at low (20°C) and high (30°C) ambient temperature because prior work has shown that 3,4-methylenedioxymethamphetamine (MDMA) produces hypothermia at low ambient and hyperthermia at high ambient temperature in rats (Malberg and Seiden, 1998; Dafters et al, 1994). As discussed in a prior post on the neuropharmacology of 4-MMC, and our recent study (Huang et al, 2012) on the effects of 4-MMC, MDMA and methamphetamine on wheel activity [ blogpost ], there is reason to believe the effects of this cathinone would be similar to those of MDMA.

The main finding was that 4-MMC (1.0-5.6 mg/kg, s.c.) caused a dose-dependent decrease in body temperature under 20°C ambient conditions but no alteration at the higher ambient temperature. A followup experiment showed that 5.6 mg/kg MDMA, s.c., increased body temperature, similar to findings in prior studies. Therefore, it appears that the risk for hyperthermia is attenuated for 4-MMC compared with MDMA. Locomotor activity in the home cage was dose-dependently increased by 4-MMC with greater stimulation at the higher ambient temperature condition. The maximum locomotor increase under 30°C ambient conditions was less than that produced by 5.6 mg/kg MDMA and similar to that produced by 1.0 mg/kg methamphetamine. Effects of 4-MMC on heart rate were modest with a reduction relative to vehicle observed in the low ambient temperature condition only.

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