TL neuro

March 28, 2013

Cannabidiol attenuates memory deficits that are caused by Δ9-tetrahydrocannabinol

Filed under: Cannabidiol, Cannabis, CANTAB, vsPAL — mtaffe @ 1:30 pm

A prior post discussed an apparently protective effect of cannabidiol (CBD) against memory deficits in humans caused by smoking cannabis. The key feature of the design was that Morgan and colleagues examined the Δ9-tetrahydrocannabinol (THC) and CBD content of their subjects’ (self-provided cannabis). The authors then grouped subjects into those who had relatively high-CBD cannabis and relatively poor-CBD cannabis; THC content was roughly equivalent. The authors reported that delayed recall was impaired acutely by cannabis smoking…but only if the cannabis was low in CBD. The relatively higher CBD content cannabis did not impair the memory performance of those individuals who smoked it.

The major concern with the study is that the humans subjects self-selected themselves into the treatment groups. Higher-CBD cannabis is relatively rare in recreational markets. It is possible that cannabis users who have access to (or intentionally choose) this restricted sub-population of the available cannabis are different, in one or more ways, than those users who do not have access or prefer other types of cannabis. Since they obtained their own cannabis we cannot know if there were other factors, socio-economic, regional, use-profile, peer groups, etc that were associated with choosing one type of cannabis over another. We similarly cannot know if they differed in memory ability and indeed there was a nonsignificant trend for better baseline memory in the CBD-enriched cannabis subjects.

We therefore conducted a controlled animal study in which the effects of CBD on a memory-impairing dose of THC could be assessed in the same subjects. This paper has recently been accepted for publication published.

Wright, M.J., Jr., Vandewater, S.A. and Taffe, M.A. Cannabidiol attenuates deficits of visuo-spatial associative memory induced by Δ9-tetrahydrocannabinol, Brit J Pharmacol, 2013 Dec;170(7):1365-73 [ PubMed ][ Publisher Link ]

PALFig-3stimGreyIn this task the animal first sees a given pattern in a single spatial location on the screen (“sample” phase of the trial). After touching it, there is a brief screen blank and then the pattern is presented in two or more positions (“choice” phase). Touching the pattern in the same location is a correct response. The difficulty of each trial is increased by presenting 2, 3 or 4 stimulus-location associations first and then querying all of them- in this case a successful trial completion requires touching the correct location for each stimulus that was presented. We’ve previously shown that THC degrades performance of this task in a manner that depends on both the trial difficulty (how many pattern-location associations have to be remembered) as well as the THC dose. This is interpreted as a relatively selective effect- in contrast a spatial memory task which does not depend on associating any pattern with the spatial location is impaired in a difficulty-independent manner.

CBD-THC-vsPALIn this figure we show the effect of multiple treatment conditions on the performance of the most difficult trials in which 4 stimulus-location associations have to be completed correctly. In this case, the animals are permitted up to 6 attempts to get each trial right. The data show that both 0.2 and 0.5 mg/kg doses of THC reduce the proportion of correctly completed trials. This effect is ameliorated if the THC is injected simultaneously with 0.5 mg/kg CBD. Since it was the same subjects, tested repeatedly, the effects of pre-existing differences in memory function can be ruled out.

Update:

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These studies were supported in part by P20 DA024194.

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1 Comment »

  1. […] The investigation found no evidence that cannabidiol can ameliorate the thermoregulatory or hypolocomotor effects of THC when administered either simultaneously (as in Figure 1, below) or prior to THC. Increasing the ratio of CBD:THC from 1:1 to 3:1 had no differential effect. Thus we find no protective effect of CBD against these particular endpoints in the rat. This contrasts with our recent finding that CBD can be protective against memory-impairing effects of THC in the monkey (PubMed, blogpost). […]

    Pingback by Cannabidiol fails to attenuate THC-induced hypothermia | TL neuro — November 23, 2014 @ 11:38 am


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