Can THC Protect the Brain against Methamphetamine's Toxicity?

A fascinating new study in the journal Neuropharmacology, suggests the brain's endocannabinoid system can be aided in its neuroprotective efforts against the toxicity of methamphetamine by introducing external cannabinoids to increase the system's "endogenous tone". The cannabinoids in question, THC, URB and JZL, appear to inhibit the breakdown of the brain's own endocannabinoids, improving the ability of the brain to protect itself against the "external insult" of overdoses of methamphetamine.

Here is the abstract, via ScienceDirect:

Abstract

Methamphetamine toxicity is associated with cell death and loss of dopamine neuron terminals in the striatum similar to what is found in some neurodegenerative diseases. Conversely, the endocannabinoid system (ECS) has been suggested to be neuroprotective in the brain, and new pharmacological tools have been developed to increase their endogenous tone. In this study, we evaluated whether ECS stimulation could reduce the neurotoxicity of high doses of methamphetamine on the dopamine system. We found that methamphetamine alters the levels of the major endocannabinoids, anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) in the striatum, suggesting that the ECS participates in the brain responses to methamphetamine. Δ⁹-tetrahydrocannabinol (THC), a cannabis-derived agonist of both CB₁ and CB₂cannabinoid receptors, or inhibitors of the main enzymes responsible for the degradation of AEA and 2-AG (URB597 and JZL184, respectively), blunted the decrease in striatal protein levels of tyrosine hydroxylase induced by methamphetamine. In addition, antagonists of CB₂, but not of CB₁, blocked the preventive effects of URB597 and JZL184, suggesting that only the former receptor subtype is engaged in neuroprotection exerted by ECS stimulation. Finally, we found that methamphetamine increases striatal levels of the cytokine tumor necrosis factor alpha, an effect that was blocked by ECS stimulation. Altogether, our results indicate that stimulation of ECS prior to the administration of an overdose of methamphetamine considerably reduces the neurotoxicity of the drug through CB₂ receptor activation and highlight a protective function for the ECS against the toxicity induced by drugs and other external insults to the brain.

And here is a table showing levels of two of the major endocannabinoids, AEA and 2-AG,  following doses of methamphetamine:

And finally striatal levels of the cytokine tumor necrosis factor alpha:

Source:
http://www.sciencedirect.com/science/article/pii/S0028390814001099