Synthetic cannabinoids versus delta-9-tetrahydrocannabinol: abuse-related consequences of enhanced efficacy at the cannabinoid 1 receptor

Author

Travis Grim, Virginia Commonwealth UniversityFollow

DOI

https://doi.org/10.25772/F948-2Z19

Defense Date

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Pharmacology & Toxicology

First Advisor

Aron Lichtman

Abstract

In the past ten years, synthetic cannabinoids (SC) have emerged as drugs of abuse. Unlike D⁹-tetrahydrocannabinol (THC), many SCs are associated with serious health complications and death. One way in which THC and SCs differ lies with their enhanced potency and efficacy at the CB₁ receptor. No current methods exist to measure efficacy at the CB₁ receptor in vivo, and the abuse-related properties of SC cannabinoids are not well explored. Here, we utilized CB₁ wild type (WT), heterozygous (HET), and knockout (KO) mice. By employing CB₁ ligands which differ in efficacy we have developed a method to explore the relationship between efficacy and the ability to produce cannabimimetic (catalepsy, hypothermia, and antinociception) effects when CB₁ expression was reduced by half. Additionally, the intracranial self-stimulation procedure (ICSS) was utilized to investigate the effects of enhanced efficacy at CB₁ upon reward processes using representative SC CP55,940. As predicted, the potency shift between WT and HET mice inversely correlated with the efficacy of the test drug for both hypothermia and antinociception, but not catalepsy. This efficacy stratification was correlated with the agonist-stimulated [³⁵S]GTPgS binding assay, demonstrating this model as an effective tool to ascertain in vivo efficacy differences at CB₁. In ICSS, CP55,940 elicited only rate-decreasing effects acutely, although tolerance developed following repeated dosing, with no evidence for spontaneous or rimonabant-precipitated withdrawal. Together, these data indicate that highly efficacious cannabinoid ligands require few receptors to produce cannabimimetic effects, and that the model provides an effective means to quickly ascertain differences in efficacy.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

12-9-2015