A Cannabinoid CB 1 Receptor-Positive Allosteric Modulator Reduces Neuropathic Pain in the Mouse with No Psychoactive Effects

Abstract

The CB 1 receptor represents a promising target for the treatment of several disorders including pain-related disease states. However, therapeutic applications of Δ 9-tetrahydrocannabinol and other CB 1 orthosteric receptor agonists remain limited because of psychoactive side effects. Positive allosteric modulators (PAMs) offer an alternative approach to enhance CB 1 receptor function for therapeutic gain with the promise of reduced side effects. Here we describe the development of the novel synthetic CB 1 PAM, 6-methyl-3-(2-nitro-1-(thiophen-2-yl)ethyl)-2-phenyl-1H-indole (ZCZ011), which augments the in vitro and in vivo pharmacological actions of the CB 1 orthosteric agonists CP55,940 and N-arachidonoylethanolamine (AEA). ZCZ011 potentiated binding of 3 HCP55,940 to the CB 1 receptor as well as enhancing AEA-stimulated 35 SGTPγS binding in mouse brain membranes and β-arrestin recruitment and ERK phosphorylation in hCB 1 cells. In the whole animal, ZCZ011 is brain penetrant, increased the potency of these orthosteric agonists in mouse behavioral assays indicative of cannabimimetic activity, including antinociception, hypothermia, catalepsy, locomotor activity, and in the drug discrimination paradigm. Administration of ZCZ011 alone was devoid of activity in these assays and did not produce a conditioned place preference or aversion, but elicited CB 1 receptor-mediated antinociceptive effects in the chronic constriction nerve injury model of neuropathic pain and carrageenan model of inflammatory pain. These data suggest that ZCZ011 acts as a CB 1 PAM and provide the first proof of principle that CB 1 PAMs offer a promising strategy to treat neuropathic and inflammatory pain with minimal or no cannabimimetic side effects.