Blockade of Endocannabinoid Hydrolytic Enzymes Attenuates Precipitated Opioid Withdrawal Symptoms in Mice

Abstract

⌬9 -Tetrahydrocannbinol (THC), the primary active constituent of Cannabis sativa, has long been known to reduce opioid withdrawal symptoms. Although THC produces most of its pharmacological actions through the activation of CB 1 and CB 2 cannabinoid receptors, the role these receptors play in reducing the variety of opioid withdrawal symptoms remains unknown. The endogenous cannabinoids, N-arachidonoylethanolamine (anandamide; AEA) and 2-arachidonylglycerol (2-AG), activate both cannabinoid receptors but are rapidly metabolized by fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), respectively. The objective of this study was to test whether increasing AEA or 2-AG, via inhibition of their respective hydrolytic enzymes, reduces naloxone-precipitated morphine withdrawal symptoms in in vivo and in vitro models of opioid dependence. Morphine-dependent mice challenged with naloxone reliably displayed a profound withdrawal syndrome, consisting of jumping, paw tremors, diarrhea, and weight loss. THC and the MAGL inhibitor 4-nitrophe-]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate (JZL184) dose dependently reduced the intensity of most measures through the activation of CB 1 receptors. JZL184 also attenuated spontaneous withdrawal signs in morphine-dependent mice. The FAAH inhibitor N-(pyridin-3-yl)-4-(3-(5-(trifluoromethyl)pyridin-2-yloxy)benzyl)-piperdine-1-carboxamide (PF-3845) reduced the intensity of naloxoneprecipitated jumps and paw flutters through the activation of CB 1 receptors but did not ameliorate incidence of diarrhea or weight loss. In the final series of experiments, we investigated whether JZL184 or PF-3845 would attenuate naloxoneprecipitated contractions in morphine-dependent ilea. Both enzyme inhibitors attenuated the intensity of naloxoneinduced contractions, although this model does not account mechanistically for the autonomic withdrawal responses (i.e., diarrhea) observed in vivo. These results indicate that endocannabinoid catabolic enzymes are promising targets to treat opioid dependence.

Elevating endocannabinoid levels: pharmacological strategies and potential therapeutic applications

“…Moreover, when it was administered repeatedly to mice, this MAG lipase inhibitor was found to produce physical dependence, as indicated by SR141716A-precipitated paw fluttering, and to cause tolerance to develop both to its own antinociceptive effect, unless it was administered at a low antinociceptive dose, and to that of the direct CB 1 /CB 2 receptor agonists, Δ 9 -tetrahydrocannabinol and R-(+)-WIN55212 (56,73) . In line with some of these observations is the finding that both JZL184 and the direct CB 1 /CB 2 receptor partial agonist, Δ 9 -tetrahydrocannabinol, could reduce four naloxone precipitated physical withdrawal signs in morphine-dependent mice (41) . In contrast, only two of these withdrawal signs could be attenuated by the FAAH inhibitor, PF3845.…”

The Selective Monoacylglycerol Lipase Inhibitor MJN110 Produces Opioid-Sparing Effects in a Mouse Neuropathic Pain Model

“…Spinal cords and brains were rapidly harvested, snap-frozen in dry ice, and stored at 280°C until the time of processing. Tissues were further processed according to methods described previously (Ramesh et al, 2011;Ignatowska-Jankowska et al, 2014). See the (Supplemental Material for details.…”

Chemical Probes of Endocannabinoid Metabolism

“…Opioid Withdrawal. THC is known to reduce the severity of opioid withdrawal in humans and rodents, and recently endocannabinoid hydrolase inhibitors were also found to alleviate symptoms of precipitated and spontaneous withdrawal in opioid-dependent mice (Ramesh et al, 2011). Treatment of morphinedependent mice with the mu opioid receptor antagonist nalaxone induces a profound withdrawal phenotype consisting of jumping, paw tremors, diarrhea, and weight loss.…”

“…However, several studies have reported that lower doses of JZL184 that partially inhibit brain MAGL and cause submaximal elevations in brain 2-AG (Long et al, 2009b) retain efficacy in rodent models of pain (Busquets-Garcia et al, 2011;Ghosh et al, 2012), anxiety (Busquets-Garcia et al, 2011;Kinsey et al, 2011;Sciolino et al, 2011), emesis (Sticht et al, 2011), and opioid withdrawal (Ramesh et al, 2011). Importantly, the antinociceptive and anxiolytic-like effects elicited by a low dose of JZL184 (8 mg/kg i.p.)…”