Spontaneous and Naloxone-Precipitated Withdrawal Behaviors From Chronic Opiates are Accompanied by Changes in N-Oleoylglycine and N-Oleoylalanine Levels in the Brain and Ameliorated by Treatment With These Mediators.

Rationale: The endocannabinoidome mediators, N-Oleoylglycine (OlGly) and N-Oleoylalanine (OlAla), have been shown to reduce acute naloxone-precipitated morphine withdrawal affective and somatic responses. Objectives: To determine the role and mechanism of action of OlGly and OlAla in withdrawal responses from chronic exposure to opiates in male Sprague-Dawley rats. Methods: Opiate withdrawal was produced: 1) spontaneously 24 h following chronic exposure to escalating doses of morphine over 14 days (Experiments 1 and 2) and steady-state exposure to heroin by minipumps for 12 days (Experiment 3), 2) by naloxone injection during steady-state heroin exposure (Experiment 4), 3) by naloxone injection during operant heroin self-administration (Experiment 5). Results: In Experiment 1, spontaneous morphine withdrawal produced somatic withdrawal reactions. The behavioral withdrawal reactions were accompanied by suppressed endogenous levels of OlGly in the nucleus accumbens, amygdala, and prefrontal cortex, N-Arachidonylglycerol and OlAla in the amygdala, 2-arachidonoylglycerol in the nucleus accumbens, amygdala and interoceptive insular cortex, and by changes in colonic microbiota composition. In Experiment 2, treatment with OlAla, but not OlGly, reduced spontaneous morphine withdrawal responses. In Experiment 3, OlAla attenuated spontaneous steady-state heroin withdrawal responses at both 5 and 20 mg/kg; OlGly only reduced withdrawal responses at the higher dose of 20 mg/kg. Experiment 4 demonstrated that naloxone-precipitated heroin withdrawal from steady-state exposure to heroin (7 mg/kg/day for 12 days) is accompanied by tissue-specific changes in brain or gut endocannabinoidome mediator, including OlGly and OlAla, levels and colonic microbiota composition, and that OlAla (5 mg/kg) attenuated behavioural withdrawal reactions, while also reversing some of the changes in brain and gut endocannabinoidome and gut microbiota induced by naloxone. Experiment 5 demonstrated that although OlAla (5 mg/kg) did not interfere with operant heroin self-administration on its own, it blocked naloxone-precipitated elevation of heroin self-administration behavior. Conclusion: These results suggest that OlAla and OlGly are two endogenous mediators whose brain concentrations respond to chronic opiate treatment and withdrawal concomitantly with changes in colon microbiota composition, and that OlAla may be more effective than OlGly in suppressing chronic opiate withdrawal responses.

Oleoyl alanine (HU595): a stable monomethylated oleoyl glycine interferes with acute naloxone precipitated morphine withdrawal in male rats.

RATIONALE: Oleoyl glycine, a little studied fatty acid amide similar in structure to anandamide, interferes with nicotine addiction in mice and acute naloxone-precipitated morphine withdrawal (MWD) in rats. Because endogenous oleoyl glycine is subject to rapid enzymatic deactivation, we evaluated the potential of more stable analogs to interfere with opiate withdrawal. OBJECTIVES: The potential of monomethylated oleoyl glycine (oleoyl alanine, HU595) to interfere with somatic and aversive effects of acute naloxone-precipitated MWD, its duration, and mechanism of action was assessed in male Sprague Dawley rats. The potential of dimethylated oleoyl glycine (HU596) to interfere with the aversive effects of naloxone-precipitated MWD was also investigated. RESULTS: Oleoyl alanine (HU595) interfered with somatic and aversive effects produced by naloxone-precipitated MWD at equivalent doses (1 and 5 mg/kg, i.p.) as we have reported for oleoyl glycine; however, oleoyl alanine produced a longer lasting (60 min) interference, yet did not produce rewarding or aversive effects on its own and did not modify locomotor activity. HU596 was not effective. The interference with aversive effects of naloxone-precipitated MWD by oleoyl alanine was prevented by both a PPARα antagonist and a CB1 receptor antagonist. Accordingly, the compound was found to inhibit FAAH and activate PPARα in vitro. Finally, oleoyl alanine also reduced acute naloxone-precipitated MWD anhedonia, as measured by decreased saccharin preference. CONCLUSIONS: Oleoyl alanine (also an endogenous fatty acid) may be a more stable and effective treatment for opiate withdrawal than oleoyl glycine.