β-Arrestin 2 dependence of δ opioid receptor agonists is correlated with alcohol intake

Background and Purpose Opioid receptor agonists are being developed as potential treatments for depression and alcohol use disorders. This is particularly interesting as depression is frequently co-morbid with alcohol use disorders. Yet we have previously shown that receptor agonists range widely in their ability to modulate alcohol intake; certain receptor agonists actually increase alcohol consumption in mice. We propose that variations in -arrestin 2 recruitment contribute to the differential behavioural profile of receptor agonists. Experimental ApproachWe used three diarylmethylpiperazine-based non-peptidic receptor selective agonists (SNC80, SNC162 and ARM390) and three structurally diverse receptor agonists (TAN-67, KNT127 and NIH11082). We tested these agonists in cAMP and -arrestin 2 recruitment assays and a behavioural assay of alcohol intake in male C57BL/6 mice. We used -arrestin 2 knockout mice and a model of depression-like behaviour to further study the role of -arrestin 2 in receptor pharmacology. Key ResultsAll six tested receptor agonists were full agonists in the cAMP assay but displayed distinct -arrestin 2 recruitment efficacy. The efficacy of receptor agonists to recruit -arrestin 2 positively correlated with their ability to increase alcohol intake (P < 0.01). The effects of the very efficacious recruiter SNC80 on alcohol intake, alcohol place preference and depression-like behaviour were -arrestin 2-dependent. Conclusions and ImplicationsOur finding that receptor agonists that strongly recruit -arrestin 2 can increase alcohol intake carries important ramifications for drug development of receptor agonists for treatment of alcohol use disorders and depressive disorders. (c) 2015 The British Pharmacological Society