Alpha-2 Adrenergic Agonists Reduce Heavy Alcohol Drinking and Improve Cognitive Performance in Mice.

Abstract

Alcohol use disorder (AUD) is one of the top behavioral causes of global disease burden in the United States. Repeated cycles of alcohol intoxication and abstinence induce neuroplastic alterations which induce excessive drinking and cognitive impairments. A system deeply dysregulated by chronic drinking is norepinephrine (NE). At moderate levels, NE has beneficial effects on cognition and behavior, mediated by the α2 adrenergic receptor (AR) subtype. Whether α2 AR activation blunts alcohol consumption in models of heavy drinking has not been determined, and whether α2 AR activation improves cognitive performance following chronic alcohol consumption is unknown. Here, we show that the α2 AR agonist clonidine worsens ethanol-induced hypothermia and sedation in male mice, while the more selective α2 AR agonist guanfacine is devoid of these effects. We also observed that, in male and female mice, while both clonidine and guanfacine reduce heavy alcohol drinking, guanfacine does so with higher potency. Furthermore, guanfacine improved cognitive performance in a temporal order test and, partially, in a novel object recognition test but had no effect in a novel spatial location test, in male and female ethanol-experienced mice. Finally, we found that chronic intermittent ethanol drinking increases the number of persistently activated NE neurons in both the locus ceruleus and the nucleus of the tractus solitarius, in both male and female mice. Our results highlight a central role for the α2 AR system in heavy alcohol drinking and associated cognitive deficits, suggesting that α2 AR stimulation may represent a viable pharmacological strategy to treat AUD.