Effects of N6-cyclohexyl adenosine (CHA) on isolation-induced aggression in male mice

Several studies have suggested adenosine receptor involvement in the modulation of aggressive behavior; however, the influence of adenosine A1 agonists on aggression is scarcely known. In this study, we examined the effect of N6-cyclohexyl adenosine (CHA; 0.025-0.4 i.p.), a selective adenosine A1 receptor agonist, on agonistic behavior elicited by isolation in male mice. Individually housed mice were exposed to anosmic standard opponents 60 min after drug administration, and the encounters were videotaped and evaluated using an ethologically based analysis. CHA exhibited an ethopharmacological profile characterized by a selective decrease of offensive behaviors (threat and attack) at the intermediate dose (0.1 mg/kg), without impairment of motor activity. In contrast, the antiaggressive action of the highest doses used (0.2 and 0.4 mg/kg) was accompanied by a marked increase of immobility. It is concluded that the behavioral effects observed in this study could be related to an adenosine modulatory action on other neurotransmitter systems (dopamine/serotonin).