Attenuation of the effects of ethanol on social behavior by alpha₂-adrenoceptor antagonists

In a social behavior test in mice ethanol (2 g/kg) significantly reduces the time spent in social interaction and increases locomotor activity. The relatively selective alpha₂-adrenoceptor antagonists atipamezole and idazoxan alone have no significant effect on either social interaction or locomotor activity in this test. However, when coadministered with 2 g/kg ethanol, atipamezole (0.3-3.0 mg/kg) significantly attenuated the ethanol-induced reduction in the time spent in social interaction without any effect on ethanol's locomotor stimulant action. Idazoxan (0.3-1.0 mg/kg) also showed a trend towards reversing the reduction in the time spent in social interaction although this was accompanied by a significant attenuation of the locomotor stimulant effect of ethanol. The results indicate that alpha₂-adrenoceptors may modulate ethanol's effects on social interaction in mice.