text: ICI118,551 HCl (1.25-5 mg/kg, IP), a selective beta 2-adrenoceptor antagonist, also blocked the desipramine-induced enhancement of aggressive behavior in a dose-dependent manner, whereas << metoprolol tartrate >> (5-20 mg/kg, IP), a selective [[ beta 1-adrenoceptor ]] antagonist, did not affect it.