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.