Methylxanthine-facilitated shock-induced aggression in the rat.

The methylxanthines caffeine and aminophylline, in daily doses of 100 mg/kg, facilitated shock-induced aggression in the rat. Under the limited parameters of this study, there was no induction of mouse-killing behavior or alteration of jump thresholds. Additional studies showed the optimal dose and time course for the facilitation of shock-induced aggression by caffeine to be 50 mg/kg administered i.p. 4 h prior to testing. Facilitation of a central adrenergic system may be the mechanism of action.