Temporal effects of castration on emotionality and shock-induced aggression in adult male rats.

Alterations in shock-induced aggressive behavior, general emotional reactivity and flinch thresholds in 61 and 82 day old male rats were analyzed at either 3 or 6 weeks following castration. Castrated animals were significantly less aggressive than sham-operated controls at the 6 week but not the 3 week interval. These findings could not be attributed to changes in flinch threshold as neither treatment nor time affected this measure. With regard to emotionality, castrated animals were significantly more reactive than the control animals at the 3 week but not 6 week interval. The data are interpreted as indicating that castration altered shock-induced aggression by preventing a maturational increase in such behavior. These behavioral alterations are compared to previously reported time-dependent changes in brain monoaminergic dynamics following gonadectomy. The conclusions support the concept of a necessary balance between catecholaminergic and serotonergic systems with regard to affective behavior.