Recovery of hyperreactivity in rats with simultaneous septal and subcortical lesions

Rats with lesions of the forebrain septal area, simultaneously combined with lesions of one of several subcortical or cortical sites within the cerebrocortical system were rated for behavioral reactivity to probing stimulation, capture and handling. All of the cerebrocortical system lesions prevented recovery of septal hyperreactivity over a 21-day postoperative recovery interval in the combined lesion groups. Once ratings of reactivity recommenced, all of the combined lesion groups, with the possible exception of the combined lateral geniculate body-septal group, declined in reactivity more rapidly than a group of rats with septal lesions alone tested beginning 2 days after surgery. Rats with septal or cerebrocortical lesions alone were not hyperreactive at the end of the 21-day recovery interval. Mechanisms involving lesion-induced changes in monoaminergic activity are favored over neuroanatomical explanations in accounting for the recovery of function phenomena observed in the experiment.