Suppression of VMH-lesion-induced reactivity and aggressiveness in the rat by stimulation of lateral septum, but not medial septum or cingulate cortex.

Animals made vicious with bilateral ventromedial hypothalamic lesions had bipolar electrodes implanted unilaterally in the lateral septum, medial septum, or cingulate cortex. Four days later, the animals' reactivity and aggressiveness were evaluated 5 min before, during, and 5 min after stimulation at 20 micronA (60 Hz, sine wave). Lateral septal stimulation suppressed reactivity and aggressiveness by almost 80% compared with pre- and poststimulation levels. Stimulation of neither the cingulate cortex nor the medial septum produced a change reliably different from that seen in unstimulated control animals. Further tests with stimulation of the lateral septum at the 20-micronA level showed that neither rewarding self-stimulation nor disruption of ongoing water drinking was produced. These results are congruent with evidence from lesion studies that the lateral septum normally acts to suppress reactivity and aggressiveness in the rat; they do not support previous suggestions that the medial septum is involved in the modulation of these behaviors.