Suppression of VMH-lesion induced reactivity and aggressiveness by electrical stimulation ventral to the anterior septum in the rat

Animals made vicious with bilateral ventromedial hypothalamic lesions had bipolar electrodes implanted unilaterally ventral to the anterior septum just lateral to the diagonal band of Broca or in the lateral septum. Four days later, the animals' reactivity and aggressiveness was evaluated 5 min before, during, and 5 min following 30 sec of stimulation at 20 μA (60 Hz, sine wave). Stimulation of the region ventral to the septum or the lateral septum suppressed reactivity and aggressiveness by almost 70% compared to pre- and poststimulation levels. Stimulated control animals with electrodes in the accumbens nucleus, the diagonal band of Broca or adjacent to the medial septum did not behave differently than unstimulated control animals. Further tests with stimulation of the region ventral to the anterior septum at the 20 μA level showed that the stimulation did not produce either self-stimulation or disruption of ongoing eating. Recordings of electrical activity following the stimulation showed afterdischarge in only one animal. These results are congruent with evidence from lesion studies that the region ventral to the anterior septum as well as lateral septum normally acts to suppress reactivity and aggressiveness in the rat.