Connections from the lateral septum modulating reactivity in the rat

Abstract

Rats made hyperreactive by lesions of the medial hypothalamus had an electrode implanted unilaterally into the region ventral to the anterior septum or into the lateral septum. Some of the animals with electrodes in the lateral septum then received a bilateral lesion ventral to the anterior septum while some of the animals with electrodes ventral to the anterior septum received a bilateral lesion in the lateral septum. Following recovery, each animal's level of reactivity was scored 5 min before, during, and 5 min following electrical stimulation at 20 μA (60 Hz). The suppression of reactivity by stimulation ventral to the anterior septum was not altered by a lesion of the medial and lateral septum. However, the suppression of reactivity by stimulation of the lateral septum was significantly attenuated by a lesion ventral to the anterior septum. The effectiveness of the lesion ventral to the anterior septum in attenuating the suppression of reactivity by lateral septal stimulation suggests that the neural pathway from the lateral septum which normally modulates reactivity courses anteriorly and ventrally from the septum.