DIFFERENT ROLES OF CATECHOLAMINERGIC AND SEROTONINERGIC NEURONS OF THE MEDIAL FOREBRAIN-BUNDLE ON MALE-RAT SEXUAL-BEHAVIOR

The medial forebrain bundle (MFB) plays an important role in the central elaboration of male sexual behavior in rats. The role of its ascending monoaminergic systems is not well understood. By selective lesions of catecholaminergic and serotoninergic axons of the MFB, produced with 6-OHDA and 5-7-DHT, resepctively, its possible involvement in male sexual behavior was studied. The evaluation of the behavioral patterns was studied by means of a microcomputer which also permitted the quanification of sequences in the sexual behavior patterns. Lesions with 5-7 DHT increased the intromission-ejaculation sequences and the percentage of ejaculatory males, without modifying other behavioral tests. Lesions with 6-OHDA diminished the number of active sexual patterns and motor activity. In order to check the specificity of the chemical lesions, the in vitro uptake of labeled norepinephrine and serotonin was measured. The 5-7 DHT lesioned rats showed a reduction in the uptake of 5-HT[serotonin]-14C in the MPOA [medial preoptic area]; the 6-OHDA group showed a reduction of NA[noradrenaline]-3H in the striatum.