Effects of olfactory tubercle and corticomedial amygdaloid lesions upon sexual behavior of male rats paired with ovariectomized lures given estrogen or estrogen plus progesterone injections

Abstract

In male rats, removal of both main (MOB) and accessory (AOB) olfactory bulbs produces deficits in the initiation of sexual behavior as well as the ability to ejaculate. Lesions in the olfactory tubercle (OT) and corticomedial (CMA)-basomedial amygdala have produced deficits in the initiation of mating and the ejaculatory process, respectively. Anatomically, the AOB projects to the CMA while fibers from the MOB terminate in the OT. Therefore, sexual behavior initiation deficits following or lesions may be due to interruption of projections from the MOB while ejaculatory deficits following lesions including the CMA may result through destruction of AOB projections. The present experiment reassessed this possibility by performing lesions in areas of the OT and CMA receiving MOB and AOB projections, respectively. Lesions of the OT or CMA failed to produce the predicted effects when lures treated with estrogen plus progesterone were used. When lures treated with estrogen alone were used, or lesioned animals still failed to show an initiation deficit, However, CMA lesions produced ejaculatory deficits including lengthened ejaculatory latencies, increased mounts or intromissions per ejaculation, and lengthened interintromission intervals. Behavioral observations with the use of the two types of lures suggested that absence of soliciting behaviors in females given only estrogen may have accounted for CMA-lesion-produced deficits. Data from these experiments and other studies suggest that disruption of AOB projections to the amygdala was not the crucial factor in producing the ejaculatory deficits after lesions involving the CMA. It was suggested that the CMA may serve as a nodal point for integration of several sources of information related to the ejaculatory process.