For over two decades it has been hypothesized that supraspinal networks control sexual reflexes primarily by inhibitory mechanisms. While the majority of work has emphasized a role for the hypothalamus and midbrain in sexual behavior, little information is available concerning the medullary control of sexual reflexes in males. Recently, we have defined an area in the rostral region of the nucleus paragigantocellularis (nPGi) in the ventral medulla that controls the descending inhibition of spinal sexual reflexes in the male rat (Marson & McKenna 1990a). The immediate goal of these studies is to examine the role of the brainstem in the integration of autonomic and somatic systems involved in spinal sexual reflexes and to examine how brainstem pathways and mechanisms control the neural activity underlying sexual function. The long term goals of these studies are to understand CNS regulation of sexual function in response to environmental stimuli. The proposed studies will examine the hypothesis that the nPGi integrates autonomic and somatic activity subserving ongoing and reflex control of spinal sexual reflexes and will examine the putative neurotransmitters involved in the brainstem control of sexual reflexes. The proposed studies will consist of correlative neuroanatomical, neurophysiological and neuropharmacological experiments. The course and location of brainstem neurons projecting to the rostral nPGi, a region controlling the descending inhibition of spinal sexual reflexes will be mapped. Characterization of the neurotransmitter/s involved in the elaboration of spinal sexual reflexes will be identified using neuropharmacological and immunohistochemical techniques. The hypothesis that 5-hydroxytryptamine plays an inhibitory role in spinal sexual reflexes will be examined. Pathways from the medial preoptic area of the hypothalamus (MPOA) to the rostral nPGi will be mapped. These studies will provide an anatomical and functional link between the hypothalamus and the spinal cord in the control of sexual reflexes. The contribution of the medulla, MPOA and interconnecting sites, with respect pudendal, pelvic and hypogastric nerve activity, internal pudendal blood flow and activation of the 'coitus reflex' will be examined using chemical stimulation and lesions of anatomically identified brainstem neurons. Each study will advance the existing knowledge of the organization, integration and control of the brainstem mechanisms involved in male sexual reflexes. This proposal will examine how the medulla modulates spinal sexual reflexes which ultimately prepare the animal for the execution and completion of sexual function. New information concerning the anatomical, functional and chemical specificity/heterogeneity of pathways modulating sexual reflexes in the male will be gained. These studies have strong clinical implications providing treatment of sexual dysfunction, and for explaining the basis for relatively common dysfunction produced by therapeutic agents.
| Marson, L; List, M S; McKenna, K E (1992) Lesions of the nucleus paragigantocellularis alter ex copula penile reflexes. Brain Res 592:187-92 |
