Male sexual behavior is a complex behavior consisting of several different components. The mechanisms underlying erectile and ejaculatory function has been subject of investigation in many species, including man. However, the central control of ejaculation remains poorly understood. It is well established that ejaculation is a reflex and the central components necessary to complete this reflex are located in the lumbosacral spinal cord. This spinal ejaculatory neural system is under descending influence from supraspinal centers. However, ejaculatory reflexes remain intact when supraspinal inputs are interrupted, suggesting the existence of a spinal ejaculation generator. Until recently, the precise anatomical location and neurochemical identity of neurons that comprise the ejaculation generator has been unknown. Recently, we provided evidence that a population of lumbar spinothalamic (LSt) neurons plays a pivotal role in generation of ejaculatory behavior, suggesting that these cells form a critical component of the ejaculation generator. Moreover, preliminary data indicates that LSt cells have additional characteristics consistent with their role as a component of an ejaculation generator. In particular, these cells receive sensory inputs related to the onset of ejaculation and in turn project to preganglionic sympathetic and parasympathetic neurons in the lumbosacral spinal cord that mediate components of ejaculation. Thus, LSt cells appear to be in the position to integrate and coordinate inputs during sexual activity and outputs needed to trigger ejaculation. These discoveries provide, for the first time, a rich target for investigating the neural organization of ejaculation. In the current proposal we propose multidisciplinary studies utilizing neuroanatomical, physiological, pharmacological, and behavioral techniques, to further investigate the mating related inputs to LSt cells (Specific Aim 1), the efferent outputs of LSt cells (Specific Aim 2), and the sources of supraspinal influence on LSt neurons (Specific Aim 3). These studies will provide further insight into the spinal mechanisms involved in control of the ejaculatory reflex. Detailed understanding of a spinal ejaculation generator will significantly benefit treatment of sexual dysfunction, in particular related to ejaculation. Moreover, these studies will provide novel insights into the mechanisms regulating coordination of sensory, autonomic, and motor systems in the spinal cord.
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