[Neurophysiological mechanisms of ejaculation].

The sexual behavior of the male can be described as a series of behavioral transitions eventually leading to ejaculation and sexual satisfaction. The ejaculation itself is extensively regulated by different ejaculation generators. The "spinal ejaculation generator" receives genito-sensory signals through afferent fibers and then informs the brainstem and forebrain via ascending fiber projections. Conversely, the supraspinal areas restrict ejaculations to the optimal moments and circumstances through descending afferent fibers. The messages ascending from the spinal cord reach the interconnected thalami, hypothalami, limbic system and cerebral cortex and are integrated with olfactory information. These brain areas are all related to ejaculation, but the exact facilitatory and inhibitory mechanisms involved have not yet been elucidated hitherto. Both the medial preoptic nucleus and brainstem areas play an important role in the "downward" mechanisms underlying the spinal "release" of an ejaculation. The medial preoptic nucleus is also precisely related to the "sexual rewarding" coming with an ejaculation. Meanwhile, the roles of several neurotransmitters are discussed considering their remarkable effects on ejaculation. This review focuses on the ejaculation-related circuits and neurotransmitters for the purpose of gaining a deeper insight into the mechanisms of ejaculation and providing some theoretical evidence for the study and treatment of ejaculation-related diseases.