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Ejaculation is the final stage of coitus in the mammalian male and results in the expulsion of sperm out of the urethral meatus. Two successive phases, emission and expulsion, can be distinguished during ejaculatory response. Normal anterograde ejaculation requires close coordination of sympathetic, parasympathetic, and somatic components commanding the different peripheral anatomical structures (accessory sexual glands, ducti, and striated muscles) involved in ejaculation. The efferent pathways innervating these anatomical structures drive motor outputs originating from spinal thoracolumbar and lumbosacral nuclei. These spinal ejaculatory centers, the synchronized activation of which is likely carried out by a group of spinal cells, are under the control of both peripheral sensory afferents coming from genital areas and supraspinal information arising from specific brain regions.
Key Words: ejaculation, pharmacology, physiology, serotonin
Among the various physiological functions, those related to reproduction are probably uniquely essential for the survival of the species without being vital for the individual. Thus, from an evolutionary point of view, to experience orgasm concomitantly with ejaculation will best ensure perpetuation of the human race.
In recent years, male sexual dysfunctions have become an increasingly popular topic of interest in biological science. However, animal and clinical studies have focused on mechanisms and pathophysiology of penile erection and erectile dysfunction respectively, whereas the ejaculatory process and its dysfunctions have remained poorly investigated. The anatomical organization of the visceral organs involved in ejaculation shows a structure common in mammals, including humans. Therefore, the development of an experimental approach is useful for understanding the human physiology of ejaculation and may allow the discovery of potential pharmacological treatments applicable to human ejaculatory dysfunctions.
Ejaculation, commonly accompanied by orgasm, is the final stage of coitus in the mammalian male. Ejaculation is constituted by two successive phases, emission and expulsion, each of which involves different anatomical structures. A close coordination between sympathetic, parasympathetic, and somatic divisions of the nervous system is necessary for normal anterograde ejaculation to occur. The ejaculatory response involves sensory receptors and areas, afferent neural pathways, cerebral sensory and motor areas, spinal motor centers, and efferent pathways. The regulation of the ejaculatory reflex requires that neurochemically coordinated interrelationships take place at different levels of the neuraxis. Several neurotransmitter systems have been implicated in this process. The central serotonergic and dopaminergic...