title: Neural mechanisms of sexual behavior in the male rat: emphasis on ejaculation-related circuits.
abstract: Sexual behavior of the male rat can be described as a 'sequence': a series of behavioral transitions eventually leading to a consummatory act: ejaculation. A 'funnel-model' is presented to describe the behavioral progression during the sexual sequence. The ejaculation itself is extensively controlled by the 'spinal ejaculation generator', consisting of several elements with afferent sources of genitosensory information, with ascending projection fibers to inform the brainstem and forebrain as well as with descending afferent fibers providing the supraspinal control mechanisms with the opportunity to restrict ejaculations to the optimal moments and circumstances. The messages ascending from the spinal cord reach several interconnected thalamic, hypothalamic and limbic brain areas and are integrated with olfactory information. These brain areas play a role in mechanisms like 'sexual satiety' or a temporary interruption of sexual activities (post-ejaculatory interval), but the exact facilitatory and inhibitory mechanisms involved have not been elucidated yet. In the 'downward' mechanisms controlling the spinal 'release' of an ejaculation, the medial preoptic nucleus plays an important role in cooperation with a number of brainstem areas. This nucleus is also explicitly involved in the rewarding experiences coming with an ejaculation. Finally, the role of several neurotransmitters and-peptides on male sexual behavior are discussed shortly, because sometimes they show remarkable effects on specific aspects of the behavioral sequence. We conclude that, despite our increased knowledge about the brain mechanisms involved in the control of ejaculation, we are still far away from a complete understanding and quite a few questions remain to be resolved.
authors.affiliation: Dept. of Anatomy, Radboud University Medical Center, Nijmegen, The Netherlands; Dept. of Psychopharmacology, UIPS, University of Utrecht, The Netherlands.
authors.forename: J G
authors.initials: JG
authors.lastname: Veening
authors.affiliation: Dept. of Physiology & Biophysics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA; Dept. of Neurobiology & Anatomical Sciences, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Coolen
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology; D004298:Dopamine / Q000502:physiology; D004542:Ejaculation / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D010121:Oxytocin / Q000502:physiology; D051381:Rats; D012701:Serotonin / Q000502:physiology; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology; D001615:beta-Endorphin / Q000502:physiology
chemical_list: D012701:Serotonin; D010121:Oxytocin; D001615:beta-Endorphin; D004298:Dopamine; D009638:Norepinephrine
keywords: Amygdala; Bed nucleus stria terminalis; Male sexual behavior; Medial preoptic area; Reward; Spinal reflex generator