Influence of the paraventricular nucleus and oxytocin on the retrograde stain of pubococcygeus muscle motoneurons in male rats.
Lumbosacral cord motoneurons innervating the pubococcygeus muscle (Pcm) at the pelvic floor of male rats were analyzed. We showed previously that these motoneurons participate in sexual functions and are sensitive to fluctuations of systemic androgen and estrogen. Though estrogen receptors have not been identified in Lamina IX at these spinal areas, the release of oxytocin from the paraventricular nucleus of the hypothalamus (PvN) has been found to control pelvic sexual physiology. We therefore worked on the hypothesis that steroid hormones in the PvN induce the release of oxytocin at the lumbosacral level to modulate the function of Pcm motoneurons. Four experiments were developed, and results were observed with the retrograde staining of motoneurons with horseradish peroxidase. Data indicated that morphometric parameters of Pcm motoneurons were significantly reduced after castration or blocking of the steroids at the PvN site, or following complete transection of the spinal cord at the T8 level. In each case, the reduction of the stain was recovered after intrathecal treatment with oxytocin. Thus, present results show that Pcm motoneurons respond to spinal oxytocin. The conclusive model that we propose is that steroids stimulate the PvN, causing the nucleus to release oxytocin at the level of the lumbosacral spinal cord, and the release of the peptide regulates the spread of the stain of Pcm motoneurons. This work also shows that motoneurons distal to a transected area in the spinal cord could respond to exogenous oxytocin, an important finding for the research of spinal cord lesioned subjects.
Pérez
César Antonio
CA
Instituto de Neuroetologia, Universidad Veracruzana, A.P. 566, Xalapa, Ver. 91000, Mexico.
Concha
Adriana
A
Hernández
María Elena
ME
Manzo
Jorge
J
D000818:Animals; D001141:Aromatase / Q000502:physiology; D002369:Castration; D012739:Gonadal Steroid Hormones / Q000502:physiology; D008161:Lumbosacral Region / Q000033:anatomy & histology; D008297:Male; D009046:Motor Neurons / Q000166:cytology* / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D010121:Oxytocin / Q000378:metabolism* / Q000502:physiology; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D017773:Pelvic Floor / Q000294:innervation* / Q000502:physiology; D051381:Rats; D012183:Retrograde Degeneration / Q000473:pathology; D012726:Sexual Behavior, Animal / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology; D013194:Staining and Labeling
D012739:Gonadal Steroid Hormones; D010121:Oxytocin; D001141:Aromatase