Immunoreactivity of Androgen Receptor Protein in Sexually Dimorphic Spinal Motonucleus in Neonatal Male Rats

Han, Sang Won; Choi, Seung Kang; Lee, Won Taik; Ma, Sang Yul; Cboi, Hyung Ki

Abstract

The spinal motonucleus of genitofemoral nerve regulating scrotal temperature also can be related to prenatal and neonatal testicular descent by gubernacular change in rats, and sexually dimorphic like bulbocavernosus/dorsolateral motonucleus. There is a hypothesis that neonatal androgen affects these motonuclei, and induce development of sexual organ through neural stimulation. Until now, the accumulation of isotope labeled androgen and immunoreactivity of androgen receptor protein in each sexually dimorphic spinal motonucleus have been revealed in adult rats but not been established in rats of neonatal periods. To investigate the presence of the androgen receptor in spinal sexually dimorphic motonuclei in neonatal period, we evaluated the androgen receptor immunoreactivity of these motonuclei. In Sprague-Dawley male rats, the lumbar spinal cords were resected according to cord level by laminectomy under dissecting microscope after perform aldehyde perfusion fixation at postnatal day3 (n=6), 10 (n=7) and 30 (n =6). The resected spinal cords were serially sectioned 50 um thick by vibratome, and stained immunohistochemically using polyclonal antibody of androgen receptor protein. The immunoreactivity of androgen receptor protein was observed in the cells of genitofemoral motonucleus from the thirteenth thoracic to the second lumbar spinal cord and bulbocavernosus/ dorsolateral motonucleus was observed from the 4th to 5th lumbar spinal cord at all age groups. The proportional areas of both motonuclei of day 3 and 10 on cross section were larger than that of day 30. The motonuclei of day 3 and 10 were more laterally located, compared to that of day 30. The immunostaining densities were similar in all age groups. With the above results, the presence of androgen receptor protein was confirmed in the genitofemoral and bulbocavernosus/ dorsolateral motonucleus from neonate to day 30. The larger proportional area of these motonuclei in neonates may indicate active role of these motonuclei during neonatal period. Although the immunoreactivity does not directly imply the presence of functional receptor, neonatal androgen could be responsible for the development of sexual organ through the spinal motonucleus.