5-hydroxytryptamine(2C) receptors on spinal neurons controlling penile erection in the rat

The localization of 5-hydroxytryptamine(2C) receptors in the lumbosacral sp inal cord of the rat was investigated using selective antibodies raised aga inst the carboxyl-terminal part of the rat receptor. The distribution of im munoperoxidase labelling at the light microscope level revealed numerous la belled neurons in the gray matter, with a higher intensity in the sacral pa rasympathetic nucleus, the dorsal gray commissure and particularly the moto neurons of the ventral horn. Confocal microscope analysis showed that immun ostaining was mainly intracellular (motoneurons), but could also be associa ted with the membrane of cell bodies and dendrites. Actually, electron micr oscope immunogold experiments demonstrated an exclusive staining of the cis -Golgi apparatus. Following pseudo-rabies virus transsynaptic retrograde la belling from the corpus cavernosum, labelled neurons were found in the sacr al parasympathetic nucleus and the dorsal gray commissure of the L6-S1 segm ents, All virus-labelled neurons exhibited 5-hydroxytryptamine(2C) receptor immunoreactivity. These results indicate that all parasympathetic pregangl ionic neurons and their related interneurons which contribute to the innerv ation of cavernosal tissue bear 5-hydroxytryptamine(2C) receptors. In the s acral parasympathetic nucleus, most neurons which were retrogradely-labelle d from the pelvic ganglion with Fast Blue also showed 5-hydroxytrypramine(2 c) receptor immunoreactivity. In the ventral horn, motoneurons retrogradely labelled from the ischiocavernosus muscle and the bulbospongiosus muscle, both of which are involved in erection and ejaculation, were also 5-hydroxy tryptamine(2C) receptor-immunopositive. The supraspinal serotoninergic control of erection at the lumbosacral level therefore appears to be strongly associated with the activation of 5-hydro xytryptamine(2C) receptors, consistent with the proerectile properties of 5 -hydroxytryptamine(2C) agonists. (C) 1999 IBRO. Published by Elsevier Scien ce Ltd.