Comparative study of the pelvic ganglion in adult and in developing, male and female rats

The development and comparison of structural features of the pelvic ganglion in male and female rats was investigated with morphometric and histochemical techniques in light and electron microscopes. Pelvic ganglia from adult rats were sexually dimorphic in volume (approximately 0.3mm³ in the male and 0.18mm³ in the female), neuron number (12,506 ± 668 neurons in the male and 6,845 ± 717 in the female) and average neuron size. At three weeks of age ganglion volume and neuron number were similar to the adult and were, therefore, already distinctly sexually dimorphic, although the smaller average neuron size showed no gender difference. In contrast, at birth pelvic ganglia revealed no gender-related differences in either volume, neuron number or size. Whereas ganglion volume and neuronal size were less than in the older animal groups, neuron numbers in newborn ganglia from both sexes were similar to those in adult male rats. Ganglia from adult males that had been castrated before puberty, were similar in volume and neuron number to unoperated animals, although neuronal size was significantly reduced. Neuronal death was observed in ganglia from newborn rats at similar extents in both sexes. Apoptotic neurons were also present in ganglia from 7-day old rats, when the extent of cell loss appeared greater in the female than in the male. It is concluded that the main features of the sexual dimorphism in the pelvic ganglion become established after birth and before puberty. Increasing testosterone levels in the early post-natal period probably influence the ontogeny of the pelvic ganglion, acting either directly on the neurons, or indirectly via trophic factors released from developing pelvic organs. Evidence suggests that target-derived factors, effected by hormone or not, play a role in neuronal survival and neuronal growth in the pelvic ganglion