Gender and gonadectomy influence on neurons in superior cervical ganglia of sexually mature rats.

Gonadal hormones have a significant influence on both the number of neurons and the density of synapses in the superior cervical ganglion (SCG) during the early postnatal period. There are no studies reporting influence of the absence of these factors in sexually mature animals, although changes in SCG-neurons of the rat were observed up to 6 months of age. Hence, we investigated whether gonadectomy of sexually mature rats influences morphological properties of neurons in the SCG of the rat and if so, would it have a specific effect on neurochemically distinct subpopulations. Male and female Sprague-Dawley rats were gonadectomized at the age of two months. After 30 days, they were sacrificed and SCGs were harvested and processed immunohistochemically. The mean diameter of NPY- neurons was greater in male rats, in comparison to all other groups (p<0.05). The number of NPY+, NPY- and total neurons per section area was significantly higher in female than in male, orchidectomized or the ovariectomized animals (p<0.05). The share of the different neuronal populations in the SCG that were encircled with calretinin-positive baskets (c.b+) or c.b.- (NPY+ or NPY-) was significantly influenced by the gender of the animals and gonadectomy, with significantly more c.b.+ in male animals (p<0.05). Results of the present study indicate that substantial changes in the SCG neurons of the rat occur after reaching sexual maturity, and are influenced by the gonadectomy.