To examine the effects of bilateral cervical sympathectomy on the secretion of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) and testosterone (TS), 24 male rats were divided into four groups: control (C), light (L), sympathectomy (S), and light-sympathectomy (LS) groups. The C and S groups were kept under a 12-h light-dark cycle and the L and LS groups were kept under continuous light for 2 weeks. After 2 weeks, blood was collected and the rats were perfused with a fixative. GnRH neurons in the hypothalamus were stained immunohistochemically, and serum LH and TS levels were measured by radioimmunoassay. Although the difference in the number of GnRH neurons between the C and S groups was not significant, the L group was significantly lower than the C or LS groups. The serum LH and TS levels in the L group were higher than in the other groups. The present results suggest that continuous light increases GnRH secretion in the hypothalamus, followed by increased secretions of LH in the pituitary and TS in the testes, and bilateral cervical sympathectomy under continuous light inhibits these hormonal changes. However, a normal circadian rhythm does not affect gonadotropin secretion. Therefore, long-term and repeated stellate ganglion block may inhibit the increases of GnRH, LH, and TS secretions induced by continuous light.
Keywords: Cervical sympathectomy; Gonadotropin; Rat; Stellate ganglion block; Testosterone.