Peripheral autonomic regulation of gonadotropin secretion in pubertal rats. Inhibition of post-castration rise of gonadotropins during wallerian degeneration after sympathetic superior cervical ganglionectomy

Abstract

Shortly after superior cervical ganglionectomy (SCGx) peripheral sympathetic nerve terminals in the median eminence degenerate, the neurotransmitter is released, and a transient period of increased postsynaptic ensues. The present experiments were undertaken to examine, in the anterograde degeneration paradigm after SCGx, the participation of peripheral sympathetic nerves in feedback regulation of gonadotropin release in pubertal rats. Groups of 18 days old or 26 days old rats of both sexes were subjected to castration or its sham-operation, and 4 h later to SCGx or sham-SCGx. Twenty-four h later, the rats were decapitated and serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were measured by RIA. In 19 days old male rats, the post-castration increase of circulating LH, but not of FSH, was prevented by the wallerian degeneration of sympathetic nerves after acute SCGx. At the 27th day of life, acute SCGx prevented FSH, but not LH, post-orchidectomy rise. In female rats, SCGx blunted the oophorectomy-induced increase of gonadotropin levels at both examined ages. SCGx brought about a significant decrease of serum LH levels in 19 days old, sham-castrated female rats. At the 19th day of life, acute SCGx decreased serum LH and FSH in neonatally orchidectomized rats, but not in neonatally androgenized female rats. The data are in favor of a negative influence of peripheral sympathetic neurons on gonadotropin release in prepubertal rats, predominantly in female rats.