A self-priming effect of luteinizing hormone releasing hormone on follicle-stimulating hormone secretion in the adult male rat.

In order to determine whether male rats show a self-priming effect of LHRH on FSH secretion, young adult male rats were anesthetized with ketamine HCl and injected intravenously with 50 ng LHRH/100 g body weight at 30- or 60-min intervals. Blood samples were collected by heart puncture and analyzed for FSH by radioimmunoassay. Animals injected at 30-min intervals released more FSH in response to the third and fourth injection than in response to the first. Castration 4 days prior to testing eliminated this response. Treatment of castrated male rats with a testosterone-filled Silastic capsule large enough to maintain secondary sexual organ weights and serum FSH concentrations at levels similar to those found in intact animals maintained the response. A smaller testosterone capsule did not. These data indicate that a self-priming effect of LHRH on FSH secretion exists in the adult male rat. This response requires something from the testes, probably testosterone, for its maintenance.