Effects of Active Immunization against Gonadotrophin-Releasing Hormone on the Concentrations of Noradrenaline, Dopamine, 5-Hydroxytryptamine and Some of Their Metabolites in the Brain and Sexual Organs of Male Rats

Abstract

This is an investigation of the effects of active immunization against gonadotrophin-releasing hormone (GnRH) conjugated to keyhole limpet hemocyanin on brain and male sexual organ concentration of catecholamines and 5-hydroxytryptamine. The treatment induces antibodies against GnRH with consequent interference with reproductive function as indicated by the attendant decrease in serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone. Rat striatal and mesolimbic dopamine levels were moderately increased by this treatment but no changes were observed in the hypothalamus. GnRH immunization also increased brain 5-hydroxytryptamine concentrations as observed in the hypothalamus, olfactory tubercles and striatum. In the male accessory sexual organs, immunity against GnRH alters the density of noradrenergic concentration. The changes occurred in opposite directions in the different regions investigated; increases in noradrenaline were observed in the prostate, with a reduction being detected in the epididymus and no changes were observed in the vas deferens or the seminal vesicles. 5-Hydroxytryptamine levels increased in the vas deferens but no effects were observed in the epididymus, prostate or seminal vesicle. It is concluded that GnRH immunization with the consequent reductions in circulating FSH, LH and testosterone are associated with changes in neurotransmitter concentration both in the brain and in some of the accessory sexual organs in the male rat.