Role of substance P in central control of ovulation in female rats.

OBJECTIVE To investigate the influence of substance P on gonadotropin release from the pituitary as evaluated according to the final effect, i.e. the ovulation. METHODS Stainless steel tube was implanted into the 3rd cerebral ventricle and substance P (SP), C-terminal hexapeptide of Substance P (SP6-11), Gn-RH and adrenaline were infused on the 3rd day of the cycle (proestrus). The oviducts were then isolated on the day of estrus and the ova were counted. RESULTS SP or SP6-11 inhibited the ovulation which was not prevented by intracerebroventricular (i.c.v.) capsaicin pretreatment. The i.c. v. administration of noradrenaline on the 7-8th day of pseudopregnancy induced the ovulation which was prevented by the injection of SP immediately before noradrenaline. CONCLUSIONS It is suggested that noradrenergic neuros which control the ovulation by influencing the release of Gn-RH into pituitary portal vessels are affected by SP-ergic neurons.