Effects of Serotonin on Spontaneous Ovulation in Rats

Abstract

THE hypothalamus is particularly rich in biogenic amines—serotonin, dopamine and norepinephrine—but their role in the reproductive processes is not well understood¹. Most of these amines are located in the nerve terminals many of which end in the region of the median eminence¹. In recent experiments infusion of dopamine into the third ventricle stimulated the release of luteinizing hormone (LH) whereas a similar infusion of serotonin decreased it². This has given rise to the speculation that dopamine may function as a transmitter for the release of luteinizing hormone releasing factor (LH–RF) while inhibitory influences may be mediated through serotonin. The latter possibility is supported by the fact that serotonin has inhibitory effects on ovulation induced by gonadotrophins in immature mice³ and rats⁴. We have now examined the effects of this amine on spontaneous ovulation in adult rats with a 4 day oestrous cycle.