REGULATION OF GONADAL-STEROID RHYTHMS IN RATS

This review clearly demonstrates the coupling of the adrenal and gonadal hormone rhythmicities. The physiological significance of this coupling is subject to considerable speculation. It is possible that adrenal secretions provide a transient period of quiescence or heightened gonadal secretion which may be important in reproductive performance and synchronization with other biological clocks. A breakdown in this interrelationship between the endocrine glands due to factors such as environment, stress (internal or external) or others may herald reproductive senescence. These studies also firmly establish the concept that gonadal steroids are able to modify hypothalamic LHRH activity. In this respect, while androgens and oestrogens were equipotent there was an indication that the central field of androgen action as compared to that of oestrogen may be restricted to the basal hypothalamus. The preoptic area (POA) LHRH neurons and their innervation to the organum vasculosum of lamina terminalis (OVLT) were resistant to steroid action. This raised the possibility of the existence of more than one population of LHRH neurons. Our studies suggest that only those LHRH neurons which project into the median eminence possess the ability to respond to changes in steroid titre. © 1979.