Electrophysiological approach to the hypothalamic GnRH pulse generator

The hypothalamic GnRH pulse generator that regulates intermittent GnRH discharge into the pituitary portal circulation and thereby modulates pulsatile secretion of LH has been recognized as a key determinant of the reproductive function in mammals. Thus, various internal, as well as external, factors first modify the electrical activity of the GnRH pulse generator, which then alters the pulsatile pattern of gonadotrophin secretion and eventually influences reproductive function. Here, we describe a procedure that has permitted long-term recording of electrophysiological manifestation of the GnRH pulse generator activity and its application to our research which uses ovariectomized and cyclic female goats as experimental models. We have successfully recorded characteristic increases in neuronal activity associated with pulsatile LH secretion from conscious goats by means of a multiple unit activity (MUA) recording technique, which is an adaptation of that developed originally for use in rhesus monkeys. The unitary relationship between periodical increases in MUA (MUA volleys) and LH pulses is well maintained under a variety of experimental conditions, providing evidence that these MUA volleys are the consequence of GnRH pulse generator activity.