EFFECTS OF TRANSPLANTS OF FETAL MEDIOBASAL HYPOTHALAMUS ON LUTEINIZING-HORMONE PULSES IMPAIRED BY HYPOTHALAMIC DEAFFERENTATION IN ADULT OVARIECTOMIZED RATS

Pulsatile luteinizing hormone (LH) secretion is impaired after posteri or anterior-hypothalamic deafferentation (PAD), which separates the an terior part of the arcuate nucleus from the mediobasal hypothalamus (M BH). In the present study, we examined whether transplants of fetal br ain tissue could prevent the effects of PAD. The brain tissue containi ng the MBH or the cerebral cortex taken from the fetal brain was trans planted into the third ventricle of ovariectomized rats. Four weeks af ter the brain transplantation, animals with or without the brain trans plantation were subjected to PAD. One week after PAD, blood samples we re collected every 6 min for 3 h through an indwelling atrial cannula. Rats bearing PAD without transplantation showed irregular pulsatile f luctuation of plasma LH, whereas LH pulses were maintained in rats bea ring transplantation of the fetal MBH tissue. In rats which had been t ransplanted with the cerebral cortex, LH pulses were less apparent aft er PAD than in the MBH-transplanted or sham-deafferentated animals. No cell bodies of LH-releasing hormone (LHRH) neurons were found immunoh istochemically in the MBH grafts. These results suggest that the graft containing the fetal MBH tissue maintains regular LH pulses after PAD and that the LHRH pulse generator may consist, at least in part, of a group of neurons in the MBH other than LHRH-producing neurons.