Pulsatile luteinizing hormone (LH) secretion is impaired after posterior anterior-hypothalamic deafferentation (PAD), which separates the anterior part of the arcuate nucleus from the mediobasal hypothalamus (MBH). In the present study, we examined whether transplants of fetal brain tissue could prevent the effects of PAD. The brain tissue containing the MBH or the cerebral cortex taken from the fetal brain was transplanted into the third ventricle of ovariectomized rats. Four weeks after the brain transplantation, animals with or without the brain transplantation were subjected to PAD. One week after PAD, blood samples were collected every 6 min for 3 h through an indwelling atrial cannula. Rats bearing PAD without transplantation showed irregular pulsatile fluctuation of plasma LH, whereas LH pulses were maintained in rats bearing transplantation of the fetal MBH tissue. In rats which had been transplanted with the cerebral cortex, LH pulses were less apparent after PAD than in the MBH-transplanted or sham-deafferentated animals. No cell bodies of LH-releasing hormone (LHRH) neurons were found immunohistochemically 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.