| Co-Investigator(Kenkyū-buntansha) |
FUNABASHI Toshiya Yokohama City University, School of Medicine, Instructor, 医学部, 助手 (70229102)
HIRUMA Hiromi Yokohama City University, School of Medicine, Instructor, 医学部, 助手 (10238397)
ENDO Yutaka Yokohama City University, School of Medicine, Instructor, 医学部, 講師 (90194050)
ARITA Jun Yokohama City University, School of Medicine, Associate Professor, 医学部, 教授 (80128587)
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| Research Abstract |
A series of electrophysiological experiments was performed in female rats to examine the possibility that the LHRH neuron involved in the tonic secretion of LH is distinct from that involved in the phasic secretion and the following results were obtained.
1. The LHRH pulse generator whose electrical activity is recorded in the median eminence of the ovariectomized rat seems to be able to work autonomously, but receives neuromodulations of (1) noradrenaline (NA) that causes a facilitatory regulation, (2) opioid that probably causes a direct inhibition on LHRH neurons in addition to the presynaptic inhibition on NA neurons, the latter mediating the negative feedback action of estrogen and environmental stimuli, and (3) GABA that has probably a small, minor role in the fine tuning of the generator.
2. The tonic secretion of LH is probably regulated by the same LHRH pulse generator as found electrophysiologically in the ovariectomized condition, and then the autonomy is strong, not affected by changes in NA.
3. The phasic secretion of LH is probably controlled by an LHRH surge generator whose LHRH neurons and neuromodulations are distinct from those in the pulse generator. Probably, there are LHRH neurons, other than those involved in tonic LH secretion, on which inhibitory modulations of GABA will progressively increase with the increase of estrogen in blood, since bicuculline infusion in the morning of proestrus induces an acute increase in LH secretion. However, even at this stage, the LHRH pulse generator involved in tonic secretion is considered to be working steadily.
Taking together, it is strongly suggested that the tonic and phasic secretion of LH are controlled by different subtype LHRH neurons and networks, respectively.
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