Variations in the Release of LH in Response to Electrochemical Stimulation of Preoptic Area and of Medial Rasal Hypothalamus During the Estrous Cycle of the Rat1
- 1 September 1973
- journal article
- other
- Published by The Endocrine Society in Endocrinology
- Vol. 93 (3) , 665-669
- https://doi.org/10.1210/endo-93-3-665
Abstract
Electrochemical stimulation was performed at various stages of the estrous cycle and the release of LH estimated by the increase in plasma LH which occurred as a result of the stimulation. Plasma LH was determined by radioimmunoassay. Electrochemical stimulation of either the medial preoptic area (MPOA) or median eminence-arcuate region (ME-ARC) at 11 AM on proestrus produced dramatic elevations of plasma LH. On the other hand, similar stimulations carried out after the preovulatory surge of gonadotropins at 2300 hr were ineffective. If the preovulatory discharge of gonadotropins was blocked by treatment of the animals with Nembutal, the responsiveness to stimulation was partially restored. Stimulations of the MPOA or MEARC on diestrus day 1 produced only a slight elevation in plasma LH, whereas on diestrus day 2, there was a slightly greater response which was still much less than that obtained on the morning of proestrus. The cyclic variations in responsiveness to hypothalamic stimulation may reflect not only changes in pituitary sensitivity to the LH-releasing factor (LRF) released by the stimulation but also changes in the amounts of LRF released at various stages of the cycle. (Endocrinology93: 665, 1973)Keywords
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