Neuroendocrinology
Effects of Estrogen on Neuronal Excitability in the Hippocampal-Septal-Hypothalamic SystemKubo K. · Gorski R.A. · Kawakami M.2nd Department of Physiology, Yokohama City University School of Medicine, Yokohama
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Article / Publication Details
Received: December 13, 1974
Accepted: April 28, 1975
Published online: March 20, 2008
Issue release date: 1975
Number of Print Pages: 16
Number of Figures: 0
Number of Tables: 0
ISSN: 0028-3835 (Print)
eISSN: 1423-0194 (Online)
For additional information: https://www.karger.com/NEN
Abstract
The effects of electrical stimulation of the medial preoptic area (MPO) upon unit firing in the periventricular arcuate nucleus, and that of the dorsal hippocampus (DHPC) on medial septo-preoptic and arcuate (ARC) neurons, were investigated in Wistar and Sprague-Dawley female rats throughout the 4-day estrous cycle. Unit activity was recorded using stereotaxically-oriented tungsten microelectrodes under light urethane anesthesia. Repetitive stimulation of monophasic square waves varying only in current intensity was used. The following results were obtained: (a) An increase in activity of all ARC neurons recorded was induced by MPO stimulation on each day of the estrous cycle, (b) The minimum current (threshold) effective in increasing activity in the ARC neurons varied throughout the estrous cycle; the lowest threshold was observed in proestrus and the highest on the first day of diestrus. Also, the threshold current of MPO stimulation required to increase ARC activity was found to be elevated after ovariectomy and markedly reduced to the levels of the prcestrous animal by estrogen treatment, (c) Stimulation of the DHPC (field CA3) increased activity in the medial septum but decreased activity in the MPO. Two pools of neurons, one increased and one decreased by DHPC stimulation, were observed in the ARC. (d) Variation in the threshold hippocampal stimulation during the estrous cycle was observed in the response of MPO and ARC neurons (the stimulation was effective only in proestrus and estrus), but not in that of medial septal neurons, (e) In addition, the spontaneous activity of septal, MPO, and ARC neurons was increased at proestrus or after estrogen injection. The present results suggest that plasma levels of estrogen play an essential role in the cyclic process of the regulation of ovulation by way of the selective facilitation of neuronal excitability in specific functional neural pathways.
© 1975 S. Karger AG, Basel
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Article / Publication Details
Received: December 13, 1974
Accepted: April 28, 1975
Published online: March 20, 2008
Issue release date: 1975
Number of Print Pages: 16
Number of Figures: 0
Number of Tables: 0
ISSN: 0028-3835 (Print)
eISSN: 1423-0194 (Online)
For additional information: https://www.karger.com/NEN
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Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
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