HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal My Folders Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Goodman, R. L. Articles by Malpaux, B. Search for Related Content PubMed PubMed Citation Articles by Goodman, R. L. Articles by Malpaux, B. Agricola Articles by Goodman, R. L. Articles by Malpaux, B.

Estradiol Increases Multiunit Electrical Activity in the A15 Area of Ewes Exposed to Inhibitory Photoperiods¹

^a INRA, Physiologie de la Reproduction et des Comportements, 37380, Nouzilly, France ^b Department of Physiology, West Virginia University, Morgantown, West Virginia 26506

ABSTRACT

Seasonal anestrus in ewes results from an increase in response to the negative feedback action of estradiol (E₂). This increase in the inhibitory effects of E₂ is controlled by photoperiod and appears to be mediated, in part, by dopaminergic neurons in the retrochiasmatic area of the hypothalamus (A15 group). This study was designed to test the hypothesis that E₂ increases multiunit electrical activity (MUA) in the A15 during inhibitory long days. MUA was monitored in the retrochiasmatic area of 14 ovariectomized ewes from 4 h before to 24 h after insertion of an E₂-containing implant subcutaneously. In six of these ewes, MUA activity was also monitored before and after insertion of blank implants. Three of the 14 ewes were excluded from analysis because E₂ failed to inhibit LH. When MUA was recorded within the A15, E₂ produced a gradual increase in MUA that was sustained for 24 h. Blank implants failed to increase MUA in the A15 area, and E₂ did not alter MUA if recording electrodes were outside the A15. These data demonstrate that E₂ increases MUA in the A15 region of ewes and are consistent with the hypothesis that these neurons mediate E₂ negative feedback during long photoperiods.

FOOTNOTES

First decision: 26 April 2000.

¹ R.L.G. supported by NIH-HD17864 and NIH-FO6-TWO2219.

² Correspondence: Robert L. Goodman, Department of Physiology, West Virginia University Health Sciences Center, Morgantown, WV 26506-9229. FAX: 304 293 3850; bgoodman{at}hsc.wvu.edu

This article has been cited by other articles:

				A. L. Bogusz, S. L. Hardy, M. N. Lehman, J. M. Connors, S. M. Hileman, J. H. Sliwowska, H. J. Billings, C. J. McManus, M. Valent, S. R. Singh, et al. Evidence that {gamma}-Aminobutyric Acid Is Part of the Neural Circuit Mediating Estradiol Negative Feedback in Anestrous Ewes Endocrinology, June 1, 2008; 149(6): 2762 - 2772. [Abstract] [Full Text] [PDF]

				C. J McManus, M. Valent, S. L Hardy, and R. L Goodman Does nitric oxide act in the ventromedial preoptic area to mediate oestrogen negative feedback in the seasonally anoestrous ewe? Reproduction, July 1, 2007; 134(1): 137 - 145. [Abstract] [Full Text] [PDF]

				V. L. Adams, R. L. Goodman, A. K. Salm, L. M. Coolen, F. J. Karsch, and M. N. Lehman Morphological Plasticity in the Neural Circuitry Responsible for Seasonal Breeding in the Ewe Endocrinology, October 1, 2006; 147(10): 4843 - 4851. [Abstract] [Full Text] [PDF]

				G. M. Anderson, S. L. Hardy, M. Valent, H. J. Billings, J. M. Connors, and R. L. Goodman Evidence that Thyroid Hormones Act in the Ventromedial Preoptic Area and the Premammillary Region of the Brain to Allow the Termination of the Breeding Season in the Ewe Endocrinology, July 1, 2003; 144(7): 2892 - 2901. [Abstract] [Full Text] [PDF]