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      • Record: found
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      Electrical Activity of the Pulse Generator of Gonadotropin-Releasing Hormone in 26-Month-Old Female Rats

      ,

      Neuroendocrinology

      S. Karger AG

      Gonadotropin-releasing hormone, Aging, Electrophysiology, Pulsatile release, Gonadotropins, Rhythms

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          Abstract

          To know whether age-related changes occur in the activity of the pulse generator of gonadotropin-releasing hormone (GnRH), old (26 months) and young (3 months) female rats were examined by recording multiunit activity (MUA) in the median eminence region of the hypothalamus, concurrently with blood samplings through an intra-atrial cannula at 6-min intervals to determine serum luteinizing hormone (LH) concentrations. We have regarded the MUA showing intermittent increases (volleys) at 20–30 min intervals, followed by LH pulses, as the electrical activity of the GnRH pulse generator. We were successful in recording MUA in 18 (26%) of 69 old ovariectomized rats and in 8 (32%) of 25 young ovariectomized rats. The overall mean (±SE) of the interval between MUA volleys in old ovariectomized rats was 35.1 ± 2.0 min (n = 18), which was significantly longer than that of 22.5 ± 1.5 min (n = 8) in young ovariectomized rats. The mean interval between LH pulses in old ovariectomized rats was 32.2 ± 3.6 (n = 10), also being significantly longer than that of 23.3 ± 1.0 (n = 8) in young ovariectomized rats. Further, the LH pulse amplitude in old rats (0.95 ± 0.07 ng/ml) was significantly smaller than in young rats (3.40 ± 0.36 ng/ml). The present study also confirmed that the increase in serum LH after intravenous injection of 50 ng GnRH was much smaller in old ovariectomized rats. These results show that the electrical activity of the GnRH pulse generator is certainly reduced with age. Taken together with findings suggesting an age-dependent decrease in stimulated transmitter release, attenuation in both frequency and amplitude of GnRH pulses as well as in pituitary responsiveness to GnRH pulses may account for the decreased pulsatile LH secretion observed in aging rats.

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          Most cited references 7

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          • Abstract: found
          • Article: found

          Pulsatile Gonadotropin-Releasing Hormone (GnRH) Secretion Is an Inherent Function of GnRH Neurons, as Revealed by the Culture of Medial Olfactory Placode Obtained from Embryonic Rats

          To determine whether gonadotropin-releasing hormone (GnRH) neurons in culture without the hypothalamus secrete GnRH in a pulsatile fashion, the nasal placode (NAP) was obtained at day 13.5 of gestation and cultured by a roller tube method. If the GnRH release occurs in a pulsatile fashion, it can be said that the pulse generator of GnRH exists inherently in each cell or community of cells in the culture. The concentration of GnRH in the NAP culture medium collected at 8-min intervals for 160 min after 2- to 4-week cultures showed that GnRH release occurred in a pulsatile fashion with a mean interpulse interval of 29.8 ± 2.3 min (n = 9). When the NAP was cultured with tissues of the forebrain vesicle (n = 3) or the hypothalamus (n = 4), GnRH was also released in a pulsatile fashion with similar intervals (27.3 ± 1.0 min for the NAP+forebrain vesicle culture and 36.0 ± 6.3 min for the NAP+hypothalamus culture) as those in cultures without brain tissues. It is concluded that pulsatile GnRH release is an inherent function of GnRH neurons.
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            • Abstract: not found
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            LHRH neurons in the female C57BL/6J mouse brain during reproductive aging: No loss up to middle age

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              • Record: found
              • Abstract: not found
              • Article: not found

              Changes in neurotransmitter actions in the aged rat hippocampus

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                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                2000
                October 2000
                27 October 2000
                : 72
                : 4
                : 199-207
                Affiliations
                Department of Physiology, Yokohama City University School of Medicine, Yokohama, Japan
                Article
                54588 Neuroendocrinology 2000;72:199–207
                10.1159/000054588
                11070423
                © 2000 S. Karger AG, Basel

                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. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 5, Tables: 3, References: 42, Pages: 9
                Categories
                Hypothalamic Neurons: Regulation and Gene Expression

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