0
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Evidence that Neuronal Nitric Oxide Synthase but Not Heme Oxygenase Increases in the Hypothalamus on Proestrus Afternoon

      Read this article at

      ScienceOpenPublisherPubMed
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Nitric oxide (NO) has been implicated in the control of the proestrus luteinizing hormone (LH) surge in the rat but to date no studies have attempted to measure neuronal nitric oxide synthase (nNOS) or NO production on proestrus in the hypothalamus in order to determine if endogenous NO is increased on proestrus afternoon to activate gonadotropin-releasing hormone (GnRH) neurons. To address this deficit in our knowledge, we measured nNOS mRNA and protein levels as well as NOS activity levels in rat preoptic area (POA) and medial basal hypothalamus (MBH) fragments at 12.00, 14.00, 16.00, and 18.00 h of proestrus. Serum LH levels were also assessed to determine whether NOS changes correlate to the LH surge. To determine the specificity of observed changes we also measured mRNA levels for the enzyme heme oxygenase-2, which is responsible for production of another putative gaseous transmitter, carbon monoxide. In all studies a metestrus 12.00 h control group was included since steroid and LH levels would be basal at this time as compared to proestrus. The results revealed that nNOS mRNA and protein levels, as well as NOS activity did not change significantly in the MBH on proestrus. In contrast, nNOS mRNA levels were significantly elevated in the POA at proestrus 12.00 and 14.00 h, as compared to metestrus 12.00 h. Likewise, at the protein and activity level, nNOS protein levels in the POA were significantly elevated on proestrus at 14.00 and 16.00 h, with NOS activity significantly increased at 16.00 h on proestrus. The elevation of nNOS protein and activity levels in the POA occurred at the time of initiation of the LH surge. The elevation of nNOS was specific as mRNA levels for the CO-synthetic enzyme heme oxygenase-2 did not change significantly on proestrus in the POA or MBH. As a whole, the current studies provide new evidence that nNOS is elevated in the POA on proestrus, and thus could play a role in the activation of GnRH neurons to produce the preovulatory LH surge.

          Related collections

          Most cited references 2

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

          Immunohistochemical mapping of nitric oxide synthase in the rat hypothalamus and colocalization with neuropeptides

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

            Nitric oxide mediates the stimulation of luteinizing-hormone releasing hormone release induced by glutamic acid in vitro

              Bookmark

              Author and article information

              Journal
              NEN
              Neuroendocrinology
              10.1159/issn.0028-3835
              Neuroendocrinology
              S. Karger AG
              0028-3835
              1423-0194
              1999
              November 1999
              17 November 1999
              : 70
              : 5
              : 360-367
              Affiliations
              Department of Physiology and Endocrinology, School of Medicine, Medical College of Georgia, Augusta, Ga., USA
              Article
              54497 Neuroendocrinology 1999;70:360–367
              10.1159/000054497
              10567862
              © 1999 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, References: 32, Pages: 8
              Categories
              Regulation of Gonadotropins

              Comments

              Comment on this article