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      Electrophysiological Characterization of GABA A Receptors in Anterior Pituitary Cells of Newborn Rats

      , ,

      Neuroendocrinology

      S. Karger AG

      Patch clamp, GABA, GABA receptors, Benzodiazepine

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          Abstract

          The γ-aminobutric acid (GABA)-ergic communication between the CNS and the anterior pituitary gland has been documented in numerous histochemical and biochemical studies but electrophysiological studies characterizing the GABA<sub>A</sub> receptor in the anterior pituitary are still lacking. In the present report we studied the GABA-induced current responses in cultured cells from the anterior pituitary gland of 6- to 10-day-old rats using the patch-clamp technique in the whole cell configuration. Fast application of GABA (100 µ M) induced membrane currents in 90% of cells in 2-day-old cultures. The EC<sub>50</sub> for GABA was 22.9 µ M and the Hill coefficient was 1.8. The responses to GABA (10 µ M) were inhibited by bicuculline (2 µ M) to 14%, by picrotoxin (5 µ M) to 21% and by zinc (10 µ M) to 33%. Inhibition to 56% was observed with 6 µ M strychnine. The GABA responses were sensitive to diazepam and pentobarbital. Half-maximal potentiation of responses to GABA (10 µ M) was found with 1.0 µ M diazepam and with 14.4 µ M pentobarbital. The maximal potentiation of GABA responses was 222% for diazepam and 195% for pentobarbital. Pentobarbital (100 µ M) did not induce any response in anterior pituitary cells in the absence of GABA. The application of GABA at concentrations 10 µ M or higher, induced membrane currents that desensitized. Desensitization proceeded as a biexponential process with estimated fast and slow time constants which decreased with concentration. The responses to GABA (300 µ M) desensitized to 93% with time constants of 1.4 and 5.3 s. Half-maximal desensitization was found with 13.4 µ M GABA. The recovery of GABA responses from desensitization proceeded as a single-exponential process. Responses induced by 300 µ M GABA, resensitized with a time constant of 20.8 s. We conclude that anterior pituitary cells possess GABA<sub>A</sub> receptors which exhibit the same pharmacological characteristics and desensitization kinetics but lower sensitivity to GABA as compared to those present in CNS neurones.

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          Author and article information

          Journal
          NEN
          Neuroendocrinology
          10.1159/issn.0028-3835
          Neuroendocrinology
          S. Karger AG
          0028-3835
          1423-0194
          1995
          1995
          09 April 2008
          : 62
          : 2
          : 123-129
          Affiliations
          Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
          Article
          126996 Neuroendocrinology 1995;62:123–129
          10.1159/000126996
          8584111
          © 1995 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
          Pages: 7
          Categories
          Cell Biology and Pharmacology of the Pituitary

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