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      Serotonin in Golden Hamster Testes: Testicular Levels, Immunolocalization and Role during Sexual Development and Photoperiodic Regression-Recrudescence Transition

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          Abstract

          Serotonin (5-HT) is found in the gonads and accessory reproductive organs of several species. The golden (Syrian) hamster is a seasonal breeder. Exposure of male adult hamsters to short days for 14 weeks results in a severe gonadal regression, while after a photoinhibition period of 22 weeks a spontaneous testicular recrudescence occurs. The aim of this study was to investigate the presence of 5-HT and its major metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the gonads of golden hamsters, its immunolocation and its physiological role in the testis. The influence of age and photoperiod was also analyzed. Hamsters of 23, 36, 46, 60 and 90 days of age were kept in long photoperiod (LP: 14:10 h light/dark), and adult animals were exposed either to LP or to short photoperiod (SP: 6:18 h light/dark) for 14 and 22 weeks. Testicular parenchyma and capsule levels of 5-HT and 5-HIAA increased significantly at ages of 36 and 60–90 days, but decreased markedly during the exposure of adult hamsters to SP for 14 and 22 weeks. Mast cells were found exclusively in the testicular capsule. The testicular number of mast cells increased concomitantly with age, but decreased in adult hamsters exposed to SP. Mast and Leydig cells presented 5-HT-positive immunoreactivity. During sexual maturation as well as during the transfer of adult hamsters from LP to SP, the 5-HIAA/5-HT ratio showed the highest values in active adult animals, indicating that the increase in testicular 5-HT levels in adulthood is accompanied by an augment in 5-HT turnover. In vitro basal and hCG-stimulated testosterone production was significantly inhibited in presence of physiological concentrations of 5-HT. In conclusion, the present studies demonstrate the existence of 5-HT in mast cells and Leydig cells of hamster testes, as well as describe an inhibitory action of this neurotransmitter on gonadal testosterone production. Furthermore, the age-dependent and photoperiodic-related changes detected in testicular 5-HT levels suggest that this neurotransmitter might act as an important local modulator of the action of gonadotropins on steroidogenesis during sexual development and during the photoperiodic regression-recrudescence transition in the golden hamster.

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          Most cited references 3

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          Effect of GABA and benzodiazepines on testicular androgen production.

          We have evaluated the effect of Ro5-4864, a selective probe to label peripheral type benzodiazepine receptor, on "in vitro" testicular androgen production. Decapsulated testes from adult rats showed a significant increase in the basal and hCG-stimulated testosterone secretion into the medium in response to 10(-5) M, 10(-6) M, and 10(-7) M Ro5-4864. In addition, we have studied the changes in testicular GABA content at three different ages and we found its highest concentration at 31 days of age. When we evaluated the effect of GABA on "in vitro" androgen production at different stages of gonadal maturation we observed that the highest concentration of GABA (10(-6) M) was able to modify the basal and hCG-stimulated androgen production from adult (60 days) and pubertal (45 days) testes. In addition, when prepubertal testes (31 days) were incubated under basal conditions, 10(-6) M GABA induced a significant increment of androstanediol production, while the stimulatory effect of hCG was reduced in the presence of the same GABA concentration. The present results suggest that GABA plays a physiological role in the regulation of rat testicular androgen production depending on the stage of sexual maturation.
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            Regulation of corticotropin-releasing factor secretion from Leydig cells by serotonin

             V. Tinajero (1992)
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              γ-aminobutyric acid in peripheral tissues

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                Author and article information

                Journal
                NEN
                Neuroendocrinology
                10.1159/issn.0028-3835
                Neuroendocrinology
                S. Karger AG
                0028-3835
                1423-0194
                1999
                April 1999
                21 April 1999
                : 69
                : 4
                : 299-308
                Affiliations
                aInstituto de Biología y Medicina Experimental, bFacultad de Medicina, UBA, cInstituto de Investigaciones Farmacológicas, CONICET and dCentro de Investigaciones en Reproducción, Facultad de Medicina, UBA, Buenos Aires, and eCátedra de Endocrinología, Facultad de Ciencias Exactas, UNLP, La Plata, Argentina
                Article
                54431 Neuroendocrinology 1999;69:299–308
                10.1159/000054431
                10207282
                © 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: 6, Tables: 1, References: 51, Pages: 10
                Categories
                Reproductive Neuroendocrinology

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