+1 Recommend
1 collections
      • Record: found
      • Abstract: found
      • Article: found

      Biochemical Indices of Tuberoinfundibular Dopaminergic Neuronal Activity during Lactation:A Lack of Response to Prolactin

      Read this article at

          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.


          Serum concentrations of prolactin and biochemical estimates of impulse traffic in dopaminergic neurons (neuronal ‘activity’) were compared in rats on the second day of diestrus and in 12-day postpartum lactating rats that were either suckled or were nonsuckled (pup-deprived). Indices of the activities of tuberoinfundibular, tuberohypophyseal and nigrostriatal dopamine (DA) neurons were obtained by measuring the α-methyltyrosine-induced decline of DA concentrations, and the accumulation of dihydroxyphenylalanine (dopa) after the administration of an inhibitor of aromatic L-amino-acid decarboxylase in the median eminence, posterior pituitary and striatum, respectively. Biochemical indices of tuberoinfundibular DA neuronal activity and the content of DA in the anterior pituitary gland were lower in pup-deprived lactating rats than in diestrous controls, and were further reduced by suckling. These changes appeared to be specific for tuberoinfundibular DA neurons since biochemical estimates of tuberohypophyseal and nigrostriatal DA neuronal activity were the same in all three groups of animals. Following pup removal serum prolactin concentrations in the dam decreased to basal levels within 4 h and remained low for at least 72 h. The rate of dopa accumulation in the median eminence of lactating rats increased 4 h after pup removal, but remained significantly lower than diestrous values for 72 h. These results indicate that an acute suckling stimulus activates a neuronal circuit which causes a prompt decrease in tuberoinfundibular DA neuronal activity. This decrease may play a role in the suckling-induced increase in prolactin secretion. Independent of these acute changes, the ‘basal’ activity of tuberoinfundibular DA neurons is reduced in lactating rats. This decrease appears to result from the lack of responsiveness of these neurons to the stimulating actions of prolactin. This is supported by the fact that the rate of dopa accumulation in the median eminence was increased in diestrous animals 12 h after the intracerebroventricular injection of prolactin or 16 h after the administration of haloperidol (which increases serum prolactin concentrations) but these treatments were without effect in lactating animals. The decreased responsiveness of tuberoinfundibular DA neurons in lactating rats to prolactin may contribute to the ability of the anterior pituitary gland in these animals to maintain a high secretion rate of this hormone.

          Related collections

          Author and article information

          S. Karger AG
          26 March 2008
          : 36
          : 2
          : 130-137
          Departments of Pharmacology and Toxicology and Physiology, Michigan State University, East Lansing, Mich., USA
          123449 Neuroendocrinology 1983;36:130–137
          © 1983 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: 8
          Original Paper


          Comment on this article