Endocrinology, Vol 120, 1576-1580, Copyright © 1987 by Endocrine Society

ARTICLES

gamma-Aminobutyric acid antagonists stimulate vasopressin release from organ-cultured hypothalamo-neurohypophyseal explants

CD Sladek and WE Armstrong

gamma-Aminobutyric acid (GABA) has been identified in axon terminals innervating neurons of the supraoptic nucleus and has been shown to inhibit the electrical activity of supraoptic neurons when applied iontophoretically. This study examines the effects of GABA and GABA antagonists on vasopressin (VP) release from organ-cultured explants of the hypothalamo-neurohypophyseal system (HNS). The GABA antagonists bicuculline and picrotoxin stimulated VP release in a concentration- dependent manner. These observations suggest that VP release by HNS explants is tonically inhibited by GABA. Exposure of HNS explants to GABA (10(-8)-10(-3) M) did not consistently alter basal VP release. This was true even when penicillin, which can block GABA-activated chloride channels, was omitted from the medium. Similarly, nipecotic acid, an agent that potentiates GABA activity by inhibiting GABA uptake, did not alter basal VP release; stimulation of VP release by acetylcholine and increases in osmolality was not diminished by the addition of 10(-5) M GABA. The failure of exogenous GABA to modify basal and stimulated VP release suggests that GABAergic inhibition of VP release is maximally activated by endogenously released GABA in cultured HNS explants. This is consistent with evidence for a local source of GABA in the supraoptic nucleus and suggests that one role of GABA in the regulation of VP release is that of a potent local inhibitory neurotransmitter.

This article has been cited by other articles:

				Z. Song, S. Vijayaraghavan, and C. D. Sladek Simultaneous exposure to ATP and phenylephrine induces a sustained elevation in the intracellular calcium concentration in supraoptic neurons Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2006; 291(1): R37 - R45. [Abstract] [Full Text] [PDF]

				H. E. Howe, S. J. Somponpun, and C. D. Sladek Role of Neurokinin 3 Receptors in Supraoptic Vasopressin and Oxytocin Neurons J. Neurosci., November 10, 2004; 24(45): 10103 - 10110. [Abstract] [Full Text] [PDF]

				N. Hussy, V. Bres, M. Rochette, A. Duvoid, G. Alonso, G. Dayanithi, and F. C. Moos Osmoregulation of Vasopressin Secretion via Activation of Neurohypophysial Nerve Terminals Glycine Receptors by Glial Taurine J. Neurosci., September 15, 2001; 21(18): 7110 - 7116. [Abstract] [Full Text] [PDF]

				D. J. Morsette, H. Sidorowicz, and C. D. Sladek Role of metabotropic glutamate receptors in vasopressin and oxytocin release Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2001; 281(2): R452 - R458. [Abstract] [Full Text] [PDF]

				D. J. Morsette, H. Sidorowicz, and C. D. Sladek Role of non-NMDA receptors in vasopressin and oxytocin release from rat hypothalamo-neurohypophysial explants Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2001; 280(2): R313 - R322. [Abstract] [Full Text] [PDF]

				J. R. Kapoor and C. D. Sladek Purinergic and Adrenergic Agonists Synergize in Stimulating Vasopressin and Oxytocin Release J. Neurosci., December 1, 2000; 20(23): 8868 - 8875. [Abstract] [Full Text] [PDF]

				B. M. Kudielka, J. Hellhammer, D. H. Hellhammer, O. T. Wolf, K.-M. Pirke, E. Varadi, J. Pilz, and C. Kirschbaum Sex Differences in Endocrine and Psychological Responses to Psychosocial Stress in Healthy Elderly Subjects and the Impact of a 2-Week Dehydroepiandrosterone Treatment J. Clin. Endocrinol. Metab., May 1, 1998; 83(5): 1756 - 1761. [Abstract] [Full Text]