Molecular and Physiological Evidence for Functional γ-Aminobutyric Acid (GABA)-C Receptors in Growth Hormone-secreting Cells

The neurotransmitter γ-aminobutyric acid (GABA), released by hypothalamic neurons as well as by growth hormone- (GH) and adrenocorticotropin-producing cells, is a regulator of pituitary endocrine functions. Different classes of GABA receptors may be involved. In this study, we report that GH cells,...

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Bibliographic Details
Published in:The Journal of biological chemistry 2003-05, Vol.278 (22), p.20192-20195
Main Authors: Gamel-Didelon, Katia, Kunz, Lars, Föhr, Karl Josef, Gratzl, Manfred, Mayerhofer, Artur
Format: Article
Language:English
Subjects:
Animals
Base Sequence
Calcium - metabolism
Cell Line
DNA Primers
Growth Hormone - metabolism
Immunohistochemistry
Patch-Clamp Techniques
Pituitary Gland - cytology
Pituitary Gland - metabolism
Rats
Rats, Sprague-Dawley
Receptors, GABA - metabolism
Receptors, GABA - physiology
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Summary:The neurotransmitter γ-aminobutyric acid (GABA), released by hypothalamic neurons as well as by growth hormone- (GH) and adrenocorticotropin-producing cells, is a regulator of pituitary endocrine functions. Different classes of GABA receptors may be involved. In this study, we report that GH cells, isolated by laser microdissection from rat pituitary slices, possess the GABA-C receptor subunit ρ2. We also demonstrate that in the GH adenoma cell line, GH3, GABA-C receptor subunits are not only expressed but also form functional channels. GABA-induced Cl- currents were recorded using the whole cell patch clamp technique; these currents were insensitive to bicuculline (a GABA-A antagonist) but could be induced by the GABA-C agonist cis-4-aminocrotonic acid. In contrast to typical GABA-C mediated currents in neurons, they quickly desensitized. Ca2+i recordings were also performed on GH3 cells. The application of either GABA or cis-4-aminocrotonic acid led to Ca2+ transients of similar amplitude, indicating that the activation of GABA-C receptors in GH3 cells may cause membrane depolarization, opening of voltage-gated Ca2+ channels, and a subsequent Ca2+ influx. Our results point at a role for GABA in pituitary GH cells and disclose an additional pathway to the one known via GABA-B receptors.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M301729200