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GABA-ergic control of α-Melanocyte-Stimulating Hormone (α-MSH) release by frog neurointermediate lobe in vitro
| Content Provider | Semantic Scholar |
|---|---|
| Author | Adjeround, S. Tonon, Marie Christine Lamacz, Marek Leneveu, E. Vaudry, Hubert |
| Copyright Year | 1986 |
| Abstract | Abstract Measurement of glutamate decarboxylase (GAD) activity in the intermediate lobe of the frog pituitary and brain showed that neurointermediate lobe extracts represented 12% of the GAD activity detected in the whole brain. No significant activity was measured in distal lobe extracts. Immunocytochemical studies revealed GAD-containing fibers among the parenchyma! cells of the pars intermedia. The localization of GAD-like material in the intermediate lobe of the frog pituitary suggested a possible role of γ-aminobutyric acid (GABA) in the regulation of melanotropic cell secretion. Administration of GAB A (10 −6 to 10 −4 M), to perifused neurointermediate lobes caused a brief stimulation of alpha-melanocyte stimulating hormone (α-MSH) release followed by an inhibition. Picrotoxin (10 −4 M), a Cl − channel blocker, abolished only the stimulatory effect of GAB A (10 −4 M), whereas bicuculline (10 −4 M), a specific antagonist of GABA A receptors, totally inhibited the effects of GABA (both stimulatory and inhibitory phases). Bicuculline induced by itself a slight stimulation of α-MSH release, suggesting that GABA-ergic nerve fibers present in the intermediate lobe are functionally active in vitro . The GABA A agonist muscimol (10 −7 to 10 −4 M) mimicked the biphasic effect of GABA on α-MSH release. Administration of baclofen, a specific GABA B B agonist (10 −7 to 10 −4 M) induced a dose-dependent inhibition of α-MSH secretion. In contrast to GABA or muscimol, baclofen did not cause any stimulatory effect whatever the dose. Taken together these result suggested that GABA A and GABa b receptors were present on frog melanotrophs. Since bicuculline totally inhibited GABA effects (stimulation and inhibition) on α-MSH release, it appears however that the effect of GABA is mainly achieved through activation of G AB A A receptors. |
| Starting Page | 717 |
| Ending Page | 723 |
| Page Count | 7 |
| File Format | PDF HTM / HTML |
| DOI | 10.1016/0361-9230(86)90206-6 |
| Volume Number | 17 |
| Alternate Webpage(s) | https://api.elsevier.com/content/article/pii/0361923086902066 |
| Alternate Webpage(s) | https://www.sciencedirect.com/science/article/pii/0361923086902066?dgcid=api_sd_search-api-endpoint |
| Alternate Webpage(s) | https://doi.org/10.1016/0361-9230%2886%2990206-6 |
| Journal | Brain Research Bulletin |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
