2854274

GABAA receptor sites modulating catecholamine secretion in the rat adrenal gland: evidence from 3H-muscimol autoradiography and in vivo functional studies.

Article date: 1988/1/1

PubMed ID: 2854274

Journal name: Pharmacology (ISSN: 0031-7012)

ABSTRACT

The occurrence and distribution of specific 3H-muscimol binding sites, most probably identical with A type gamma-aminobutyric acid (GABA) receptors, were studied in sections of the rat adrenal gland by light microscope autoradiography. Specific binding was found primarily in the adrenal medulla, in association with chromaffin cells. A limited number of binding sites was also observed within the adrenal cortex. In urethane-anaesthetized hexamethonium-pretreated rats, intravenous GABA produced a set of 'excitatory' cardiovascular effects (increase in heart rate, force of contraction and blood pressure) which were mimicked by intravenous muscimol but not by intravenous baclofen, and were antagonized by pretreatment with bicuculline. The cardiovascular excitatory effects of intravenous GABA were unaffected by reserpine pretreatment, markedly reduced by administration of phentolamine plus propranolol, and almost completely abolished by adrenalectomy. Our findings indicate the presence of GABA receptor sites on adrenal chromaffin cells, whose excitation can produce changes in cardiovascular function.

Author List: Amenta F, Collier W L, Erdö S L, Giuliani S, Maggi C A, Meli A

Publication Types: Journal Article; Research Support, Non-U.S. Gov't

Substances mentioned in the article: Catecholamines; Receptors, GABA-A; Muscimol;

Mesh terms: Adrenal Cortex/anatomy & histology; Adrenal Glands/anatomy & histology; Adrenal Medulla/anatomy & histology; Animals; Autoradiography; Blood Pressure/drug effects; Catecholamines/secretion; Dose-Response Relationship, Drug; In Vitro Techniques; Male; Muscimol; Myocardial Contraction/drug effects; Rats; Rats, Inbred Strains; Receptors, GABA-A/metabolism;

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