The nature of the stimulatory action of gamma-aminobutyric acid in the isolated perfused dog adrenals.
The effect of gamma-aminobutyric acid (GABA) on catecholamine (CA) release from adrenal medulla was investigated. GABA and GABA agonists, 3-amino-1-propane-sulfonic acid and imidazole-4-acetic acid caused CA release from isolated perfused dog adrenals in a dose-dependent manner, and no tachyphylaxis to GABA was observed. CA release elicited by GABA was antagonized by bicuculline and picrotoxin. This antagonism was specific for GABA- and GABA agonist-induced responses, response to acetylcholine being unaffected. Pretreatment with atropine plus hexamethonium did not affect the response to GABA. GABA-induced CA release was abolished by the removal of Ca2+ from perfusion medium, but not by the removal of Na+ or Cl-. Verapamil, CoCl2 and dibucaine blocked the effect of GABA. A Na+ channel blocker, tetrodotoxin did not reduce GABA-evoked CA release. These results suggest that GABA may interact with its receptor to evoke CA release from adrenal medulla in a fashion of Ca2+-dependence and independence on external Na+ or Cl-.
D000109:Acetylcholine / Q000494:pharmacology; D000311:Adrenal Glands / Q000187:drug effects*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002395:Catecholamines / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D003992:Dibucaine / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006584:Hexamethonium Compounds / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010852:Picrotoxin / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
D000109:Acetylcholine; D001285:Atropine; D001640:Bicuculline; D002118:Calcium; D002395:Catecholamines; D003035:Cobalt; D003992:Dibucaine; D006584:Hexamethonium Compounds; D010852:Picrotoxin; D013779:Tetrodotoxin; D014700:Verapamil; D005680:gamma-Aminobutyric Acid; C018021:cobaltous chloride