Enhancement by GABA of the stimulation-evoked catecholamine release from cultured bovine adrenal chromaffin cells.
The possible involvement of GABAergic mechanisms in the catecholamine (CA) release from adrenal medulla was investigated in a primary culture of bovine adrenal chromaffin cells. GABA elicited CA release and enhanced acetylcholine (ACh)-, excess K(+)- and veratridine-evoked CA release. Muscimol, a selective GABAA receptor agonist, mimicked the action of GABA on CA release. On the other hand, baclofen, a GABAB receptor agonist, failed to affect basal or evoked CA release. Furthermore, bicuculline and picrotoxin blocked the enhancement by GABA of veratridine-evoked CA release without affecting basal CA release and CA release evoked by veratridine. In Ca2(+)-free medium, GABA failed to affect basal and caffeine-evoked CA release. ACh-evoked CA release was slightly reduced by bicuculline, whereas excess K(+)-evoked CA release was not, suggesting the involvement of endogenous GABA in CA release evoked by ACh. These results suggest a facilitatory modulation by GABA of basal and evoked release of CA from bovine adrenal medulla through GABAA receptor-mediated mechanisms.
Kitayama
S
S
Department of Pharmacology, Hiroshima University School of Dentistry, Japan.
Morita
K
K
Dohi
T
T
Tsujimoto
A
A
D000109:Acetylcholine / Q000494:pharmacology; D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D002838:Chromaffin System / Q000166:cytology / Q000378:metabolism*; D058787:GABA-A Receptor Antagonists; D009118:Muscimol / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000502:physiology; D014701:Veratridine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D000109:Acetylcholine; D001640:Bicuculline; D002110:Caffeine; D002118:Calcium; D002395:Catecholamines; D058787:GABA-A Receptor Antagonists; D009118:Muscimol; D009538:Nicotine; D010852:Picrotoxin; D011188:Potassium; D011963:Receptors, GABA-A; D014701:Veratridine; D005680:gamma-Aminobutyric Acid