title: GABA induced changes in acetylcholine release from slices of guinea-pig brain.
abstract: The effect of GABA on acetylcholine (ACh) release was investigated on superfused slices of guinea-pig cerebral cortex (CC), caudate nucleus (CN), tuberculum olfactorium and brain stem. GABA (1--6 x 10(-3) mol/l) increased the spontaneous and KCl-evoked ACh overflow in CC and CN, reduced the electrically-evoked release in all areas tested (most evidently in CC and CN) and lowered the threshold of electric stimulation-induced ACh release in CC. These effects were also caused by 3-amino-1-propane sulphonic acid (1 x 10(-3) mol/l) and ethanolamine-O-sulphate (2 x 10(-3) mol/l), were reduced by bicuculline (1 x 10(-4) mol/l) and fully antagonized by picrotoxin (8 x 10(-5) mol/l), but they were not influenced by phentolamine, methysergide, spiroperidol or strychnine. Tetrodotoxin (TTX) (5 x 10(-7) mol/l) blocked the facilitation of spontaneous ACh release by GABA only when the slices were perfused with normal Krebs solution, but not when perfused with a KCl-enriched medium. These results suggest that GABA affects the cholinergic transmitter release through bicuculline- and picrotoxin-sensitive receptors, showing low affinity toward the agonist. Moreover GABA modulation of resting ACh release requires action potentials only in normal [K+]0, but not in high [K+]0, suggesting that GABA-receptive sites are located at cholinergic terminals.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D011189:Potassium Chloride / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000187:drug effects; D011963:Receptors, GABA-A; D013654:Taurine / Q000031:analogs & derivatives / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
chemical_list: D004983:Ethanolamines; D011956:Receptors, Cell Surface; D011963:Receptors, GABA-A; D013654:Taurine; D005680:gamma-Aminobutyric Acid; C001355:tramiprosate; D011189:Potassium Chloride; C020619:ethanolamine O-sulfate; D000109:Acetylcholine