4-Aminobutyrate can be released exocytotically from guinea-pig cerebral cortical synaptosomes.
Guinea-pig synaptosomes possess two functional pools of 4-aminobutyrate (GABA). One is rapidly labelled by added [14C]GABA, is steadily released in a Ca2+-independent manner when the Na+ electrochemical potential across the plasma membrane is collapsed, and is depleted by the GABA analogue 2,4-diaminobutyrate (DABA), all of which is consistent with a cytosolic location. A second, noncytosolic compartment only slowly equilibrates with exogenous [14C]GABA, is not depleted by DABA, but can release 350 pmol of endogenous GABA/mg of protein (8% of the total intrasynaptosomal GABA) within 15 s of depolarization in the presence of Ca2+. Ca2+-independent release occurs by thermodynamic reversal of the plasma membrane uptake pathway following artifactually prolonged depolarization, whereas Ca2+-dependent release is consistent with physiological exocytosis from vesicular stores.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism*; D005089:Exocytosis; D005260:Female; D006168:Guinea Pigs; D008297:Male; D013574:Synaptosomes / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005680:gamma-Aminobutyric Acid; D002118:Calcium