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4‐Aminobutyrate Can Be Released Exocytotically from Guinea‐Pig Cerebral Cortical Synaptosomes
Author(s) -
Sihra Talvinder S.,
Nicholls David G.
Publication year - 1987
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1987.tb03424.x
Subject(s) - depolarization , exocytosis , biophysics , synaptosome , guinea pig , chemistry , cytosol , endogeny , membrane potential , membrane , synaptic vesicle , biochemistry , vesicle , biology , endocrinology , enzyme
: Guinea‐pig synaptosomes possess two functional pools of 4‐aminobutyrate (GABA). One is rapidly labelled by added [ I4 C]GABA, is steadily released in a Ca 2+ ‐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 [ 14 C]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 Ca 2+ . Ca 2+ ‐independent release occurs by thermodynamic reversal of the plasma membrane uptake pathway following artifactually prolonged depolarization, whereas Ca 2+ ‐dependent release is consistent with physiological exocytosis from vesicular stores.