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SYNTHESIS OF RADIOACTIVE ACETYLCHOLINE FROM [ 3 H]CHOLINE AND ITS RELEASE FROM CEREBRAL CORTEX SLICES IN VITRO
Author(s) -
Richter Judith A.,
Marchbanks R. M.
Publication year - 1971
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.1471-4159.1971.tb11999.x
Subject(s) - acetylcholine , choline , chemistry , cerebral cortex , levorphanol , in vitro , cortex (anatomy) , cholinergic , biophysics , biochemistry , endocrinology , biology , neuroscience , (+) naloxone , receptor , opioid
— Guinea pig cerebral cortex slices were incubated for 60 min in a medium containing [ 3 H]choline with or without the addition of 33 mM‐KCl for the last 30 min. KC1 caused the release into the medium of large amounts of both bioassayable and radioactive ACh, while at the same time their concentrations in the tissue decreased. The specific activity (d.p.m./pmol) of the ACh released by KC1 was greater than that released in control incubations, indicating that it comes from a newly synthesized, more radioactive store. The amounts of [ 3 H]choline, [ 3 H]ACh and the specific activity of tissue acetylcholine reached a plateau in the tissue 30 min after the addition of isotope. However isotopic equilibrium was not achieved because the specific activity of the ACh released, with or without KC1 in the subsequent 30 min, was less than the specific activity of the ACh remaining in the tissue. This implies the existence of a pool of ACh in the tissue which is turning over very slowly or is being synthesized from a less radioactive pool of choline. This pool of ACh does not contribute substantially to that released by KC1. Levorphanol at 10 −3 M, as well as the analgesically inactive stereoisomer, dextrorphan, blocked the KCl‐stimulated release of both bioassayable and radioactive ACh. These drugs demonstrate the coupling of synthesis and release of ACh in cerebral cortex slices.