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Ascorbate Modulates 5‐[ 3 H]Hydroxytryptamine Binding to Central 5‐HT 3 Sites in Bovine Frontal Cortex
Author(s) -
Todd Richard D.,
Bauer Paul A.
Publication year - 1988
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.1471-4159.1988.tb03037.x
Subject(s) - binding site , chemistry , serotonergic , biophysics , membrane , serotonin , biochemistry , receptor , biology
Ascorbate is present in millimolar concentrations in mammalian brain and can be released from cellular stores by membrane depolarization. We report here that physiologically relevant concentrations of ascorbate modulate 5‐[ 3 H]hydroxytryptamine ([ 3 H]5‐HT) binding to bovine frontal cortex membranes. Under conditions where [ 3 H]5‐HT binding is reversible and saturable, ascorbate causes a concentration‐dependent increase in the affinity of [ 3 H]5‐HT for central 5‐HT 3 binding sites. At pH 7.4, increasing ascorbate from 0 to 5.7 m M changes the equilibrium affinity constant ( K D ) of binding to 5‐HT 3 sites from 125 n M to 30 n M , without affecting binding site number. These ascorbate‐induced effects are pH dependent. At pH 7.1 binding to central 5‐HT 3 sites is essentially eliminated in the presence of ascorbate. These studies suggest that ascorbate and hydrogen ion concentration interactions may modulate serotonergic function.