title: Ascorbate modulates 5-[3H]hydroxytryptamine binding to central 5-HT3 sites in bovine frontal cortex.
abstract: 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-[3H]hydroxytryptamine ([3H]5-HT) binding to bovine frontal cortex membranes. Under conditions where [3H]5-HT binding is reversible and saturable, ascorbate causes a concentration-dependent increase in the affinity of [3H]5-HT for central 5-HT3 binding sites. At pH 7.4, increasing ascorbate from 0 to 5.7 mM changes the equilibrium affinity constant (KD) of binding to 5-HT3 sites from 125 nM to 30 nM, without affecting binding site number. These ascorbate-induced effects are pH dependent. At pH 7.1 binding to central 5-HT3 sites is essentially eliminated in the presence of ascorbate. These studies suggest that ascorbate and hydrogen ion concentration interactions may modulate serotonergic function.
authors: Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri 63110.
authors: R D
authors: RD
authors: Todd
authors: P A
authors: PA
authors: Bauer
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*
chemical_list: D011985:Receptors, Serotonin; D012701:Serotonin; D001205:Ascorbic Acid