Enhancement of 3H-phenytoin binding by diazepam and (+)bicuculline |
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Authors: | M M Okazaki B K Madras K E Livingston L Spero W M Burnham |
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Institution: | 1. Department of Pharmacology University of Toronto Toronto, Canada M5S 1A8;2. Limbic Mechanisms Research Laboratory Department of Neurosurgery Wellesley Hospital Toronto, Canada M4Y 1J3 (B.K.M., K.E.L.) |
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Abstract: | 3H-Phenytoin binding to the particulate fraction of rat wholebrain homogenate was studied using the filter assay technique. It was found that diazepam and (+)bicuculline methobromide caused a concentration-dependent enhancement of the total binding of 3H-phenytoin, whereas GABA and (-)bicuculline methobromide (the inactive bicuculline isomer) had no effect. In subsequent competition experiments (labelled versus unlabelled phenytoin), it was found that the presence of a potentiating concentration of diazepam transformed the biphasic phenytoin competition isotherm into a simple curve with a Hill coefficient of approximately one, and a Ki of 110 nM. |
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