High- and Low-Affinity Binding Components for [3H]Imipramine in Rat Cerebral Cortex

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Abstract
The present study demonstrates that [3H]imipramine binds to both high- and low-affinity imip-ramine binding components on membranes prepared from rat cerebral cortex. Scatchard and computer analyses of saturation experiments using a wide range of [3H]imipramine concentrations (0.5 nM-50 nM) revealed the presence of two binding components. Inhibition experiments in which membranes were incubated with [3H]imipramine and various concentrations of unlabelled imipramine gave shallow inhibition curves with a Hill coefficient of 0.60 ± 0.04. When dissociation rates of imipramine were studied, biphasic dissociation curves were obtained with apparent half-times of dissociation of 2.5 ± 0.4 min and 18.5 ± 2.5 min. Thus analysis of saturation, competition, and dissociation experiments indicate that [3H]imipramine binds to low as well as high-affinity binding sites in rat cortex.