DIFFERENT EFFECTS OF ANTIDEPRESSANTS ON DISSOCIATION OF H-3 IMIPRAMINE FROM SOLUBILIZED BINDING-SITES OF RAT-BRAIN

1. The effects of several antidepressants and 5-hydroxytryptamine on dissociation of H-3-imipramine from solubilized binding sites were investigated. 2. Binding sites were solubilized from rat brain membranes and gelfiltrated on a column of Sephacryl S-300. 3. Most of the agents used allowed biphasic dissociation with 1mM of displacing agent and without using dilution-induced dissociation. This biphasic dissociation without nonspecific effects of membranes may be due to the existence of low-affinity binding sites. 4. Dissociation of up to 40 min followed first-order kinetics. The dissociation half-life of H-3-imipramine with the various displacing agents was calculated at from 15.0 to 25.0 min, and the differences among the agents were not so significant as the attenuation or the acceleration of the dissociation was indicated. The lower concentration of the displacing agents may obscure the modulation of the dissociation.