Association of [3H]-Imipramine and [3H]-Paroxetine Binding with the 5Ht Transporter in Brain and Platelets Relevance to Studies in Depression

Abstract

[³H]-Imipramine and [³H]-paroxetine label with high affinity a site which is associated with the serotonergic transporter in brain and platelets. The pharmacological profile of inhibition by drugs of [³H]-imipramine and [³H]-paroxetine binding is highly correlated with the potency of the drugs to inhibit the uptake of 5HT. Denervation of serotonergic neurons by electrolytic lesions or with 5,7-dihydroxytryptamine produces marked decreases in the density of [³H]-imipramine as well as [³H]-paroxetine binding. Dissociation kinetic experiments support the view that the substrate recognition site for 5HT is different from the modulatory site which is labelled by [³H]-imipramine or [³H]-paroxetine. The existence of an endogenous ligand acting on the [³H]-imipramine recognition site to modulate the 5HT transporter was proposed by several laboratories.