Structure‐activity Relations for the Inhibition of 5‐hydroxytryptamine Uptake by Tricyclic Antidepressants Into Synaptosomes From Serotonergic Neurones in Rat Brain Homogenates

1 The inhibitory effects of various analogues of imipramine on [(3)H]-5-hydroxytryptamine (5-HT) uptake into homogenates of rat hypothalamus were examined.2 For structures with a three carbon side chain the tertiary amine derivative was more potent than the compound with a secondary amine function.3 Potency was reduced by increasing or decreasing the length of the three carbon side chain by one carbon atom.4 Substitution of a methyl group in the alpha or beta position in the side chain reduced potency.5 Replacement of the dimethylene bridge in imipramine by a sulphur atom or substitution of a C=C double bond for the exocyclic N-C bond of imipramine both led to a fall in potency.6 3-Chlorimipramine was the most potent inhibitor of [(3)H]-5-hydroxytryptamine uptake of the compounds tested.