REDUCTION OF SUBSTANCE-P AFTER CHRONIC ANTIDEPRESSANTS TREATMENT IN THE STRIATUM, SUBSTANTIA-NIGRA AND AMYGDALA OF THE RAT

We investigated the effects of chronic treatment with food containing one of five antidepressants on substance P(SP) content in the rat brai n using radioimmunoassay and enzyme-immunoassay. The antidepressants u sed were imipramine, desipramine, clomipramine, amoxapine and mianseri n. Following 40 days of treatment, all the antidepressants decreased S P concentrations in the striatum, substantia nigra and amygdala. Only imipramine and desipramine reduced the peptide content in the hippocam pus, and only mianserin reduced it in the septum. We further examined the acute effects of antidepressants one hour after a single intraperi toneal administration. Acute imipramine and desipramine treatment redu ced SP in the striatum, whereas acute mianserin decreased it in the st riatum and substantia nigra. These results demonstrate that all antide pressants on chronic treatment had a common effect, a reduction of SP content in the striatum, substantia nigra and amygdala. This raises th e possibility that such a decrease may contribute to the therapeutic a ction of antidepressants in affective disorders.