Repeated treatment with antidepressants does not modify the locomotor effect of dopaminergic stimulants injected into the rat hippocampus.

In the present study, we investigated the influence of antidepressant drugs (imipramine, amitriptyline, citalopram, mianserin) and electroconvulsive shock on the locomotor effect in rats, induced by amphetamine or quinpirole injected intrahippocampally. The antidepressant drugs were administered in a dose of 10 mg/kg p.o. twice daily for 14 days. Electroconvulsive shock was applied once daily for 10 days. Amphetamine (2.5 micrograms) or quinpirole (0.5 micrograms) were injected bilaterally into the hippocampus 2 or 72 hr after the last treatment with antidepressant drugs or electroconvulsive shock. None of the examined antidepressant drugs affected the response to either stimulant. Electroconvulsive shock potentiated the response to amphetamine but not to quinpirole. These results indicate that repeated treatment with antidepressant drugs does not modify the hippocampal dopamine system. The mechanism involved in the potentiation of the response to amphetamine following repeated electroconvulsive shock remains to be elucidated.