Involvement of the central monoaminergic system in the antidepressant-like effect of catalpol in mice.

Catalpol is a natural iridoid glycoside with diverse bioactivities that is found in abundance in Rehmannia glutinosa Libosch. (Scrophulariaceae). The present study assessed whether catalpol treatment (5, 10, or 20 mg/kg for 14 days by intragastric administration (i.g.)) has an antidepressant-like effect on mice performing the forced swim test (FST), tail suspension test (TST), open field test (OFT), and tests for reversal of reserpine-induced ptosis, akinesia, and hypothermia. This study also examined the potential role that catalpol plays in the cerebral monoaminergic system. Results indicated that catalpol administration produced an antidepressant-like effect in mice, as indicated by the reduced duration of immobility in the FST and TST, but it had no effect on locomotor activity in the OFT. Catalpol treatment significantly counteracted the decrease in rectal temperature, akinesia, and eyelid ptosis induced by reserpine. Moreover, catalpol increased levels of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the brains of mice, but it did not affect levels of norepinephrine (NE) or dopamine (DA). These antidepressant-like effects of catalpol are essentially similar to the effects of the clinical antidepressant fluoxetine hydrochloride (FH). This is the first study to indicate that catalpol has an antidepressant-like effect and that its action may be mediated by the central serotonergic system, and not by noradrenergic or dopaminergic systems.