Antidepressant-like effects of a methanol extract of Leonotis nepetifolia in mice

This study evaluated the antidepressant-like effects of a methanol extract of Leonotis nepetifolia in behavioural tests in mice. Our results showed that a single administration of the extract significantly reduced immobility behaviour in the tail suspension test, while three administrations were necessary to diminish immobility behaviour in the forced swimming test. A daily dose of the extract for 28 days improved body weight gain and significantly reduced corticosterone levels of mice exposed to chronic unpredictable mild stress. Metabolic profiling of the extract revealed that nepetaefolin, methoxynepataefolin, and 7-O-β-glucoside luteolin were the main products. Acute and repeated administration of the extract produced antidepressant-like effects in animals subjected to chronic stress. Our results suggest the hypothalamus-hypophysis-adrenal axis participates in the antidepressant actions of the extract. These results show that alterations in behaviour elicited by stress can be prevented with L. nepetifolia treatment.