Sub-chronic treatment with an extract of Hypericum perforatum (St John's wort) significantly reduces cortisol and corticosterone in the rat brain.

Extracts of Hypericum perforatum (HP) have been shown to be effective for the treatment of mild to moderate depression. Its mode of action has not been fully elucidated. An increase in plasma and cerebrospinal fluid (CSF) cortisol is frequently observed in depression. Studies have suggested that HP might alter brain cortisol and corticosterone through its effect on multidrug transporter glycoprotein (Pgp). We investigated the effect of sub-chronic treatment with an extract of HP (LI 160) on brain levels of corticosterone and cortisol in the rat. Results show that HP significantly reduced corticosterone and cortisol in brain frontal cortex tissue. These changes are not reflected in serum. These findings may be important with respect to HPs mode of antidepressant action.