Effects of Hypericum perforatum on levels of 5-hydroxytryptamine, noradrenaline and dopamine in the cortex, diencephalon and brainstem of the rat

The plant Hypericum perforatum is used in folk medicine to treat several di seases and research attention has been recently focused on its antidepressa nt action. Hypericin and flavonoids are the most important constituents of the plant, but the exact role of these compounds in the effects of hypericu m on mood disorders is not well known. We have investigated the contributio n of these compounds to the antidepressant effects of hypericum. The effects of acute administration of hypericum extracts on levels of 5-hy droxytryptamine (5-HT), tryptophan, 5-hydroxyindoleacetic acid (5-HIAA), no radrenaline and dopamine in the cortex, diencephalon and brainstem was eval uated. The levels of these neurotransmitters were measured 1 h and 24 h aft er administration of two different extracts, one containing 0.3% hypericin and 6% flavonoids (Li 160; 25-500 mg kg(-1)), the other containing 0.3% hyp ericin and 50% flavonoids (Ph-50; 25-500 mg kg(-1)) Results from experiment s performed on 5-HT turnover were compared with the effects of fluoxetine ( 10-80 mg kg(-1)). Li 160, Ph-50 and fluoxetine induced a significant increa se in the 5-HT content of the cortex. In the diencephalon Ph-50, but not Li 160 or fluoxetine, elicited an increase in 5-HT and 5-HIAA levels. In the brainstem Ph-50 and fluoxetine caused an increase in 5-HT content; Li 160 d id not change neurotransmitter content. Both Li 160 and Ph-50 caused increa ses of noradrenaline and dopamine in the diencephalon. In the brainstem onl y Ph-50 induced an increase in noradrenaline content. Our data confirm that acute administration of hypericum extracts modifies t he levels of neurotransmitters involved in the pathophysiology of mood diso rders. When the extracts contain a higher concentration of flavonoids the e ffects are more widespread and involve brain regions such as diencephalon a nd brainstem that are implicated in depression.