Effects of a methanolic extract and a hyperforin-enriched CO2 extract of Hypericum perforatum on alcohol intake in rats

Abstract

Hypericum perforatum extracts (HPE) inhibit ethanol intake in rats. Hypericin and hyperforin have been proposed as major active principles of HPE. The present study compared the effect on ethanol intake in alcohol-preferring rats of two Hypericum perforatum extracts: a methanolic extract containing 0.3% hypericin and 3.8% hyperforin (HPE1) and a CO2 extract (HPE2) with 24.33% hyperforin and very low hypericin content. Freely feeding and drinking rats were offered 10% ethanol 2 h/day and HPE were given intragastrically 1 h before access to ethanol. Both extracts dose-dependently reduced ethanol intake, HPE2 being about eight times more potent than HPE1. Food and water intakes were not affected by doses that reduced ethanol intake. HPE2, unlike HPE1, reduced blood-alcohol levels (BAL) at doses of > or = 31.2 mg/kg, whereas the dose of 15.6 mg/kg, which reduced ethanol intake, did not significantly modify BAL; blood-acetaldehyde levels were never increased. As previously observed for HPE1, intracerebroventricular pretreatment with 5,7-dihydroxytryptamine (150 microg/rat) did not affect attenuation of ethanol intake induced by HPE2, but reduced its effect in the forced swimming test (FST). Intraperitoneal pretreatment with the sigma-1 receptor antagonist NE-100 (0.25 mg/kg) did not affect inhibition of ethanol intake induced by HPE1 (250 mg/kg) or HPE2 (125 mg/kg), but abolished the effect of both extracts in the FST. In conclusion, the present results indicate that HPE2 inhibits ethanol intake more potently than HPE1; the higher potency of HPE2 parallels the hyperforin content, suggesting that hyperforin may have an important role in reducing ethanol intake. Moreover, different neurochemical mechanisms are apparently responsible for the reduction of ethanol intake and for the antidepressant-like effect of HPE.