POSSIBLE ANXIOLYTIC EFFECTS OF CHRYSIN, A CENTRAL BENZODIAZEPINE RECEPTOR-LIGAND ISOLATED FROM PASSIFLORA-COERULEA

The pharmacological effects of 5,7-dihydroxyflavone (chrysin), a natur ally occurring monoflavonoid that displaces [H-3]flunitrazepam binding to the central benzodiazepine (BDZ) receptors, were examined in mice. In the elevated plus-maze test of anxiety, diazepam (DZ, 0.3-0.6 mg/k g) or chrysin (1 mg/kg) induced increases in the number of entries int o the open arms and in the time spent on the open arms, consistent wit h an anxiolytic action of both compounds. The effects of chrysin on th e elevated plus-maze was abolished by pretreatment with the specific B DZ receptor antagonist Ro 15-1788 (3 mg/kg). In the holeboard, diazepa m (1 mg/kg) and chrysin (3 mg/kg) increased the time spent head-dippin g. In contrast, high doses of DZ (6 mg/kg) but not of chrysin produced a decrease in the number of head dips and in the time spent head-dipp ing. In the horizontal wire test, diazepam (6 mg/kg) had a myorelaxant action. In contrast, chrysin (0.6-30 mg/kg) produced no effects in th is test. These data suggest that chrysin possesses anxiolytic actions without inducing sedation and muscle relaxation. We postulate that thi s natural monoflavonoid is a partial agonist of the central BDZ recept ors.