Anticonvulsant effect of water extract of Scutellariae radix in mice

Since a previous study indicated that the water extract of Scutellariae radix (SR) had high affinity for the benzodiazepine (BDZ) binding site of GABA(A), receptors, the present study examined whether SR water extract has an anticonvulsant effect in vivo and an enhancing effect on gamma -amino-n-butyric acid (GABA)-stimulated uptake of Cl-36(-) in cortex preparation in vitro in mice. The results showed that SR water extract had little effect on pentylenetetrazol (PTZ, 85 mg/kg, s.c.)-induced clonic seizures but significantly inhibited maximal electroshock-induced tonic seizures with an ED50 of 3.6 g/kg. The BDZ agonist chlordiazepoxide (10 mg/kg, i.p.) had anticonvulsant activity on both types of seizures. In Cl-36(-) uptake assay, SR water extract (1-500 mug/ml) had no significant effect on 25 muM GABA-stimulated Cl-36(-) uptake, whereas chlordiazepoxide (10 muM) increased the Cl-36(-) uptake to 125% of control. Therefore, the present results showed for the first time that SR water extract had anticonvulsant activity against maximal electroshock-induced tonic seizures, and suggested that this anticonvulsant effect might be not via the activation of the BDZ binding site of GABA(A) receptors, but probably via the prevention of seizure spread. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.