Central convulsive action of l-securinine

l-securinine is an alkaloid isolated from the leaves of Securinega suffruticosa. In mice, diazepam showed an antagonism to convulsion induced by l-securinine, with ip ED50 of 0.28 mg/kg, which was 3 times more potent that that of diazepam on the convulsions induced by picrotoxin and isoniazid. GABA (ip 600 mg/kg/d, 3d or icv 20 microg) antagonized the convulsion induced by picrotoxin, but not by l-securinine. Combination of GABA (icv 10 microg) and diazepam (ip 0.18 mg/kg) displayed an inhibitory effect on the convulsion induced by l-securinine, but neither of them alone did not affect the convulsion. Both ip picrotoxin 3 mg/kg and ip isoniazid 100 mg/kg manifested a synergism with l-securinine. Mecamylamine showed a n antagonism on the convulsion induced by l-securinine, with ip ED50 of 21 mg/kg, which was 88 times as much as that induced by nicotine. Reserpine 10 mg/kg ip was synergistic with l-securinine, while chlorpromazine, clonidine, 5-HTP, propranolol andyohimbine had no such synergistic effect. These results indicate that the central stimulation of l-securinine may be related to the GABA-ergic function.