DL-Tetrahydropalmatine (THP), an active component isolated from corydalis (a Chinese herbal medicine), possesses analgesic effects. Systemic administration of picrotoxin (3-4 mg/kg) produced increases of locomotion (including horizontal motion, vertical motion, and total distance traveled), elevations of turnings (including both clockwise and anticlockwise), and inhibition of postural freezing in freely moving rats, and increases of amygdaloidal release of dopamine in anesthetizes rats. All the afore-mentioned activity measures induced by picrotoxin were suppressed following THP pretreatment. The results indicate that THP may act through inhibition of amygdaloid dopamine release to inhibit an epileptic attack.
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