| 摘 要： | Tetrahydropalmatine (THP) has two enantiomers with different effects on the brain dopaminergic system. Using ~3H]spiperone for DA receptor binding assay, it was found that l-THP had an affinity to DA receptors (K_1=0.2μM). Neither d-THP nor reserpine showed such an effect even at concentrations higher than 100 or 1000μM. Based on the fact that the presynaptic DA receptors take part in feed-back regulation on tyrosiue hydroxylase activity, DOPA accumulation could be observed in rat striatum after injection of benserazide. A small dose of l-THP (2.5, 5, 10 mg/kg, ip.) caused an elevation of DOPA level by 49—282% versus the control value, and could reverse the decrease of DOPA level induced by apomorphine, a DA receptor agonist. On the contrary, d-THP displayed a biphasic effect on DOPA level, slight decrement (26—37%) at 10 and 25mg/kg, naught at 50mg/kg, and a 91% increment at 100 mk/kg, which was less than that of l-THP at 5mg/kg. Moreover, measured by pulse voltammetry, DOPAC level in the striatum
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