Original Articles

Effect of tetrahydroberberine on blockade of pre- and postsynaptic dopamine receptors (author's transl)

Authors: Xiao-li Wang, Guo-zhang Jin, Lei-ping Yu, Jian-hua Li

Abstract

THB 45 mg/kg (ip) to rat antagonized the stereotyped behavior induced by sc apomorphine 5 mg/kg. The hyperactivity and stereotyped behavior were induced by ip l-dopa 100 mg/kg in combination with ip benserazide 300 mg/kg and deprenyl 10 mg/kg. THB had the same antagonistic response to l-dopa as to apomorphine. These results showed that THB blocked the function of postsynaptic DA receptor.
After ip THB 100 or 150 mg/kg in rat, homovanillic acid level in corpus striatum was elevated from the control value (229±40 ng/g tissue) to 675±105 and 813±90 ng/g,respectively.
THB 15, 30, 70 or 100 mg/kg ip increased the concentration of l-dopa in rat corpus striatum 250-400%. This enhancement was antagonized by ip apomorphine 5 mg/kg. The accumulation of l-dopa in corpus striatum evoked by ip γ-butyro-lactone 600 mg/kg was abolished completely by apomorphine, and ip THB 70 mg/kg reversed this depression by apomorphine. So there was an antagonistic effect on DA receptor between THB and apomorphine. These results indicated that THB enhanced the activity of tyrosine hydroxylase through a feed-back mechanism in blocking the presynaptic DA receptor, just as haloperidol did.
It is suggested that THB is a blocking agent of DA receptor.
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