ENHANCEMENT OF (-)-STEPHOLIDINE ON PROTEIN-PHOSPHORYLATION OF A DOPAMINE-REGULATED AND CAMP-REGULATED PHOSPHOPROTEIN IN DENERVATED STRIATUMOF OXIDOPAMINE-LESIONED RATS

AIM: To study effects of (-)-stepholidine (SPD) on the phosphorylation of a dopamine- and cAMP-regulated phosphoprotein (DARPP-32) in the st riatum of oxidopamine-lesioned rats. METHODS: The The mount of dephosp ho-DARPP-32 was measured by a back-phosphorylation assay. RESULTS: In the striatum of control rats, SPD per se had no effect on the phosphor ylation of DARPP-32, but it antagonized the decrease by 28% of dephosp ho-DARPP-32 induced by the D-1 agonist SK&F-38393. In the denervated s triatum of phosphorylation in the denervated striatum oxidopamine-lesi oned rats, but it acts as a antagonist in normal striatum.oxidopamine- lesioned rats, SPD decreased the amount of dephospho-DARPP-32 by 44%. The effect of SPD was completely counteracted by the concomitant admin istration of the D-1 antagonist Sch-23390. CONCLUSION: SPD exhibits D- 1 agonistic action of DARPP-32 phosphorylation in the denervated stria tum oxidopamine-lesioned rats, but it acts as a antagonist in normal s triatum.