Abstract
Dopamine (DA) and fencamfamine (FCF) modulatory action on Na,K-ATPase and Mg-ATPase activity were evaluated in rat striatum. DA and FCF induced a decrease in Na,K-ATPase, without affecting Mg-ATPase activity. The effect of FCF was dose-dependent from 10 to 100 microM, with an IC50 of 4.7 x 10(-5) M. Furthermore, the effect of FCF (100 microM) increasing AMPc levels, but not GMPc, was nonadditive with that of DA (10 microM), which is consistent to a common site of action. The 8-bromo-cyclic AMP also induced a specific reduction in the Na,K-ATPase activity. The reduction of Na,K-ATPase induced by FCF (100 microM) was blocked by either SCH 23390 or sulpiride, which are D1 and D2 receptor antagonists. The decrease in striatal NA,K-ATPase activity induced by FCF was blocked by KT 5720, a selective inhibitor of cyclic AMP-dependent protein kinase (PKA), but not by KT 5823, a selective inhibitor of cyclic GMP-dependent protein kinase (PKG). Otherwise, KT 5720 or KT 5823 did not produce any change in Na,K-ATPase or Mg-ATPase activity. These data suggest that FCF reduces Na,K-ATPase activity through cyclic AMP-dependent changes in protein phosphorylation via a PKA mechanism.