EFFECTS OF DL-TETRAHYDROPALMATINE ON ACTION POTENTIALS AND CONTRACTILITIES OF GIUNEA PIG PAPILLARY MUSCLES AND ITS LOCAL ANESTHETIC ACTION
Zhao Dongke, et al (Department of Pharmacology)
The effects of DL-tetrahydropalmatine (THP)on action potentials and contractilies of isolated giunea pig papillary muscle cells were observed with the microelecorode technique. THP(10~(-5)-3x10~(-4)M)could produce a dose-dependent negative inotropic effect. THP(0.1 mM)could shorten APD_(20) and APD_(50) evidently (p0.01), prolong APD_(90) and ERP, and decrease RP. The effects of THP on APA and Vmax were smaller. This showed excitationcontraction uncoupling. The intradermic injection of THP could allenuate local stimulated pain in guinea pigs. Also ,THP could decrease the action potential amplitude of isolated sciatic nerves in toads, indicating that THP possesses a local anesthetic action, weaker than that produced by quindine. The results show that THP inhibits not only the influx of calcium, but also the influx of sodium and the out flow of Potassium.