EFFECTS OF CARBAMAZEPINE ON NERVE ACTIVITY AND TRANSMITTER RELEASE INNEUROBLASTOMA-GLIOMA HYBRID-CELLS AND THE FROG NEUROMUSCULAR-JUNCTION

Effects of the antiepileptic drug carbamazepine on nerve action potent ial and transmitter release in mouse neuroblastoma-glioma hybrid cells (NG108-15) and the frog neuromuscular junction were studied. Carbamaz epine within a concentration range of 0.1-0.5 mmol/L reduced the peak height of the action potential of the NG108-15 cells, whereas the memb rane potential and membrane resistance were unaffected. Voltage clamp revealed that the decrease in the action potential was due to the bloc kage of the Na+, delayed K+ and transient Ca2+ currents. Carbamazepine did not affect Ca2+-activated and A type K+ currents and long-lasting Ca2+ current. In the frog neuromuscular junction, carbamazepine decre ased the mean quantal content by a parallel shift in the frequency aug mentation-potentiation (FAP) relation. It is concluded that carbamazep ine blocks the voltage-dependent Naf, delayed Kf, and transient Ca2+ c urrents and quantal transmitter release through a decrease of nerve ex citation.