An acetylcholinesterase inhibitor, 3-benzidino-5-methyl-6-phenylpyridazine, blocking outward potassium currents in acutely isolated rat hippocampal pyramidal neurons

3-benzidino-5-methyl-6-phenylpyridazine (BMP) inhibited electric eel acetylcholinesterase (AChE), with IC50 being 0.58 μmol·L 1. As an AChE inhibitor, the effects of BMP on delayed rectifier potassium current (I K(DR)) and transient outward potassium current (I K(A)) in acutely isolated rat hippocampal pyramidal neurons were studied using the whole cell patch-clamp technique. BMP (0.1–50 μmol·L 1) inhibited I K(DR) and I K(A) in a concentration-dependent and voltage-independent manner. The IC50 value for the blocking action of BMP on I K(DR) and I K(A) was calculated to be 2.92 and 2.11 μmol·L 1, respectively. At the concentration of 10 μmol·L 1, BMP shifted the activation curve of IK(DR) to negative potential by 8.85 mV. Meanwhile, at the concentration of 10 μmol·L 1, BMP also shifted the activation and the steady-state inactivation curve of IK(A) to negative potential by 5.82 mV and 10.02 mV, respectively. In conclusion, BMP potently inhibits I K(DR) and I K(A) in rat hippocampal pyramidal neurons, which may contribute to restore the damaged central nervous system. Supported by National Natural Science Foundation of China (Grant No. 20637010)