QX-314 blocks all Nav channels once exposed to the intracellular face of the channel protein. However, this compound can penetrate the cell interior once applied outside the cell. Via certain types of Nav channels, it can permeate and exert blocking activity via TTX sensitive channels.1 Intracellular recordings from inferior olivary neurons in brain stem slice preparation demonstrated that Na+ - dependent action potential was completely blocked for approximately five minutes after impalement with a microelectrode containing 50 mM QX-314, whereas the low-threshold Ca2+ spike was still generated.2 QX-314 is widely used to block Nav channels and used as a tool in neurophysiological recordings
