Histrionicotoxin: Effects on Some Central and Peripheral Excitable Cells

Studies on the rat diaphragm confirmed previous reports that histrionicotoxin (HTX) reversibly blocks contractions, miniature end-plate potentials and depolarizations by ACh. Microiontophoretic applications of HTX in anaesthetized cats reversibly blocked spontaneous and glutamate-evoked discharges of spinal and cortical neurones, and strongly depressed responses of Renshaw cells to ACh or ventral root stimulation. HTX blocked the excitation of cholinoceptive cortical neurones by ACh or glutamate, and concomitantly reduced spike amplitudes. The similarity between effects of HTX and procaine may indicate a common mechanism of action.