Effect of whole and fractionated cobra venom on sympathetic ganglionic transmission

The effect of cobra (Naja naja atra) venom and its components on ganglionic transmission was studied in vivo (the superior cervical ganglion of the cat) and in vitro (the hypogastric nerve-vas deferens preparation of the guinea-pig). Cobra venom applied directly to the ganglion, produced complete ganglionic blockade after a transient phase of stimulation. This effect was caused by its cardiotoxin but not by cobra neurotoxin or phospholipase A. Since cardiotoxin has been found to cause irreversible depolarization of the cell membrane, it was concluded that its ganglionic stimulating and blocking action was due to non-specific persistent depolarization of the ganglion cells. In vitro experiments revealed that cardiotoxin in higher concentrations first affected ganglionic transmission, then possibly postganglionic neuroeffector junction, and finally the smooth muscle itself.