Weak neurotoxin from Naja kaouthia cobra venom affects haemodynamic regulation by acting on acetylcholine receptors

Recent in vitro studies of weak neurotoxins from snake venoms have demonstrated their ability to interact with both muscle-type and neuronal α7 nicotinic acetylcholine receptors (nAChR). However, the biological activity in vivo of weak neurotoxins remains largely unknown. We have studied the influence of weak neurotoxin (WTX) from the venom of cobra Naja kaouthia on arterial blood pressure (BP) and heart rate (HR) in rats and mice. It was found that intravenous injection of WTX induced a dose-dependent decrease in BP and an increase in HR in both species, the rats being more sensitive to WTX. Application of WTX following blockade of nAChRs or muscarinic acetylcholine receptors (mAChR) by hexamethonium or atropine, respectively, showed that both nAChRs and mAChRs are involved in the haemodynamic effects of WTX. Blockade of either nAChRs or mAChRs affected WTX action differently in rats and mice, thus reflecting interspecies differences in haemodynamic regulation.