Cardiovascular activity of Micrurus lemniscatus lemniscatus (South American coralsnake) venom

Abstract

Envenomation by coralsnakes (Micrurus spp.) is characterized by blockade of peripheral neurotransmission mediated by the presence of and -neurotoxins. However, little is known about their cardiovascular activity. Micrurus lemniscatus lemniscatus is a coralsnake found in the Amazon basin and occasionally causes envenomation in humans. In this study, we examined the hemodynamic, vascular and atrial responses to M. l. lemniscatus venom.Anesthetized rats were used for hemodynamic and electrocardiogram (ECG) recordings; in vitro experiments were carried out in rat isolated thoracic aorta and atria preparations. In vivo, venom (0.1 and 0.3 mg/kg) caused immediate and persistent hypotension that was maximal within the first minute with both doses being lethal after ~40 and ~20 min, respectively. ECG, heart and respiratory rates were not altered during the transient hypotension phase induced by venom but all altered prior to death. There was no evidence of myonecrosis in cardiac muscle tissue, pulmonary hemorrhage nor thrombosis in anesthetized rats exposed to venom. In vitro, venom (10 g/ml) did not contract aortic strips nor affected the maximal responses to precontraction with phenylephrine (PE, 0.0001-30 M) in strips with and without endothelium.However, venom (10 g/ml) relaxed aortic strips with endothelium pre-contracted with PE. In aortic strips pre-contracted with PE, venom prevented acetylcholine (0.0001-30 M)-induced relaxation in strips with endothelium without affecting relaxation induced by sodium nitroprusside (0.1-100 nM) in strips without endothelium. Venom (30 g/ml) produced a transient increase of atrial contractile force without affecting atrial rate. Taken together these findings indicate a predominantly vascular action of the venom, most likely involving toxins interacting with muscarinic receptors.

Effects of the Heterodimeric Neurotoxic Phospholipase A2 from the Venom of Vipera nikolskii on the Contractility of Rat Papillary Muscles and Thoracic Aortas

“…Although the venoms of snakes from other genera contain no cardiotoxins [ 5 , 6 , 7 ], they disturb the function of the heart and blood vessels. Thus, the venom of the coral snake Micrurus lemniscatus lemniscatus caused the relaxation of endothelium-intact aortic strips preconstricted with phenylephrine and a transient increase in the contractile force of the atria without affecting the frequency of their contractions [ 8 ]. The relaxation of preconstricted aortas was observed after the application of the venoms from Montivipera bornmuelleri [ 9 ] and Lachesis acrochorda [ 10 ], with the effect being concentration-dependent.…”

“…Thus, snake venoms produce cardiovascular effects [ 8 , 9 , 10 ], and PLA 2 s are among the toxins responsible for this activity. In the venoms of snakes, PLA 2 s are some of the main components and manifest various pharmacological effects [ 16 ], including, but not limited to, neurotoxic, myotoxic, hemolytic, anticoagulant, and cytotoxic activities.…”