Abstract
Endothelium is the main source of catecholamine release in the electrical-field stimulation (EFS)–induced aortic contractions of the non- venomous snake Panterophis guttatus. However, adrenergic vasomotor control in venomous snakes such as Crotalus durissus terrificus and Bothrops jararaca has not yet been investigated. Crotalus and Bothrops aortic rings were mounted in an organ bath system. EFS-induced aortae contractions were performed in the presence and absence of guanethidine (30 μM), phentolamine (10 μM) or tetrodotoxin (1 μM). Frequency-induced contractions were also performed in aortae with endothelium removed. Immunohistochemical localization of both tyrosine hydroxylase (TH) and S-100 protein in snake aortic rings and brains, as well as in human tissue (paraganglioma tumour) were carried out. EFS (4 to 16 Hz) induced frequency-dependent aortic contractions in both Crotalus and Bothrops. The EFS-induced contractions were significantly reduced in the presence of either guanethidine or phentolamine in both snakes (p<0.05), whereas tetrodotoxin had no effect in either. Removal of the endothelium abolished the EFS-induced contractions in both snakes aortae (p<0.05). Immunohistochemistry revealed TH localization in endothelium of both snake aortae and human vessels. Nerve fibers were not observed in either snake aortae. In contrast, both TH and S100 protein were observed in snake brains and human tissue. Vascular endothelium is the main source of catecholamine release in EFS-induced contractions in Crotalus and Bothrops aortae. Human endothelial cells also expressed TH, indicating that endothelium- derived catecholamines possibly occur in mammalian vessels.
Highlights
Electrical field-induced contractions of isolated aorta of the non-venomous snake Panterophis gutattus is insensitive to the voltage-gated sodium channel blocker tetrodotoxin [1], inhibited by adrenergic receptor antagonists and abolished by removal of the endothelium [2]
We investigated whether aortae from venomous snakes such as Crotalus durissus terrificus and Bothrops jararaca would present similar behaviour following electrical-field stimulation (EFS)
Removal of the endothelium abolished the EFS-induced contraction of both aortae (Fig 4A and 4B) (n = 3) (p < 0.05)
Summary
Electrical field-induced contractions of isolated aorta of the non-venomous snake Panterophis gutattus is insensitive to the voltage-gated sodium channel blocker tetrodotoxin [1], inhibited by adrenergic receptor antagonists and abolished by removal of the endothelium [2]. These findings indicate that the endothelium as the potential source for the catecholamines in response to EFS. We investigated whether aortae from venomous snakes such as Crotalus durissus terrificus and Bothrops jararaca would present similar behaviour following EFS. The presence of tyrosine hydroxylase was assessed by immunohistochemistry in the endothelium of both snake aortae and mammalian (human) vessels
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