Influência do controle vagal na resistência vascular pulmonar e desvio intracardíaco em Crotalus durissus (Squamata: Viperidae)
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Data
2012-11-01
Autores
Filogonio, Renato [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Em répteis não crocodilianos, o ventrículo parcialmente dividido permite que o sangue venoso pobre em oxigênio recircule no circuito sistêmico, configurando um desvio sanguíneo intracardíaco (“shunt”) da direita para a esquerda (DSIc D-E), ou que o sangue arterial rico em oxigênio retorne ao circuito pulmonar, configurando um desvio sanguíneo intracardíaco da esquerda para a direita (DSIc E-D). Teoricamente, se o DSIc apresentar alguma vantagem adaptativa, seria controlado, ao invés de uma mera consequência passiva do sistema circulatório às mudanças das resistências vasculares. O nervo vago inerva o tronco pulmonar e possui influência no controle da resistência do circuito pulmonar. Assim, o aumento ou diminuição desta resistência poderia definir a direção do desvio sanguíneo resultante. Neste estudo foi postulada a hipótese de que a ausência do tônus vagal causaria mudanças no controle do DSIc em animais submetidos a variações na temperatura e na atividade. Para tanto, foram comparados dois grupos de cascavéis, Crotalus durissus, com nervo vago intacto ou seccionado, submetidas às mesmas condições de temperatura e de atividade. Os parâmetros hemodinâmicos foram aferidos através de canulação oclusiva. De forma geral, o aumento da temperatura e da atividade aumentaram a frequência cardíaca (fH), débito cardíaco (DC), fluxo sanguíneo pulmonar (Qpul) e fluxo sanguíneo sistêmico (Qsis), embora apenas a atividade tenha feito com que as serpentes desenvolvessem um DSIc E-D como resposta ao aumento da demanda de O2 nos tecidos. A atividade também foi responsável pelo aumento das pressões arteriais média sistêmica e pulmonar. A vagotomia unilateral também causa aumento dos fluxos sanguíneos, embora não afete a fH. A ausência do controle vagal tem maior efeito no controle da resistência...
In non crocodilian reptiles, the ventricle is partially divided and allows venous blood, low in oxygen, to recirculate the systemic circuit, which is referred to as a right-to-left shunt (R-L shunt), or the oxygen-rich blood to return to the pulmonary circuit, referred to as a left-to-right shunt (L-R shunt). In theory, if intracardiac shunts provide any adaptive advantage, it would be controlled rather than be a passive consequence of changes in vascular resistances. The vagus nerve innervates the pulmonary trunk and has a role in controlling the resistance of the pulmonary circuit (Rpul). Thus, the control of Rpul could set the direction of the resulting shunt. In this study we hypothesized that the lack of vagal tone causes changes in control of intracardiac shunts in animals subjected to variations in temperature and activity. Therefore, we compared two groups of South American rattlesnakes, Crotalus durissus, with the vagus nerve intact or severed, subjected to the same conditions of temperature and activity. Hemodynamic parameters were measured by occlusive cannulation. Generally, increasing the temperature and the activity increased heart rate (fH), cardiac output (CO), pulmonary blood flow (Qpul) and systemic blood flow (Qsys), although only activity has caused to develop a R-L shunt in response to increased demand for O2 in the tissues. The activity was also responsible for increase in mean systemic and pulmonary arterial pressure. Unilateral vagotomy also increased blood flow, but did not affect fH. The absence of vagal control has more effect in controlling Rpul, causing changes in shunt patterns, especially when the animal was active. Under such condition, the organism seemed to offset the effects on hemodynamic shunt, resulting from changes in systemic resistance, with changes in CO. Thus, CO is elevated until Qpul is at an... (Complete abstract click electronic access below)
In non crocodilian reptiles, the ventricle is partially divided and allows venous blood, low in oxygen, to recirculate the systemic circuit, which is referred to as a right-to-left shunt (R-L shunt), or the oxygen-rich blood to return to the pulmonary circuit, referred to as a left-to-right shunt (L-R shunt). In theory, if intracardiac shunts provide any adaptive advantage, it would be controlled rather than be a passive consequence of changes in vascular resistances. The vagus nerve innervates the pulmonary trunk and has a role in controlling the resistance of the pulmonary circuit (Rpul). Thus, the control of Rpul could set the direction of the resulting shunt. In this study we hypothesized that the lack of vagal tone causes changes in control of intracardiac shunts in animals subjected to variations in temperature and activity. Therefore, we compared two groups of South American rattlesnakes, Crotalus durissus, with the vagus nerve intact or severed, subjected to the same conditions of temperature and activity. Hemodynamic parameters were measured by occlusive cannulation. Generally, increasing the temperature and the activity increased heart rate (fH), cardiac output (CO), pulmonary blood flow (Qpul) and systemic blood flow (Qsys), although only activity has caused to develop a R-L shunt in response to increased demand for O2 in the tissues. The activity was also responsible for increase in mean systemic and pulmonary arterial pressure. Unilateral vagotomy also increased blood flow, but did not affect fH. The absence of vagal control has more effect in controlling Rpul, causing changes in shunt patterns, especially when the animal was active. Under such condition, the organism seemed to offset the effects on hemodynamic shunt, resulting from changes in systemic resistance, with changes in CO. Thus, CO is elevated until Qpul is at an... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Animais - Fisiologia, Animal physiology, Hemodinâmica, Fluxo sanguineo, Reptil, Vagotomia, Sistema cardiovascular, Sangue - Circulação, Morfologia (Animais)
Como citar
FILOGONIO, Renato. Influência do controle vagal na resistência vascular pulmonar e desvio intracardíaco em Crotalus durissus (Squamata: Viperidae). 2012. 63 f. Dissertação - (mestrado) - Universidade Estadual Paulista, Instituto de Biociências de Rio Claro, 2012.