充胀犬胸部降主动脉所致的升压效应

在17只麻醉开胸犬,观察局部充胀胸部降主动脉(TDA)对心血管活动的影响。主要结果如下:1.充胀 TDA 引起心率、心肌收缩力、肾及股薄肌灌注压和全身动脉血压增加;TDA 局部去神经后反应消失,表明上述心血管效应系 TDA 受牵张刺激引起的正反馈性神经反射现象。2.切断动物两侧颈迷走神经和窦神经后,充胀 TDA 引起的心血管效应增大。3.用心得安(1mg/kg)消除心脏的β-效应后,充胀 TDA 引起的升压反应有所减小;用酚妥拉明(3mg/kg)阻断血管的α-受体效应后,多数动物即不再出现血压增高,从而提示充胀TDA 时的血压升高主要是反射性外周阻力增加所致。在缓冲神经完整的条件下,上述 TDA加压效应是存在的,但主动脉弓和颈动脉窦缓冲反射对其有对抗作用。

A PRESSOR EFFECT INDUCED BY DISTENDING THORACIC DESCENDIND AORTA IN DOGS

Cardiovascular effects induced by distending the thoracic descending aorta(TDA)were observed in 17 open-chest anesthetized dogs.The results obtained wereas follows:(1)TDA distention resulted in increase of heart rate,myocardial con-tractile force,renal and gracilis perfusion pressure,and systemic arterial pressure.These responses were abolished by local denervation of TDA.(2)Following bila-teral vagotomy and denervation of the carotid sinuses,the cardiovascular effects eli-cited by TDA distention were successively augmented.(3)The pressor responsecould be reduced to some extent by propranolol(lmg/kg,iv)and almost eliminatedby phentolamine(3 mg/kg,iv).On the basis of the above-mentioned results,itwas suggested that the cardiovascular effects induced by TDA distention were a po-sitive feedback adjustment,and such a pressor response resulted mainly from reflexincrease of peripheral resistance.The depressor reflex from aortic arch and carotidsinus could suppress the pressor reflex from the stretch receptor of TDA.