Machado B H, Brody M J
Department of Pharmacology, University of Iowa, College of Medicine, Iowa City 52242.
Am J Physiol. 1990 Nov;259(5 Pt 2):R955-62. doi: 10.1152/ajpregu.1990.259.5.R955.
We showed previously that activation of nucleus ambiguus (NA) induced bradycardia and increased arterial pressure. In this study, we compared responses produced by electrical and chemical (glutamate) stimulation of NA and adjacent rostral ventrolateral medulla (RVLM). Equivalent pressor responses were elicited from both areas. However: 1) The response from RVLM was elicited at a lower frequency. 2) Regional vascular resistance changes were different, i.e., electrical stimulation of NA increased vascular resistance in hindquarters much more than the renal and mesenteric beds. In contrast, electrical and chemical stimulation of RVLM produced a more prominent effect on the renal vascular bed. 3) Bradycardia was elicited from NA at lower current intensity. 4) Glutamate produced bradycardia only when injected into NA. Studies in rats with sinoaortic deafferentation showed that bradycardic response to activation of NA was only partly reflex in origin. We conclude that 1) NA and RVLM control sympathetic outflow to regional vascular beds differentially and 2) the NA region involves parasympathetic control of heart rate and sympathetic control of arterial pressure.
我们之前表明，疑核（NA）的激活会诱发心动过缓和动脉压升高。在本研究中，我们比较了对NA和相邻的延髓头端腹外侧区（RVLM）进行电刺激和化学（谷氨酸）刺激所产生的反应。两个区域均可引发等效的升压反应。然而：1）RVLM的反应在较低频率下即可引发。2）局部血管阻力变化不同，即对NA的电刺激使后肢血管阻力增加的幅度远大于肾和肠系膜血管床。相反，对RVLM的电刺激和化学刺激对肾血管床产生的影响更为显著。3）以较低电流强度刺激NA即可引发心动过缓。4）谷氨酸仅在注入NA时才会引发心动过缓。对去窦弓神经大鼠的研究表明，对NA激活所产生的心动过缓反应仅部分源于反射。我们得出结论：1）NA和RVLM对局部血管床交感神经输出的控制存在差异；2）NA区域涉及对心率的副交感神经控制和对动脉压的交感神经控制。
