Li J, Mitchell J H
Department of Internal Medicine, Harry S. Moss Heart Center, The University of Texas Southwestern Medical Center, Dallas, Texas 75235-9174, USA.
Am J Physiol Heart Circ Physiol. 2000 Dec;279(6):H2986-93. doi: 10.1152/ajpheart.2000.279.6.H2986.
The periaqueductal gray (PAG) of the midbrain is involved in the autonomic regulation of the cardiovascular system. The purpose of this study was to determine if static contraction of the skeletal muscle, which increases arterial blood pressure and heart rate, activates neuronal cells in the PAG by examining Fos-like immunoreactivity (FLI). Muscle contraction was induced by electrical stimulation of the L7 and S1 ventral roots of the spinal cord in anesthetized cats. An intravenous infusion of phenylephrine (PE) was used to selectively activate arterial baroreceptors. Extensive FLI was observed within the ventromedial region (VM) of the rostral PAG, the dorsolateral (DL), lateral (L), and ventrolateral (VL) regions of the middle and caudal PAG in barointact animals with muscle contractions, and in barointact animals with PE infusion. However, muscle contraction caused a lesser number of FLI in the VM region of the rostral PAG, the DL, L, and VL regions of the middle PAG and the L and VL regions of the caudal PAG after barodenervation compared with barointact animals. Additionally, the number of FLI in the DL and L regions of the middle PAG was greater in barodenervated animals with muscle contraction than in barodenervated control animals. Thus these results indicated that both muscle receptor and baroreceptor afferent inputs activate neuronal cells in regions of the PAG during muscle contraction. Furthermore, afferents from skeletal muscle activate neurons in specific regions of the PAG independent of arterial baroreceptor input. Therefore, neuronal cells in the PAG may play a role in determining the cardiovascular responses during the exercise pressor reflex.
中脑导水管周围灰质（PAG）参与心血管系统的自主调节。本研究的目的是通过检测Fos样免疫反应性（FLI）来确定增加动脉血压和心率的骨骼肌静态收缩是否会激活PAG中的神经元细胞。在麻醉的猫中，通过电刺激脊髓的L7和S1腹根来诱导肌肉收缩。静脉注射去氧肾上腺素（PE）用于选择性激活动脉压力感受器。在有肌肉收缩的压力感受性完好的动物以及有PE输注的压力感受性完好的动物中，在延髓头端PAG的腹内侧区域（VM）、中脑和尾端PAG的背外侧（DL）、外侧（L）和腹外侧（VL）区域观察到广泛的FLI。然而，与压力感受性完好的动物相比，去压力神经支配后，肌肉收缩在延髓头端PAG的VM区域、中脑PAG的DL、L和VL区域以及尾端PAG的L和VL区域引起的FLI数量较少。此外，有肌肉收缩的去压力神经支配动物中脑PAG的DL和L区域的FLI数量比去压力神经支配的对照动物更多。因此，这些结果表明，在肌肉收缩过程中，肌肉感受器和压力感受器的传入输入均激活PAG区域中的神经元细胞。此外，来自骨骼肌的传入神经独立于动脉压力感受器输入激活PAG特定区域中的神经元。因此，PAG中的神经元细胞可能在运动升压反射期间确定心血管反应中发挥作用。
