Holstein Gay R, Friedrich Victor L, Martinelli Giorgio P
Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, New York, 10029; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York, 10029.
J Comp Neurol. 2014 Jun 15;522(9):2053-74. doi: 10.1002/cne.23517.
Changes in head position and posture are detected by the vestibular system and are normally followed by rapid modifications in blood pressure. These compensatory adjustments, which allow humans to stand up without fainting, are mediated by integration of vestibular system pathways with blood pressure control centers in the ventrolateral medulla. Orthostatic hypotension can reflect altered activity of this neural circuitry. Vestibular sensory input to the vestibulo-sympathetic pathway terminates on cells in the vestibular nuclear complex, which in turn project to brainstem sites involved in the regulation of cardiovascular activity, including the rostral and caudal ventrolateral medullary regions (RVLM and CVLM, respectively). In the present study, sinusoidal galvanic vestibular stimulation was used to activate this pathway, and activated neurons were identified through detection of c-Fos protein. The retrograde tracer Fluoro-Gold was injected into the RVLM or CVLM of these animals, and immunofluorescence studies of vestibular neurons were conducted to visualize c-Fos protein and Fluoro-Gold concomitantly. We observed activated projection neurons of the vestibulo-sympathetic reflex pathway in the caudal half of the spinal, medial, and parvocellular medial vestibular nuclei. Approximately two-thirds of the cells were ipsilateral to Fluoro-Gold injection sites in both the RVLM and CVLM, and the remainder were contralateral. As a group, cells projecting to the RVLM were located slightly rostral to those with terminals in the CVLM. Individual activated projection neurons were multipolar, globular, or fusiform in shape. This study provides the first direct demonstration of the central vestibular neurons that mediate the vestibulo-sympathetic reflex.
头部位置和姿势的变化由前庭系统检测到，通常随后会出现血压的快速变化。这些补偿性调节使人类能够站立而不昏厥，是通过前庭系统通路与延髓腹外侧血压控制中心的整合来介导的。直立性低血压可反映该神经回路的活动改变。前庭交感神经通路的前庭感觉输入终止于前庭核复合体中的细胞，这些细胞进而投射到参与心血管活动调节的脑干部位，包括延髓头端和尾端腹外侧区域（分别为RVLM和CVLM）。在本研究中，使用正弦电前庭刺激来激活该通路，并通过检测c-Fos蛋白来识别被激活的神经元。将逆行示踪剂荧光金注入这些动物的RVLM或CVLM，并对前庭神经元进行免疫荧光研究，以同时观察c-Fos蛋白和荧光金。我们在前庭脊髓核、内侧前庭核和小细胞内侧前庭核的尾侧半部观察到前庭交感反射通路的激活投射神经元。在RVLM和CVLM中，约三分之二的细胞与荧光金注射部位同侧，其余为对侧。总体而言，投射到RVLM的细胞位置比其终末在CVLM的细胞略靠前。单个激活的投射神经元呈多极、球形或梭形。本研究首次直接证明了介导前庭交感反射的中枢前庭神经元。
