Subramanian Madhan, Mueller Patrick J
Department of Physiology, Wayne State University School of Medicine Detroit, MI, USA.
Front Physiol. 2016 Jul 19;7:290. doi: 10.3389/fphys.2016.00290. eCollection 2016.
Despite the classically held belief of an "all-or-none" activation of the sympathetic nervous system, differential responses in sympathetic nerve activity (SNA) can occur acutely at varying magnitudes and in opposing directions. Sympathetic nerves also appear to contribute differentially to various disease states including hypertension and heart failure. Previously we have reported that sedentary conditions enhanced responses of splanchnic SNA (SSNA) but not lumbar SNA (LSNA) to activation of the rostral ventrolateral medulla (RVLM) in rats. Bulbospinal RVLM neurons from sedentary rats also exhibit increased dendritic branching in rostral regions of the RVLM. We hypothesized that regionally specific structural neuroplasticity would manifest as enhanced SSNA but not LSNA following activation of the rostral RVLM. To test this hypothesis, groups of physically active (10-12 weeks on running wheels) or sedentary, male Sprague-Dawley rats were instrumented to record mean arterial pressure, LSNA and SSNA under Inactin anesthesia and during microinjections of glutamate (30 nl, 10 mM) into multiple sites within the RVLM. Sedentary conditions enhanced SSNA but not LSNA responses and SSNA responses were enhanced at more central and rostral sites. Results suggest that enhanced SSNA responses in rostral RVLM coincide with enhanced dendritic branching in rostral RVLM observed previously. Identifying structural and functional neuroplasticity in specific populations of RVLM neurons may help identify new treatments for cardiovascular diseases, known to be more prevalent in sedentary individuals.
尽管传统观念认为交感神经系统的激活是“全或无”的，但交感神经活动（SNA）的差异反应可能会在不同程度和相反方向上急性发生。交感神经似乎也对包括高血压和心力衰竭在内的各种疾病状态有不同的影响。此前我们报道过，久坐不动会增强大鼠内脏交感神经活动（SSNA）对延髓头端腹外侧区（RVLM）激活的反应，但不会增强腰交感神经活动（LSNA）。久坐大鼠的延髓脊髓RVLM神经元在RVLM头端区域也表现出树突分支增加。我们假设，区域特异性结构神经可塑性将表现为头端RVLM激活后SSNA增强而LSNA不增强。为了验证这一假设，将体力活动组（在跑轮上活动10 - 12周）或久坐的雄性Sprague-Dawley大鼠进行仪器植入，以记录在氯胺酮麻醉下以及向RVLM内多个部位微量注射谷氨酸（30 nl，10 mM）期间的平均动脉压、LSNA和SSNA。久坐状态增强了SSNA反应但未增强LSNA反应，且在更靠中心和头端的部位SSNA反应增强。结果表明，头端RVLM中增强的SSNA反应与之前观察到的头端RVLM中增强的树突分支一致。识别RVLM神经元特定群体中的结构和功能神经可塑性可能有助于确定治疗心血管疾病的新方法，已知这些疾病在久坐的个体中更为普遍。
