A novel central pathway links arterial baroreceptors and pontine parasympathetic neurons in cerebrovascular control
A novel central pathway links arterial baroreceptors and pontine parasympathetic neurons in cerebrovascular control
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DOI：
10.1023/a:1025059710382
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发表时间：
2003-10-01
影响因子：
4
通讯作者：
Talman, WT
中科院分区：
文献类型：
--
作者：
Agassandian, K;Fazan, VPS;Talman, WT
1.我们验证了动脉压力感受性反射通过连接心血管孤束核和桥脑副交感节前神经元的通路调节脑血管张力的假设.所有研究均使用麻醉大鼠。采用激光血流仪测量脑血流量。我们评估了压力感受器神经、孤束核本身、脑桥节前副交感神经元或脑血管副交感神经节神经损伤的动物对动脉血压升高的脑血管反应。在阻断翼腭神经节副交感神经释放的一氧化氮合成后，在动物中进行了类似的评估。最后评价谷氨酸刺激桥脑节前副交感神经元对脑血流量的影响.我们发现，病变的任何一个网站在假定的途径或中断一氧化氮合成导致延长自动调节的平均动脉压增加到高达200毫米汞柱的水平。相反，刺激脑桥副交感神经节前神经元导致脑血管舒张。第二个系列的研究利用经典的解剖示踪方法，以确定在光镜和电镜水平是否在心血管孤束核，压力感受器传入的终止网站，投射到脑桥节前神经元的神经元。用顺行示踪剂从孤束核追踪纤维到脑桥，用逆行示踪剂从脑桥追踪纤维到孤束核。利用双标记技术，我们进一步研究了标记的孤束核投射和神经节前神经元之间的突触，这些神经元本身被逆行示踪剂标记到翼腭神经节中.这些解剖学研究表明，孤束核直接投射到脑桥节前神经元，并与这些神经元形成不对称的、看似兴奋性的突触。这些研究提供了强有力的证据表明，动脉压力感受器可能通过与脑桥副交感神经元的直接联系来调节脑血流量。需要进一步的研究来阐明这一途径在整合生理学中的作用。
1. We tested the hypothesis that arterial baroreceptor reflexes modulate cerebrovascular tone through a pathway that connects the cardiovascular nucleus tractus solitarii with parasympathetic preganglionic neurons in the pons.2. Anesthetized rats were used in all studies. Laser flowmetry was used to measure cerebral blood flow. We assessed cerebrovascular responses to increases in arterial blood pressure in animals with lesions of baroreceptor nerves, the nucleus tractus solitarii itself, the pontine preganglionic parasympathetic neurons, or the parasympathetic ganglionic nerves to the cerebral vessels. Similar assessments were made in animals after blockade of synthesis of nitric oxide, which is released by the parasympathetic nerves from the pterygopalatine ganglia. Finally the effects on cerebral blood flow of glutamate stimulation of pontine preganglionic parasympathetic neurons were evaluated.3. We found that lesions at any one of the sites in the putative pathway or interruption of nitric oxide synthesis led to prolongation of autoregulation as mean arterial pressure was increased to levels as high as 200 mmHg. Conversely, stimulation of pontine parasympathetic preganglionic neurons led to cerebral vasodilatation. The second series of studies utilized classic anatomical tracing methods to determine at the light and electron microscopic level whether neurons in the cardiovascular nucleus tractus solitarii, the site of termination of baroreceptor afferents, projected to the pontine preganglionic neurons. Fibers were traced with anterograde tracer from the nucleus tractus solitarii to the pons and with retrograde tracer from the pons to the nucleus tractus solitarii. Using double labeling techniques we further studied synapses made between labeled projections from the nucleus tractus solitarii and preganglionic neurons that were themselves labeled with retrograde tracer placed into the pterygopalatine ganglion.4. These anatomical studies showed that the nucleus tractus solitarii directly projects to pontine preganglionic neurons and makes asymmetric, seemingly excitatory, synapses with those neurons. These studies provide strong evidence that arterial baroreceptors may modulate cerebral blood flow through direct connections with pontine parasympathetic neurons. Further study is needed to clarify the role this pathway plays in integrative physiology.