REGULATION OF CBF BY THE ROSTRAL VENTROLATERAL MEDULLA

延髓头端腹外侧区神经元的描述性兴奋 提高大脑皮层内局部脑血流量(RCBF) 而不会提升大脑新陈代谢。这些神经元也介导了一半的 低氧状态下脑血管扩张。三项研究将是 在麻醉大鼠中进行rCBF(激光多普勒血流仪) 脑电波将被测量。研究1测试以下假设：(A)神经元在 介导脑血管扩张的RVL在地形图上 与网状脊髓交感兴奋神经元不同， 前者定位于尾侧(RVLc)，后者定位于吻侧(RVLr)亚区。 (B)氧检测神经元定位于RVLr但兴奋， 通过髓内通路，RVLc中的神经元升高rCBF；和(C) RVLc神经元也参与大脑皮层活动的同步化 电刺激和化学刺激引起的脑干核团 单人组(NTS)。研究II结合使用解剖示踪技术 有损害和电生理记录的诱发活动：(A) 建立RVLc可能介导的传出投射靶点 脑血管扩张，主要集中在大脑中的神经元 中线-板层内丘脑、未确定带和下丘脑背侧；和(B) 通过逆行标记，确定投射到皮质和 被RVL支配，当刺激时，会升高rCBF，当 阻断，将阻断RVLc引起的血管扩张。研究III测试 假设一个特定的皮质神经元亚群，可能 对氧敏感的，总是由神经源性传入兴奋 血管扩张部位，包括RVL，并因此转导传入 神经活动转化为血管扩张。神经元将通过以下方式进行识别 细胞外和细胞内染色，并将表型特征 通过光学显微镜观察其形态及其与大脑的关系 微循环。

DESCRIPTION Excitation of neurons of the rostral ventrolateral medulla (RVL) elevates regional cerebral blood flow (rCBF) within the cerebral cortex without elevating cerebral metabolism. These neurons also mediate half of the cerebrovascular vasodilatation to hypoxia. Three studies will be undertaken in anesthetized rats in which rCBF (by laser-Doppler flowmetry) and EEG will be measured. Study 1 tests the hypotheses that (a) neurons in RVL which mediate the cerebrovascular vasodilation are topographically distinct from the reticulo-spinal sympathoexcitatory neurons, with the former localized to caudal (RVLc) and the latter to rostral (RVLr) subareas, respectively; (b) oxygen detecting neurons are localized to RVLr but excite, over an intramedullary pathway, neurons in RVLc to elevate rCBF; and (C) neurons of RVLc also mediate the synchronization of electrocortical activity elicited by electrical and chemical stimulation of the nucleus tractus solitarii (NTS). Study II uses anatomical tracer techniques in conjunction with lesions and electrophysiological recording of evoked activity to: (a) establish the targets of efferent projections from RVLc which might mediate the cerebrovascular vasodilation, focusing on neurons of midline-intralaminar thalamus, zona incerta and dorsal hypothalamus; and (b) determine, by retrogradely labeling, sites projecting to the cortex and innervated by RVL, which, when stimulated, will elevate rCBF and, when interrupted, will block the vasodilation elicited by RVLc. Study III tests the hypothesis that a specific subpopulation of cortical neurons, possible oxygen-sensitive, are invariably excited by neurogenic afferentation for vasodilatory sites, including RVL, and as a result transduce afferent neuronal activity into vasodilation. The neurons will be identified by extra- and intracellular staining and will be phenotypically characterized by light microscopy with respect to morphology and in relation to cerebral microcirculation.