Brain blood flow regulation of the brainstem

In anesthetized, paralyzed and artificially ventilated rats, the nucleus tractus solitarii (NTS), caudal ventrolateral medullary depressor area (VLDA), and rostral ventrolateral medullary pressor area (VLPA) were chemically stimulated. The roles of these areas on cerebral and spinal cord circulation, the receptor type of the NTS to control cerebral circulation, and the interaction between the VLDA and the VLPA were investigated. The NTS, VLDA, and VLPA have vasoconstrictor effects on the cerebral circulation, respectively. The VLPA has a vasoconstrictor effect on spinal cord circulation. The greater petrosal nerve (GPN) cell group, which is a subgroup of the superior salivatory nucleus, may constitute a parasympathetic cerebrovasodilator center. The NMDA receptors in the NTS may be involved in the control of cerebral circulation. The vasoconstrictive pathway to control cerebral vessels from the VLDA is mediated via the VLPA and the cervical sympathetic nerves. The present results also suggest that there may be a sympathoexcitatory pathway from the VLDA to the VLPA for controlling cerebral vessels and a sympathoinhibitory pathway from the VLDA to the VLPA for controlling systemic vessels. These different roles of the pathways from the VLDA to the VLPA for the different organs may explain the regional differences of the sympathetic nerves activities.