Role of Brainstem Autonomic Nuclei in Cerebrovascular Responses and Autonomic Nervous Functions

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Brainstem is the most important place in the central nervous system regulating vital signs. Anatomical pathways and neurotransmitters of the brainstem autonomic nuclei have been recently clarified, and locus ceruleus, a noradrenergic center, has close relationships with tractus solitary nucleus, Raphe nucleus and other nuclei. Most of their functional significances, however, remain to be elucidated. The aim of the present study was to investigate the roles of these brainstem nuclei in cerebral vasomotor responses and autonomic nervous functions.Monkeys (macaca fuscata) were lightly anesthetized with ketamine and immediately intubated. A catheter was inserted into a brachial artery for measuring blood pressure (BP) and pulse rate (PR). Hemodynamic functional tests (Valsalva's maneuver, Aschner's eyeball pressure test, cold pressur test and postural change) were performed. Subsequently, they were stereotaxically operated for producing an unilateral lesion by an electrical coagulation met … More hod and each sham lesion in locus ceruleus, tractus solitary nucleus or Raphe nucleus. One week later, following the repeated autonomic functional tests animals were anesthetized and artificially ventilated. PACO_2, and body temperature were kept within normal range. Bilateral internal carotid blood flow and vertebral blood flow were continuously measured by using electromagnetic flow meters simultaneously with BP, PR and respiration. Chemical vasomotor response and autoregulation of cerebral blood flow (CBF) were quantitatively analyzed. Changes in BP were induced by hemorrhage and infusion of the blood, changes in PACO_2, by 7% CO_2 + air inhalation and hyperventilation. The location of the lesion was verified after the study.The autonomic nervous functions, mainly those of the sympathetic nervous system, were impaired after the lesion of locus ceruleus. Chemical vasomotor responses of CBF were affected more significantly than CBF autoregulation. The impairment of chemical vasomotor responses by the lesion was more marked in the vertebrobasilar system compared to the carotid Less