Hypothalamic neuron responses in the vestibulo-autonomic reflex with special reference to the cerebellar nucleus and brainstem

下丘脑后核(PH)神经元对上、外侧VN刺激有兴奋性反应，对VN内侧、下VN刺激无反应。下丘脑室旁核(PVN)和PH区神经元对热刺激既有兴奋反应，也有抑制反应，冷热水刺激、对侧迷路和同侧迷路的兴奋/抑制反应模式相似。这些反应在切断前庭神经或迷路切除后几乎消失，表明上述反应起源于前庭。静脉注射H_2和H_2阻滞剂可使上述反应减弱、消失或逆转。这表明组胺能系统参与了前庭信息在脑内的传递。旋转开始后，PH神经元的自发放电逐渐改变，甚至在旋转结束后，这种变化也持续了几分钟。热刺激引起血压下降，这种变化与下丘脑室旁核神经元的活动变化有关。电毁损小脑顶核对血压变化影响不大，但电毁毁下丘脑几乎完全消除对热刺激反应的血压变化。这表明从前庭通过脑干网状结构到达下丘脑的通路在前庭-眼压上反射中起关键作用。迷走神经背核的神经元对同侧或对侧热刺激的反应主要是兴奋。

Posterior hypothalamic (PH)neurons responded excitatory in response to superior and lateral vesutibular nuclei(VN)stimulation and not to medial and inferior VN stimulation. The neurons in the PH and hypothalamic paraventricular nucleus(PVN) responded either excitatory or inhibitory to caloric stimulstion, and the individual neurons excitaion/inhibition response pattern was ssimilar when stimulated with either hot or cold water and on either the contralateral or ipsilateral labyrinth. These responses were almost disappeared after sectioning the vestibular nerve or labyrinthectomy, suggesting that the above responses were vestibular in origin. Furthermore, these responses were diminished, disappeared or reversed by intravenous H_2 and H_2 blocker infusion. This indicates that the histaminergic systemparticipates in the vestibular information transduction in the brain. The spontaneous discharge of PH neurons gradually changed after the rotation began and these changes lasted for several minutes even after the rotation ended. Caloric stimulation produced a decrease in blood pressure (BP)and this change was related to the activity change of PVN neurons. Although electric destruction of the fastigial nucleus in the cerebellum produced little effect on the BP change, electric destruction of the hypothalamus almost totally abolished the BP change in responses to the caloric stimulation. This means that the acsending pathway from the vestibularcleus to the hypothalamus via the brainstem reticular formation has a crucial role in the vestibulo-sutonomic reflex., The neurons in the dorsal nucleus of the vagus showed mainly excitation in response to either ipsilateral or contralateral caloric stimulation.