NEURONAL RESPONSES TO VESTIBULAR STIMULATION IN THE GUINEA-PIG HYPOTHALAMIC PARAVENTRICULAR NUCLEUS

We investigated the effects of caloric stimulation on neuronal activit y in the hypothalamic paraventricular nucleus (PVN) in anesthetized gu inea pigs. Hot water stimulation of the contralateral labyrinth produc ed excitation in 29.4% of the PVN neurons tested, while cold water pro duced excitation in 22.2% of the neurons. Hot water resulted in inhibi tion of 22.4% of the neurons and cold water inhibition of 24.7% of the neurons. Intracranial vestibular nerve section greatly reduced respon siveness of the PVN neurons to caloric stimulation, indicating that th e majority of the responses observed were vestibular in origin. The re sponse pattern of the individual PVN neurons was similar following hot and cold water stimulation and after stimulation of the contralateral and ipsilateral labyrinths. These results suggest that the PVN neuron s receive vestibular afferents bilaterally according to the intensity of vestibular stimulation, with the information received probably inte grated in the hypothalamus to participate in vestibule-autonomic refle xes.