Analysis of neuronal network for temperature regulation.

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The body temperature of homeothermic animal is controlled by multiple autonomic and behabioral responses and themoreceptors are distributed throughout the body. This multiple input-output system is regulated by the central nervous system, on the top of which the hypothalamus uncluding the preoptic area is located. The neuronal network for thermoregulation has been investigated by stimulation and ablation of the brain, and the importance of the hypothalamus became apparent. In spite of the flourishing outcome of single unit studies, there is almost no advance in our knowledge of the thermoregulatory "network", which makes it difficult to link electrophysiological and pharmachological data directly with thermoregulatory responses observed in whole animals. We don't know yet, for example, what groups of neuron are working for control of each effector response, and where they send efferent signals. This project was planned to connect this "missing link" in the study of thermoregulation. Fi … More rst, we analyzed efferent projection from the proptic area for thermoregulatory vasomotion. Electrophisilogical and ablation study revealed that warm sensitive neurones of the preoptic area send (1) inhibitory signals to the ventral tegmental area and (2) excitatory signals to the PAG for thermoregulatory vasomotor bontrol. Next the results of electrical stimulations had long ago showed that the posterior hypothalamus (PH) is important for the control of shivering, but it was not clear whether it was neurons that ware stimulated or it is only passing fibers. We found that cold-induced shivering was suppressed aftor muscimol, an agonist of the GABAa receptor, was injected into the PH,which therefore must contain neurons that send excitatory signals that elicit shivering. But PO warm-sensitive neurons may send inhibitory signals directly to a lower neuronal structure, bypassing the PH,since PO warming has been found to suppress shivering in animals whose PH was isolated from other hypothalamus. Less