| Co-Investigator(Kenkyū-buntansha) |
NAGASHIMA Kei Faculty of Medicine, Osaka University, Assistant, 医学部, 助手 (40275194)
INOUE Osamu Faculty of Medicine, Osaka University, Professor, 医学部, 教授 (50159969)
YAMATODANI Atsushi Faculty of Medicine, Osaka University, Professor, 医学部, 教授 (30116123)
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| Research Abstract |
Thermosensitive neurons in the hypothalamus, especially in the preoptic area (PO), play important roles in thermoregulation (Boulant, 1980; Simon et al., 1986), but many hypotheses about signal processing in the hypothalamus have remained untested because we don't have precise enough information about the neuronal "network" there. Although it had long been almost an article of faith that warm-sensitive neurons send efferent signals driving heat loss and cold-sensitive neurons send efferent signals driving heat production, we found that warm-sensitive neurons work for the control of heat production as well as heat loss (Zhang et al., 1995). But we have obtained evidence that the PO is simply an assembly of neuronal groups, each sending its own efferent signals to each effector, and that these groups function without connections to each other (Kanosue et al., 1997). In the present study, based upon these findings, we further analyzed the neural network for thermoregulation in the hypothalamus and the midbrain. First, we analyzed the nertwork for nonshivering thermogenesis. Electrical stimulation of the ventromedial hypothalamus elicited thermogenesis of the brown adipose tissure. But the same stimulus had no effect during warming the preoptic area, which means that the PO send inhibitory signals to the VMH. Second, the role of the posterior hypothalmus was investigated by injecting inhibitory substance muscimol. Muscimol injection suppressed cold-induced shivering, which indicates that the excitatory neuron for shivering locates in the posterior hypothalamus. Third, DLH was injected into the ventropoterior region of the PAG and it facilitated nonshivering thermogenesis. The retrograde tracer CTB injection into the medullary raphe labeled neurons in the PAG where nonshivering thermogenesis was facilitated. The excitatory signal seems to decsend from the PAG to the raphe.
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