| Budget Amount *help |
¥15,200,000 (Direct Cost: ¥15,200,000)
Fiscal Year 2004: ¥5,900,000 (Direct Cost: ¥5,900,000)
Fiscal Year 2003: ¥9,300,000 (Direct Cost: ¥9,300,000)
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| Research Abstract |
The preoptic area(POA) in the hypothalamus occupies a crucial position in the neuronal circuit for thermoregulation. Recently, the dorsomedial hypothalamus(DMH) was reported to be involved in the control of heat production. Therefore, in the present study, we investigated the brain areas that had functional afferent connections with the dorsomedial hypothalamus(DMH) for thermoregulation in rats, using immuno-histochemical analyses of a retrograde tracer, cholera toxin-b(CTb), injected into the DMH and Fos expression in response to warm (33℃) or cold (10℃) exposure. A double-labeled cell was defined as the neuron had functional connection with the DMH in relation to thermoregulation. In the warm-exposed rats, double-labeled cells were obtained only in the median preoptic area(MnPO). In the cold exposed rats, double-labeled cells were obtained in the anterior hypothalamus(AH), especially in its medial and ventral parts. The results in the Fos and CTb studies raised a possibility that the DMH neurons would be inhibited by the MnPO neurons, and CTb-IR neurons in the MnPO would be GABAergic and directly regulate activity of the DMH neurons. To examine this possibility, we further investigated an expression of mRNA for GAD67,a marker for GABAergic neuron, in CTB-IR MnPO neuron. We found that 79.6% of CTb-IR cells in the MnPO exhibited signals for GAD67 mRNA. These results suggest that the neurons in the POA, especially in the MnPO, receive warm inputs from the skin and send inhibitory signals, via GABAergic synapses, to the DMH to suppress heat production, and the neurons in the AH receive cold signals from the skin and send excitatory signals to the DMH, to activate heat production.
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