Examination of the hyposesis of thermoredulatory module in the hypothalamus.

下丘脑的热敏神经元，特别是视前区（PO）的热敏神经元，在体温调节中发挥着重要作用（Boulant, 1980; Simon et al., 1986），但由于我们对那里的神经元“网络”没有足够精确的信息，许多关于下丘脑信号处理的假设仍未得到检验。虽然热敏感神经元发出驱动热损失的传出信号和冷敏感神经元发出驱动热产生的传出信号长期以来几乎被认为是一种信念，但我们发现，热敏感神经元既控制热产生，也控制热损失（Zhang et al., 1995）。但我们已经获得的证据表明，PO只是神经元群的一个集合，每个神经元群向每个效应器发送自己的输出信号，并且这些神经元群的功能彼此之间没有联系（Kanosue et al., 1997）。在本研究中，基于这些发现，我们进一步分析了下丘脑和中脑的体温调节神经网络。首先，我们分析了非瑟瑟生热的网络。电刺激下丘脑腹内侧引起棕色脂肪组织的产热作用。但同样的刺激在加热视前区时没有效果，这意味着PO向VMH发送抑制信号。其次，通过注射抑制物质muscimol来研究下丘脑后部的作用。Muscimol注射抑制冷致寒战，说明寒战兴奋神经元位于下丘脑后部。第三，将DLH注射到PAG的腹后区，它促进了非颤抖产热。逆行示踪剂CTB注射到PAG中缝标记的髓质神经元中，促进了非寒颤产热。兴奋信号似乎从PAG下降到raphe。

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.