Analysis of functional connection of the dorsomedial hypothalamic nucleus for themoregulation

下丘脑视前区（POA）在体温调节神经元回路中占有重要地位。最近，有报道称下丘脑背内侧（DMH）参与了热量产生的控制。因此，在本研究中，我们研究了与大鼠下丘脑背内侧（DMH）有功能传入连接的大脑区域，使用免疫组织化学分析，将一种逆行示踪剂霍乱毒素b（CTb）注射到DMH和Fos表达中，以响应温暖（33℃）或寒冷（10℃）暴露。双标记细胞被定义为神经元与DMH在体温调节方面具有功能连接。温暴露大鼠仅在视前正中区（MnPO）获得双标记细胞。低温暴露大鼠下丘脑前部（AH），尤其是其内侧和腹侧，获得了双标记细胞。Fos和CTb的研究结果提出了DMH神经元被MnPO神经元抑制的可能性，MnPO中的CTb- ir神经元具有gaba能，直接调节DMH神经元的活性。为了验证这种可能性，我们进一步研究了gaba能神经元标志物GAD67 mRNA在CTB-IR MnPO神经元中的表达。我们发现79.6%的CTb-IR细胞在MnPO中表现出gad67mrna的信号。这些结果表明，POA中的神经元，特别是MnPO中的神经元，接受来自皮肤的温暖输入并通过gaba能突触向DMH发送抑制信号以抑制热量产生，AH中的神经元接受来自皮肤的冷信号并向DMH发送兴奋信号以激活热量产生。

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.