Does α-MSH of Pars Intermedia of Pituitary and Hypothalamus modulate Fos expression in brain of rats induced by IL-1β?

采用脑室注射剂量为1pg ~ 1ng/kg的重组人白细胞介素-1β(IL-1β)诱导大鼠痛觉过敏，α-MSH可抑制IL-1β的作用。据报道，ICV注射超过100ng的IL-1β可诱导大鼠下丘脑室旁核（PVN）中Fos的表达，但低剂量的ICV不会引起痛觉过敏。因此，了解中枢神经系统（CNS）中对IL-1β的感觉反应是很重要的。为了确定IL-1β在中枢神经系统中的激活部位，我们检测了大鼠下丘脑Fos蛋白的表达和α-MSH对IL-1β的调节作用。ICV注射10 pg IL-1β后，引起痛觉过敏，并在含有α-MSH神经元的PVN和弓形核（ARC）中表达Fos。而IL-1β对α-MSH外周分泌器官垂体中部（PI）的Fos表达无诱导作用。ICV预注射30 ng α-MSH可抑制痛觉过敏及PVN和ARC中Fos的表达。结果表明，IL-1β可激活PVN神经元，α-MSH可抑制IL-1β在PVN中的作用。因此，可能是ARC中含有内源性α-MSH的α-MSH神经元被激活抑制IL-1β的作用，而PI中的α-MSH细胞没有发生这种反应。

Hyperalgesia was induced by intracerebroventricular(ICV) administration of a recombinant human Interleukin-1β(IL-1β) of 1pg - 1ng/kg in rats and the effect of IL-1β was inhibited by amelanocyto stimulating hormone (α-MSH). It has been described that an ICV injection over 100ng IL-1β induced Fos expression in the paraventricular nucleus (PVN) of the hypothalamus in rats, but not in lower doses inducing hyperalgesia. Therefore It is important to know where the sensory response to IL-1β is mediated in the central nerves system (CNS). In order to establish the activated part in the CNS by IL-1β, we examined Fos protein expression in the hypothalamus and modulation by α-MSH for the response to IL-1β in rats. Following the ICV injection of 10 pg IL-1β, a hyperalgesia was induced and Fos was expressed in the PVN and the arcuate nucleus (ARC) which contained α-MSH neurons. But IL-1β did not induce Fos expression in pars intermedia (PI) of pituitary gland which is α-MSH secrete organ in the periphery. A ICV pre-injection of 30 ng α-MSH inhibited hyperalgesia and Fos expression in the PVN and the ARC. This observation demonstrated that PVN neurons were activated by IL-1β and α-MSH inhibited these effects of IL-1β in the PVN. Therefore it is possible that α-MSH neurons in the ARC, which contains endogenous α-MSH were activated to inhibit the effects of IL-1β but α-MSH cells in the PI were not committed with this reaction.