Studies on the involvement of intrahypothalamic angiotensin type 2 receptors in the development of fever in rats

我们最近发现，下丘脑(视前区和下丘脑前区)的血管紧张素II(Ang II)2型受体在下丘脑注射前列腺素E_2引起的发热中起重要作用。然而，血管紧张素转换酶II和2型受体是如何促进发烧的，目前还不清楚。我们推测，在发热期间，2型受体在大鼠的下丘脑中被诱导，导致发热增强。为了验证这种可能性，我们决定用免疫组织化学技术研究热原致热大鼠脑内2型受体的诱导。首先，我们制备了自己的抗2型受体抗体，用于免疫组织化学。实际上，我们合成了该受体的一个由11个氨基酸组成的C末端多肽，并将该多肽注射给兔三次。第一次注射8周后，获得抗血清，用亲和层析法纯化。我们使用这种抗体来检测无热和发热大鼠大脑中受体的诱导。但在腹腔注射的大鼠下丘脑内未检测到血管紧张素Ⅱ受体的信号。注射内毒素(1 mg/kg)或生理盐水。此外，侧脑室注射脂多糖(2μg)的大鼠在下丘脑没有显示任何受体信号。这些结果不支持在发烧期间在下丘脑诱导2型受体的假设。然而，我们将继续使用更复杂的高灵敏度技术来检验上述可能性(假设)。

We have recently found that angiotensin II (ANG II) type 2 receptors within the hypothalamus (preoptic and anterior hypothalamic region) play an important role in the fever induced by intrahypothalamic injection of prostaglandin E2. However, it is still unknown how ANG II and type 2 receptors contribute to the development of the fever. We speculated that during fever type 2 receptors are induced in the hypothalamus of the rats, leading to fever enhancement. In order to test this possibility, we decided to investigate the induction of the type 2 receptors in the brain of rats made febrile by the injection of pyrogens, using immunohistochemistry technique. At first, we made our own antibody against type 2 receptors for the immunohistochemistry. Actually, we synthesized a C-terminal peptide of the receptor consisting of eleven amino acids and injected this peptide three times to rabbits. Eight weeks after the first injection, the anti-serum was obtained and purified by affinity chromatography. We used this antibody to examine the induction of the receptors in the brain of afebrile and febrile rats. However, the signal of the ANG type 2 receptor was not detected in the hypothalamus of rats which received intraperitoneal (i.p.) injection of either LPS (1mg/kg) or saline. Furthermore, rats given intracerebroventricular injection of LPS (2μg) did not show any receptor signals in the hypothalamus. These results do not support the hypothesis that type 2 receptors are induced in the hypothalamus during fever. However, we will continue to examine the possibility (hypothesis) described above using more sophisticated techniques with high sensitivity.