大鼠内毒素性发热时不同脑区cAMP含量和腺苷酸环化酶活性的变化

给大鼠腹腔注射大肠杆菌内毒素(endotoxin, ET)复制发热模型,观察大鼠ET性发热时不同脑区组织cAMP含量和腺苷酸环化酶(adenylate cyclase, AC)活性的变化。结果发现:大鼠在发热高峰时与对照组比较,丘脑下部cAMP含量明显增加(P<0.01),并与体温变化呈正相关关系(r=0.827);丘脑下部AC活性也显著增强(P<0.001),也与体温变化呈正相关关系(r=0.774)。脑干AC活性显著增强(P<0.05),但与体温变化无正相关关系(r=0.203),cAMP含量也无明显变化。脑皮质cAMP含量和AC活性均无明显变化。以上结果显示:ET可能是通过共同信息物质——内生致热原(EP),以一定方式作用于丘脑下部视前区神经元的细胞膜内AC,使其活化作用于ATP,使ATP分解生成cAMP,从而使局部cAMP含量增加,再通过某种方式使体温调定点上移,导致体温升高。

Changes of cyclic AMP and adenylate cyclase in different areas of rat brain during fever induced by endotoxin

The fever was induced by intraperitoneal injecting of refined E.Coli endotoxin(ET). The cAMP level and the activity of adenylate cyclase (AC) in differen brain areas of rat were assayed.Both cAMP and AC in hypothalamus were increased significantly at the peak of fever in comparing with the control group (P<0.01 and P<0.001, respectively).The cAMP and AC activities were positively corelated with the change of body temperature. However, either the cAMP or the AC in cortex did not show any obvious changes Although the activity of AC in brainstem increased significantly (P<0.05),it was not positively corelated with the change of body temperature.According to the above results,the author infered that the endotoxin-induced fever might be mediated by endogenous pyrogen,a common substance of message,which activated (via certain mode) the AC on the neuron membrane in the preoptic anterious hypothalamus (PO/AH)where the AC catalyzed the conversion of ATP to produce more cAMP.The high concentration of cAMP in the PO/AH made the "set-point" of body temperature rise up and resulted in fever.