内生致冷原作用机制的研究

家兔侧脑室内注射纯化内生致冷原(endogenous cryogen,EC)引起直肠温度下降和耳皮肤温度上升,其反应与静脉注射的情况相似,但直肠温度降低更加迅速,所用剂量仅为静脉注射达到同样效应时的1/80。静脉注射EC降温反应过程中,体温下降至最低点时脑脊液cAMP浓度显著下降,而cGMP浓度没有显著改变,血浆cAMP和cGMP浓度均显著升高;体温回升至正常水平时脑脊液、血浆cAMP和cGMP浓度均与对照组无显著差异。本实验结果提示:(1)EC的主要作用部位可能是中枢神经系统;(2)cAMP可能参与EC降温反应的中枢机制。

Studies on hypothermic mechanisms of endogenous cryogen(EC)

Intracerebroventricular administration of purified EC induced a fall in rectal temperature of rabbits with an increase in ear skin temperature. Only 1/80th the amout of purified EC injected i. v. produced a comparable fall in rectal temperature when injected into the lateral ventricle of rabbits. ICV administration of purified EC resulted in a more rapid fall in rectal temperature than i. v. administration. This evidence strongly supports the hypothesis that EC has a primary site of action in the central nervous system.After intravenous administration of purified EC, with a fall in rectal temperature there was a significant decrease in levels of cyclic AMP in the cerebrospinal fluid of rabbits, but no change was found in levels of cyclic GMP in the cerebrospinal fluid. These data suggest that EC might induce hypothermia in rabbits by lowering levels of cyclic AMP in the brain and that cyclic GMP might not be involved in hypothermia caused by EC.