In order to study the mechanisms of ET and EP hyperthermic ceiling the concentration of cAMP in samples of c. s. f. and plasma were measured using the competitive protein binding assay after intraveneous injections of ET and EP in doses of nonhyperthermic ceiling, hyperthermic ceiling and hyperthermic ceiling plus the other pyrogen load. The results showed: (1) The concentration of cAMP in c. s. f. was elevated markdly with increase of fever reaction induced by EP, and was limited when EP hyperthermic ceiling was reached. But there was no analogous change of cAMP in plasma. (2) The contents of cAMP both in c. s. f. and in plasma were apparently correlated simultaneously to fever reaction induced by ET, and were limited when ET hyperthermic ceiling was reached. (3) Although the febrele level of ET hyperthermic ceiling was evidently hegher than that of EP and the altitude of fever exceed EP hyyerthermic ceiling when EP hyperthermic ceiling was added the load of ET. Contents of cAMP in c. s. f. had no significant differences among these groups. The results above indicate that the inhibition of central cAMP synthesis is closely related to the formation of EP hyperthermic ceiling and also is one of an important factors that induce. ET hyperthermic ceiling, which, however, is involved in other mediator except cAMP.

In order to study mechanisms of endotoxin (ET) and endogenous pyrogen (EP) byperthermic ceilings, the febrile responses induced in rabbits by intravenous injection of varying doses of EP were observed, and the doses in which the febrile reactions of rabbits to ET and EP are limited by hyperthermic ceiling were identified. Furthermore, the febrile reactions of typerttermic ceiling plus different pyrogen load were observed. T, e experiment stowed: 1. The level of ET hypert ermic ceiling is notably higher in comparison to that of EP hypertiermic ceiling. The findings indicated that the mechanisms of ET fever and ET Lyperthermic ceiling are different from those of EP fever and EP hyperthermic ceiling. 2. After EP hyperthermic ceiling was added the load of ET. the altitude of fever exceeded the EP hyperthermic ceiling; but after ET hypertthermic ceiling was added the load of EP, the altitude couldn't exceed ET hyperthermic ceiling. The results suggested that ET hyperthermic ceiling contained EP hyperttermic ceiling. The latter was an important component of ET hyperttermic ceiling, but there are other factors participating in the mechanisms of ET fever and ET hyperthermic ceiling except EP.