Studies on hyperthermic ceiling of cAMP and its relation to hyperthermic ceiling of pyrogen / 中国病理生理杂志

ABSTRACT

Some results obtained by others showed the limitation of cyclic 3', 5'-adenosine monophosphate (cAMP) increase within the brain might be an important factor in endogenous pyrogen (EP) hyperthermic ceiling (HC) or endotoxin (ET) HC. The results obtained from our experiments indicated (1) Lateral cerebro-ventricular administration of dibutyryl cAMP (Db-cAMP) induced dose-dependent fever in rabbits. But there was no further increase in body temperature when the fever reached a certain height, even if Db-cAMP doses were increased progressively, "a flat slope" appeared in the dose response curve. This is termed "cAMP HC" by the authors. (2) Level of fever cavsed by non-HC dose Db-cAMP with non-HC dose EP was markedly higher than that of non-HC dose EP or non-HC dose Db-cAMP, and was similar to the sum of action caused by non-HC dose Db-cAMP and non-HC dose EP. (3) Similar were the levels of HC caused by EP, Db-cAMP and Db-cAMP with the charge of HC dose EP. But the level of HC caused by ET or Db-cAMP HC with the charge of HC dose ET was higher than that of cAMP.The authors deduce that the cAMP may be an important central mediator in pyrogen-induced fever; the cAMP HC developed may be a result of saturation of cAMP action site within the brain or the limitation of production of other mediators induced by cAMP; the formation of EP HC or ET HC may be influenced not only by the limitation of cAMP increase, but also by the saturation of cAMP action site, within the brain; ET fever and ET HC differed greatly from those of EP; besides cAMP, other factors may be involved in the formation of ET HC.