Effect of activation and blockade of central P2X receptors on body temperature

The aim of the present study was to elucidate the role of extracellular ATP acting on specific P2X receptors in the central mechanisms of thermoregulation. Using immunohistochemistry methods, it was found that the brainstem structures involved in the body temperature regulation contain a large number of nerve cells which possess P2X receptors for ATP. Experiments with intracerebroventricular application of a stable ATP analogue and P2X receptor antagonists to conscious rats showed that both activation and blockade of central P2X receptors resulted in marked changes in body temperature. Analysis of the effects of these agents suggests that ATP by acting on P2X receptors performs an important function in the mechanisms of transmission of afferent information coming from peripheral thermoreceptors to the brainstem thermoregulatory centres responsible for heat loss, and during pyrogen-induced fever can be involved in the action of the endogenous antipyretic system.     

Changes in the afferent activity of the vagus nerve and the rectal temperature in rats following Escherichia coli endotoxin administration]

In anaesthetised rats, i.p. administration of the Echerichia coli lipopolysaccharide in doses 5 mcg/kg (LPS) increased afferent activity of the cervical vagus, whereas 100 and 1000 mcg/kg doses inhibited the afferent discharges. Pyrogen-free saline (PFS) did not alter the activity. Rectal temperature (RT) was decreased by the PFS and by large doses of the LPS. Sodium salicylate administration prevented the effects.     

Antipyrogenic properties of oxytocin

Effects of oxytocin on pyrogenal or endogenous pyrogen-induced fever were studied. Intramuscular injection of oxytocin (0.2 micrograms/kg every half an hour) did not significantly affect the pattern of pyrogenal-induced fever. Constant intravenous injection of oxytocin (0.4 and 4 micrograms/kg/h) 2-4.5 h after pyrogenal decreased the rectal temperature, on an average, by 24% and 31%, respectively. Endogenous pyrogen fever was not attenuated by intravenous oxytocin (4 micrograms/kg/h). The antipyrogenic effect of oxytocin is related to inhibition of endogenous pyrogen synthesis rather than to blockade of its action, which is indicated by a decreased second peak of the temperature curve, inhibition of endogenous pyrogen synthesis in vitro, and persistence of the hyperthermic effect of endogenous pyrogen.     

Activity of blood interleukin-1 in dogs during work hyperthermia

The activity of interleukin-1 (IL-1) in blood plasma of the dogs in conditions of working hyperthermia was studied. The animals performed static exercise of submaximal capacity. Data on IL-1 circulation at different time after the onset of physical exercise were obtained. Cessation of exercise is accompanied by degradation of an IL-1 molecule to shorter fragments. The existence of the reserve pool of this biologically active substance released during intense muscle activity is suggested.