Cyclo‐oxygenase mediation of endotoxin‐induced fever, anterior and posterior pituitary hormone release, and hypothalamic c‐Fos expression in the prepubertal pig

Abstract

Prepubertal pigs (n = 8) treated with bacterial endotoxin (20 micrograms lipopolysaccharide; LPS) exhibited a sustained (4 h) hyperthermia, increased plasma concentrations of cortisol, prolactin, growth hormone and vasopressin, but no change in adrenaline or noradrenaline levels was observed. All these effects were prevented or attenuated when the animals were pretreated intravenously with the cyclo‐oxygenase inhibitor indomethacin (IND; 2 mg/kg). Similarly, in pigs (n = 3 per treatment) given IND, LPS or IND + LPS, parallel changes in the neuronal expression of c‐Fos were observed in hypothalamic regions concerned with thermoregulation, neurohypophysial secretion, and the control of pituitary‐adrenocortical function. The stimulatory action of LPS in the median preoptic, supraoptic and paraventricular nuclei was prevented by IND, whereas IND given alone was without effect. These findings suggest that inducible cyclo‐oxygenase pathways are responsible for the febrile and neuroendocrine effects of endotoxin in this species. © 1995 The Physiological Society