PROSTAGLANDIN-DEPENDENT C-FOS EXPRESSION IN THE MEDIAN PREOPTIC NUCLEUS OF PIGS SUBJECTED TO RESTRAINT - CORRELATION WITH HYPERTHERMIA

Restraint using a nose snare activates the hypothalamo-pituitary-adrenocortical axis and induces c-Fos expression in the paraventricular hypothalamus in the pre-pubertal pig; this procedure also induces hyperthermia in pigs. To investigate the neural mechanisms involved in this thermoregulatory response, c-Fos protein was quantified in the forebrains of pigs snared for 15 min (n = 5), injected with saline vehicle via an i.v. catheter (controls, n = 4) or treated with the cyclooxygenase inhibitor, indomethacin (2 mg/kg i.v.), prior to a 15 min period of snaring (n = 3). There were few c-Fos immunopositive nuclei in the median preoptic nucleus of non-stressed animals. By contract, c-Fos expression in this region was enhanced by snaring (P < 0.001) and this response was markedly reduced (P < 0.002) by indomethacin. The results suggest that restraint induces a prostaglandin-mediated increase in core temperature (stress hyperthermia) in the growing pig that involves the activation of preoptic thermoregulatory neurons.