Depletion of noradrenaline in the hypothalamus reduces the febrile responses induced by prostaglandin E2, thyrotropin-releasing hormone and beta-endorphin in rats.
The effects of pretreatment of rats with an intrahypothalamic injection of 6-hydroxydopamine on the thermal responses induced by intrahypothalamic injection of noradrenaline, prostaglandin E2, thyrotropin-releasing hormone or beta-endorphin were assessed. Administration of either noradrenaline (2-10 micrograms), prostaglandin E2 (10-40 ng), thyrotropin-releasing hormone (0.5-2.0 micrograms) or beta-endorphin (1-3 micrograms) into the preoptic anterior hypothalamus caused a dose-dependent rise in rectal temperature in conscious rats at an ambient temperature of 22 degrees C. In addition, it was found that three intrahypothalamic doses of 10 micrograms of 6-hydroxydopamine at intervals of 2 days caused a significant depletion of noradrenaline in the hypothalamus to 26.4% of control while the concentration of dopamine in the hypothalamus was not significantly reduced at 95.3% of control. Furthermore, the hyperthermic responses induced by prostaglandin E2, thyrotropin-releasing hormone, or beta-endorphin were greatly attenuated after selective depletion of noradrenaline in the hypothalamus in rats. However, selective depletion of noradrenaline did not affect the noradrenaline-induced hyperthermic responses. The data indicate that either prostaglandin E2, thyrotropin-releasing hormone or beta-endorphin may act through the endogenous release of noradrenaline from the hypothalamus to induce hyperthermic responses in rats.
D000818:Animals; D015232:Dinoprostone; D004298:Dopamine / Q000378:metabolism; D004723:Endorphins / Q000494:pharmacology*; D005334:Fever / Q000139:chemically induced*; D006892:Hydroxydopamines / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D016627:Oxidopamine; D011458:Prostaglandins E / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D001615:beta-Endorphin
D004723:Endorphins; D006892:Hydroxydopamines; D011458:Prostaglandins E; D013973:Thyrotropin-Releasing Hormone; D001615:beta-Endorphin; D016627:Oxidopamine; D015232:Dinoprostone; D004298:Dopamine; D009638:Norepinephrine