The involvement of methysergide-sensitive receptors and prostaglandins in the hyperthermia evoked by 5-HT in the cat.

In the unanesthetized cat, an injection of 0.01 or 0.03 M 5-hydroxytryptamine into the rostral hypothalamus produced an immediate, short-lasting increase or decrease in body temperature. A delayed and long-lasting hyperthermia often followed the initial response. When indomethacin, 10 mg/kg, was administered intraperitoneally 3 hours prior to an injection of 5-hydroxytryptamine at sites which produced an initial increase in body temperature, the secondary hyperthermia was reduced or abolished but the immediate response remained undiminished. Pretreatment with methysergide, 2 mg/kg i.p., attenuated or abolished the initial temperature increase but did not reduce the delayed hyperthermia. The results suggest that the initial rise in body temperature produced by 5-hydroxytryptamine is mediated by activation of methysergide-sensitive 5-HT receptors and that the response is independent of prostaglandin release. The secondary hyperthermia, on the other hand, is apparently mediated by a sustained release of prostaglandins.