The actions of individual
urocortins on colon temperature were studied in rats.
Urocortin 1,
urocortin 2 or
urocortin 3 was injected into the lateral brain ventricle in conscious rats and the colon temperature was measured at different times following injection, for up to 6 h. In order to study the possible role of
prostaglandins, the animals were treated with either a
urocortin together with the
pyrazolone derivative
noraminophenazone to inhibit the action of
cyclooxygenase in initiating
hyperthermia, or with
noraminophenazone 30 min following
urocortin administration to act on existing
hyperthermia.
Noraminophenazone was administered intramuscularly in a dose of 50 mg/kg.
Urocortin 1 caused a dose-related increase in colon temperature, maximal action being observed at a dose of 2 microg with the maximal increase in body temperature at 4 h.
Noraminophenazone prevented the
urocortin-induced increase in colon temperature and attenuated the already existing elevated body temperature. Somewhat similar action was observed with
urocortin 2. However, following treatment with 0.5 or 1.0 microg
urocortin 2, the action was already over at 2 h, whereas 2 microg increased the colon temperature steadily, with a maximum at 4 h.
Noraminophenazone blocked or diminished the action of
urocortin 2.
Urocortin 3 in a dose of 1 microg was the most effective in increasing the colon temperature; the maximal effect was observed at 2 h.
Noraminophenazone blocked the development of
urocortin 3-induced
hyperthermia, or attenuated it when the
hyperthermia was already present. The results demonstrated that
urocortin 1, 2 or 3 caused increases in body temperature when injected into the lateral brain ventricle, though the optimal dose and the duration of
hyperthermia differed for the individual
urocortins. The
cyclooxygenase inhibitor blocked or diminished the action of these
urocortins, indicating the involvement of
prostaglandins in
urocortin-
induced hyperthermia.