Cholecystokinin octapeptide, caerulein and caerulein analogues: effects on thermoregulation in the mouse.

Cholecystokinin octapeptide (CCK-8), caerulein and seven out of ten analogues of caerulein produced in mice, after subcutaneous administration, a dose-dependent drop in rectal temperature. For the hypothermic effect, i.e. a decrease in temperature by at least 1.5 degree C, ED50's were estimated with these peptides and with morphine, haloperidol and chlorpromazine. Caerulein was most potent, having an ED50 of 4.6 nmol/kg. With the aid of naloxone, atropine, phenytoin and desipramine the hypothermic effect of caerulein could be separated from that of morphine and haloperidol. These experiments, together with those on the relationship between chemical structure and effect, led to the conclusion that the thermoregulatory action of CCK-like peptides may be independent from other central actions, and vice versa.