Effect of cholecystokinin octapeptide on body temperature in the rat

The C-terminal octapeptide of cholecystokinin (CCK-8) injected into the lateral ventricle of rats produced a lowering of body temperature. CCK-8 potentiated pentobarbital-induced hypothermia, but not the ethanol one. Thyrotropin releasing hormone (TRH) and prostaglandin E2 (PGE2) antagonized the hypothermic effect of CCK-8. Non-sulfated CCK-8 was ineffective in lowering body temperature, indicating that sulfated tyrosine in the CCK molecule is indispensable for its hypothermic action. Caerulein was found to possess rather less activity compared with CCK-8.