Ceruletide inhibits water intake in deprived mice: Comparison with morphine and the enkephalin analogue, FK 33-824

Subcutaneous injections of ceruletide (caerulein diethylammonium hydrate, CER) reduced dose-dependently the water intake in male NMRI mice deprived of water for 18 h. The ED 50 for this effect was 5.5 (3.70–7.94) nmol/kg, which is 3.7 times more than the corresponding food intake inhibiting dose. Also inhibitory but much less potent than CER were (in decreasing order) FK 33–824, morphine and naloxone. Naloxone was an antagonist to both FK 33–824 and morphine but not to CER, thereby separating CER from the opioids. When water intake reducing doses of CER (15 nmol/kg) and FK 33–824 (850 nmol/kg) were combined, the two peptides were not additive but antagonized each other. Together, the present and previous results suggest that pharmacological inhibition of food and water intake have different characteristics.