CCK-A receptor antagonists have selective effects on nutrient-induced foodintake suppression in rats

To provide additional support to the hypothesis that only dietary protein ( Pro; chicken egg albumin) and not amino acids (AA; patterned after albumin) , carbohydrates (CHO; cornstarch), or fats (Fat; corn oil) produces a satia ting effect via CCK receptors, two CCK-A receptor antagonists (PD-140,548 a nd devazepide) were coadministered with each nutrient. Given alone [4 ml in tragastrically (ig)] Pro (1.0 g), AA (1.0 g), CHO (1.4 g), and Fat (2.4 g) suppressed (P < 0.05) food intake on average during the first 2 h of feedin g by 1.4 (36%), 1.5 (48%), 1.0 (33%), and 1.2 g (41%), respectively. Devaze pide (0.5 mg/kg) and PD-140,548 (1.0 mg/kg) given alone increased food inta ke during 0-2 h by 0.7 g (18%) and during 0-1 h by 0.5 g (15%), respectivel y. When coadministered with PD-140,548 (1.0 mg/kg ip), the suppression of f ood intake caused by Pro was modulated during 0-2 h by 57% (Pro X drug inte raction, P < 0.05), but AA-, CHO-, and Fat-induced suppression of feeding w as not affected (nutrient x drug interaction, P > 0.05). Devazepide (0.5 mg /kg ip) did not modulate AA-, CHO-, and Fat-induced food intake suppression during any time period (nutrient x drug interaction, P > 0.05). These stud ies provide additional evidence that CCK-A receptors play a role in Pro (al bumin) but not AA-, CHO (cornstarch)-, or Fat (corn oil)-induced food intak e suppression in rats.