CCK-A receptor antagonists have selective effects on nutrient-induced food intake 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 satiating effect via CCK receptors, two CCK-A receptor antagonists (PD-140,548 and devazepide) were coadministered with each nutrient. Given alone [4 ml intragastrically (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 feeding by 1.4 (36%), 1.5 (48%), 1.0 (33%), and 1.2 g (41%), respectively. Devazepide (0.5 mg/kg) and PD-140,548 (1.0 mg/kg) given alone increased food intake during 0-2 h by 0.7 g (18%) and during 0-1 h by 0.5 g (15%), respectively. When coadministered with PD-140,548 (1.0 mg/kg ip), the suppression of food intake caused by Pro was modulated during 0-2 h by 57% (Pro X drug interaction, P < 0.05), but AA-, CHO-, and Fat-induced suppression of feeding was 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 studies provide additional evidence that CCK-A receptors play a role in Pro (albumin) but not AA-, CHO (cornstarch)-, or Fat (corn oil)-induced food intake suppression in rats.