CCK(A) and 5-HT3 receptors interact in anorectic responses to amino acid deficiency

Serotonin3 (5-HT3) receptors in the periphery mediate anorectic responses to the amino acid deficiency, which occurs after eating amino acid-imbalanced diets (IMB). However, other neurochemical systems, notably cholecystokinin (CCK), are known to affect food intake. We pretreated rats systemically with tropisetron, a 5-HT3 receptor antagonist, alone and combined with antagonists of CCK(A) and CCK(B) receptors, and measured intake of an IMB. Devazepide, a CCK(A) receptor antagonist, appeared to interact with tropisetron in the anorectic responses to IMB, blunting the usual remediation of IMB anorexia by tropisetron. The CCK(B) receptor antagonist, L-365, 260, increased intake of both IMB and an amino acid-balanced basal diet (BAS) and did not interact with tropisetron. Our data suggest that activation of CCK(A) receptors is interactive with 5-HT3 receptor activity in mediating IMB anorexia in the aminoprivic feeding model.