DA₁ receptor activity opposes anorectic responses to amino acid-imbalanced diets

The serotonin₃ (5-HT₃) receptor plays an important role in the aminoprivic feeding model. Other neurochemical systems, including cholecystokinin (CCK) and dopamine (DA), are known to affect food intake. We pretreated rats systemically with tropisetron, a 5-HT₃ receptor antagonist, alone and combined with antagonists of DA₁ and DA₂ receptors, and measured intake of an amino acid-imbalanced diet (IMB). As expected, tropisetron significantly increased intake of IMB. SCH-23390, a DA₁ antagonist, increased IMB anorexia. When combined with tropisetron, DA₂ antagonism with eticlopride reduced short-term intake of both the basal diet (BAS) and IMB. In the IMB model, specificity of 5-HT₃-DA₂ interactions, and of 5-HT₃-CCK(A) interactions from previous studies, prompted investigation of CCK(A)-DA₂ interactions; there appeared to be none. SKF-38393, a DA₁ agonist, combined with the CCK(A) receptor antagonist, devazepide, increased BAS and tended to increase IMB intake. Thus, CCK(A)-DA₁ interactions were not specific for IMB. These data suggest that DA₁ receptor activity opposes IMB anorexia, possibly via an interaction with the 5-HT₃ receptor. Copyright (C) 1999 Elsevier Science Inc.