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

The serotonin(3) (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 DA(1) and DA(2) receptors, and measured intake of an amino acid-imbalanced diet (IMB). As expected, tropisetron significantly increased intake of IMB. SCH-23390, a DA(1) antagonist, increased IMB anorexia. When combined with tropisetron, DA(2) antagonism with eticlopride reduced short-term intake of both the basal diet (BAS) and IMB. In the IMB model, specificity of 5-HT3-DA(2) interactions, and of 5-HT3-CCKA interactions from previous studies, prompted investigation of CCKA-DA(2) interactions; there appeared to be none. SKF-38393, a DA(1) agonist, combined with the CCKA receptor antagonist, devazepide, increased BAS and tended to increase IMB intake. Thus, CCKA-DA(1) interactions were not specific for IMB. These data suggest that DA, receptor activity opposes IMB anorexia, possibly via an interaction with the 5-HT3 receptor. (C) 1999 Elsevier Science Inc.