Effects of "anorexia" in appetitive and consummatory behavior.

Abstract

In order to assess the effects of anorexigenic agents on appetitive and consummatory behavior, rats were given sweetened milk either in a bottle or by infusion through an intraoral cannula. In the first experiment, amphetamine (AMP; 0, 0.25, 0.5, and 1 mg/kg) had no effect on the intake of cannula-fed rats but suppressed the intake of bottle-fed rats at the highest two doses. Although increased activity was observed at the highest dose, bottle-fed rats drank less than cannula-fed rats at each dose of the drug. Fenfluramine (FEN; 0, 2.5, 5, and 10 mg/kg) produced a dose-dependent decrease in intake with both methods of feeding, but the effect was greater in bottle-fed rats. Although FEN had marked sedative effects at the highest two doses, bottle-fed rats drank less than cannula-fed rats at each dose of the drug. In a second experiment, cannula- and bottle-fed rats were given milk adulterated with various concentrations of quinine hydrochloride (QHCl; 0, 0.0025, 0.005, 0.01, and 0.02%). QHCl had no effect on the intake of cannula-fed rats but decreased the intake of bottle-fed rats at the highest two concentrations. In a final experiment, the effect of AMP (1 mg/kg) was assessed in a conditioned aversion paradigm. Rats were given four conditioning trials in which access to a 0.1% sodium saccharin solution was followed by an injection of AMP. Again, bottle-fed rats showed greater suppression of intake than cannula-fed rats. Taken together, these results demonstrate that anorexigenic drugs affect appetitive behavior more than consummatory behavior. The implications of these findings for understanding the mechanism of behavioral tolerance are discussed.