Comparison of anorectic drugs in rats trained to discriminate between satiation and deprivation

The motivation produced by morphine and food is isomorphic: Approaches to specific motivational stimuli are learned

“…Through this association in time between the attenuation of the perceptual cues of hunger and food consumption, the perceptual effects of food deprivation may come to act as powerful discriminative cues for appetitive responses to food. Interestingly, in contrast to earlier failed attempts to condition an instrumental response to an internal cue derived from states of deprivation (Bolles, 1975;Webb, 1955), numerous studies have recently demonstrated that the intensity of food deprivation can indeed produce discriminative cues that can control instrumental responses (Capaldi & Davidson, 1979;Capaldi, Viveiros, & Davidson, 1981;Corwin, Woolverton, & Schuster, 1990;Schechter, 1990), as well as enter into Pavlovian conditional discriminations (Davidson, 1987;Davidson, Flynn, & Jarrard, 1992). Perhaps environmental cues that come to condition feeding behavior (Weingarten, 1985) do so by eliciting the discriminative effects of food deprivation.…”

“…Given that the discriminative and motivational effects of stimuli are not isomorphic but dissociable (Berridge et aI., 1989;Martin et al, 1991), then drugs may alleviate the motivational, but not the discriminative, effects of hunger. Amphetamine has strong anorexic effects, but minimal, if any, ability to substitute for the perceptual effects of food in a food-deprived animal (Corwin et aI., 1990;Schechter, 1990). Therefore, the alleviation of the discriminative effects induced by food deprivation would be specifically correlated only with food ingestion.…”