Feeding stimulated by very low doses of d-amphetamine administered systemically or by microinjection into the striatum

The effects of d-amphetamine over a wide range of doses (0.125-4.0 mg/kg IP) on rat unconditioned behaviour were examined in the presence of food and water (experiment 1), in their absence (experiment 2) and after microinjection (2.0 μg in 0.5 μl) directly into the striatum (experiment 3). In experiment 1 very low doses (0.125 and 0.25 mg/kg) stimulated the intake of food, but not water, and higher doses produced locomotor hyperactivity, rearing, stereotyped sniffing and anorexia. In experiment 2 all doses, including very low doses (0.125 and 0.25 mg/kg), significantly potentiated locomotor activity. In experiment 3, microinjection into the corpus striatum elicited substantial feeding, but not drinking, locomotor activity or stereotyped behaviour. The results suggest that a single graded facilitative mechanism underlies the effects on food intake and other behavioural effects of amphetamine, as implied by a general hypothesis of amphetamine action proposed in the literature, and that these effects may to a large extent by mediated by forebrain dopamine systems.