Apomorphine anorexia: the role of dopamine receptors in the ventral forebrain.

The inhibition of feeding following the administration of apomorphine, systemically or directly into the nucleus accumbens/ventral striatum, was studied using a microstructural analysis paradigm. On systemic administration, apomorphine reduced food consumption, eating rate and eating time; the effects were blocked by sulpiride but not by SCH-23390. Two doses of apomorphine were administered centrally. Both doses reduced total food intake and eating rate; only the higher dose also reduced eating time; all of these effects were blocked by sulpiride pretreatment. Only the lower dose reduced locomotor activity and rearing in the open field. The results suggest that apomorphine reduces eating rate by an action on dopamine (DA) axon terminal autoreceptors. We have previously demonstrated that apomorphine reduces eating time by an action on DA cell body autoreceptors. Therefore, the two populations of DA autoreceptors appear to be differentially involved in behaviour.