Sucrose sham-feeding in the rat after administration of the selective dopamine D2 receptor agonist N-0437, d-amphetamine or cocaine

Drugs which act as agonists at dopamine receptors, or which increase dopamine release (e.g., d-amphetamine, cocaine) are known to reduce food intake. The present experiments investigated, for the first time, the effects of a highly selective dopamine D2 receptor agonist, N-0437 (0.3-3.0 mg/kg, IP), on 5% sucrose sham-feeding in gastric fistulated rats, and compared these results with those of d-amphetamine (0.1-3.0 mg/kg, IP) and cocaine (3.0-10.0 mg/kg, IP). The results showed that sucrose sham-feeding was resistant to the effects of N-0437, even though the D2 agonist dose-relatedly reduced sucrose real-feeding in intact animals. The two psychomotor stimulants, d-amphetamine and cocaine, produced some reductions in sham-feeding, although in the case of the highest dose of d-amphetamine, the pronounced reduction in the consumption of sucrose was probably secondary to induced behavioral stereotypy. The results suggest that D2 receptor stimulation may interact with satiety cues to reduce ingestion of sucrose, but that in the absence of potent satiety stimuli D2 receptor stimulation is ineffective. Furthermore, N-0437 appeared not to be equivalent to either d-amphetamine or cocaine in their effects to reduce sucrose sham-feeding.