Effect of sulpiride on amphetamine-induced activity and stereotyped locomotion

To investigate the hypothesis that sulpiride potentiates stereotyped locomotion at an intermediate dose of amphetamine, rats were assigned to one of four treatment groups (n=7 per group): vehicle + saline; 20 mg/kg sulpiride + saline; vehicle + 3.5mg/kg amphetamine; 20 mg/kg sulpiride + 3.5 mg/kg amphetamine. An automated tracking system was used to record distance moved and sequences of movements between quadrants in a circular open-field. The results showed that amphetamine increased horizontal distance moved, and increased the number and proportion of thigmotaxic trips around the perimeter of the apparatus. Sulpiride reduced amphetamine-induced hyperactivity and the number of perimeter trips, but had no effect on the proportion and maximum run length of perimeter trips. Thus sulpiride reduces the hyperactivity produced by an intermediate dose of amphetamine, but does not appear to affect the stereotyped nature of locomotion under the drug.