Psychomotor stimulants, social deprivation and play in juvenile rats

Treatment with d-amphetamine (0.125-1 mg/Kg) or methylphenidate (0.5-4 mg/kg caused dose-dependent decreases in play fighting in juvenile rats which were independent of sex and strain. Although brief social isolation profoundly increased play fighting, qualitatively similar drug effects on play were observed in socially housed and isolated animals. By contrast, at the highest doses tested both amphetamine and methylphenidate increased social investigation, but only if the rats were socially isolated. Stimulation of catecholamine systems is evidently incompatible with the expression of playful behavior.