The development of locomotor response to d- and l-amphetamine in the infant mouse

Abstract

To study the possible role of catecholaminergic processes underlying the exaggerated expression of behavioral arousal during early development in the mouse, the locomotor activity of 10-to 12-day-old mice following d-amphetamine injection was recorded over a 5-h period in a shuttlecage apparatus. Reliable effects of a 1-mg/kg dose of d-amphetamine were observed only in the oldest age group. The relative influences of d-and l-amphetamine were then assessed at this age . The stereoisomers were approximately equipotent in elevating activity above saline control levels and demonstrated comparable latency and duration of effects. The results support the notion that heightened arousal at this age is mediated by a nor adrenergic system.