L-dopa-induced air-stepping in preweanling rats. I. Effects of dose and age.

The effects of several doses of L-DOPA (25, 50, 75 and 100 mg/kg) on air-stepping were studied in rats on the day of birth and on 5, 10, 15 and 20 days of age. Occurrence of air-stepping increased and latency to air-stepping generally decreased with dose except at 10 days of age; duration of air-stepping increased with increasing dose of L-DOPA at every age. The occurrence of a variety of air-stepping gaits was age-dependent. On the day of birth, air-stepping consisted primarily of episodes of forelimb alternation; on days 5-20, diagonal progression was the predominant gait, but beginning at day 10, episodes of air-swimming, air-galloping and other locomotor patterns were interspersed. Not only could the durations of most of these gaits be increased with increasing dose of L-DOPA, but at some ages, increasing the dose of L-DOPA led to gait changes.