L-dopa-induced air-stepping in developing rats.
Rat pups at postnatal day (PN) 0, 5, 10, 15, and 20 were injected with 100 mg/kg L-3,4-dihydroxyphenylalanine (L-DOPA; s.c.) or the control vehicle and suspended in a sling. L-DOPA induced highly stereotyped air-stepping that varied along several dimensions across development. The latency to air-stepping was constant across age, but the duration was significantly shorter in the older pups. At all ages, air-stepping was preceded or accompanied by raising of the head and dorsiflexion of the tail. The rate of stepping increased across age and gait varied with age. At PN 0, L-DOPA induced alternating forelimb movements with little involvement of the hindlimbs. At PN 5 and 10, both forelimb and hindlimb alternation were observed. At PN 10 and 15 swimming-like behavior emerged, and at PN 10, 15, and 20, episodes of galloping were interspersed with limb alternation. Thus, highly coordinated activity can be elicited by L-DOPA at all ages studied when the rat pup needs not support its own body weight and has no contact with a substrate. Drug-induced air-stepping promises to be an important new paradigm for pharmacological and behavioral studies of the development of locomotor controls in mammals.
Van Hartesveldt
C
C
Psychology Department, University of Florida, Gainesville 32611.
Sickles
A E
AE
Porter
J D
JD
Stehouwer
D J
DJ
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000502:physiology; D005684:Gait; D007980:Levodopa / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014743:Videotape Recording
D007980:Levodopa