Biomedical subjects

A E Sickles

Publications and source records attributed to A E Sickles.

3 recordsLinked to original sources

PubMed1994

Noradrenergic alpha-1 and alpha-2 antagonists block L-dopa-induced air-stepping in neonatal rats.

Five-day-old rat pups suspended in air and administered L-3,4-dihydroxyphenylalanine (L-DOPA) engage in a highly stereotyped and coordinated locomotor behavior termed air-stepping. L-DOPA is a precursor for dopamine and noradrenaline and one or both of these neurotransmitters could play a role in L-DOPA-induced air-stepping. The role of noradrenaline was investigated by assessing the abilities of the alpha-1 noradrenergic receptor antagonist prazosin and the alpha-2 noradrenergic receptor antagonist idazoxan to block L-DOPA-induced air-stepping in 5-day-old rats. Both antagonists decreased the duration of air-stepping. In addition, prazosin altered the topography of air-stepping by interfering with coordination of the hindlimbs. The results suggest that alpha-1 and alpha-2 noradrenergic receptor subtypes are involved in L-DOPA-induced air-stepping.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1992

Dopamine D1 and D2 antagonists block L-dopa-elicited air-stepping in neonatal rats.

When administered to rat pups that have been suspended in air, L-3,4-dihydroxyphenylalanine (L-DOPA) induces a highly stereotypic locomotor response referred to as air-stepping. In order to determine the respective roles of dopamine D1 and D2 receptors in the expression of air-stepping, the abilities of the selective D1 antagonist SCH 23390 and the selective D2 antagonist spiperone to block L-DOPA-induced air-stepping in 5-day-old rat pups were assessed. Both antagonists increased latency to onset, and both decreased total duration of air-stepping by decreasing the number and length of air-stepping episodes. Neither SCH 23390 nor spiperone altered the topography of the air-stepping response; however, subjects receiving lower doses of spiperone spent significantly more time with the body dorsiflexed and limbs extended (extension/tremor activity) than did control subjects. The results suggest that both the D1 and D2 receptor subtypes are involved in the production of L-DOPA-induced locomotor activity.

Animals↗

PubMed1991

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.

Animals↗