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-dihydrox yphenylalanine (L-DOPA) engage in a highly stereotyped and coordinated locomotor behavior termed air-stepping. L-DOPA is a precursor for dop amine and noradrenaline and one or both of these neurotransmitters cou ld play a role in L-DOPA-induced air-stepping. The role of noradrenali ne was investigated by assessing the abilities of the alpha-1 noradren ergic receptor antagonist prazosin and the alpha-2 noradrenergic recep tor 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 interferi ng with coordination of the hindlimbs. The results suggest that alpha- 1 and alpha-2 noradrenergic receptor subtypes are involved in L-DOPA-i nduced air-stepping.