The effect of 4-aminopyridine on the spinal locomotor rhythm induced by L-DOPA.
In high spinal curarized cats rhythmic motor output similar to locomotion ('fictive locomotion') of all 4 limbs was obtained after intravenous application of the noradrenergic precursor, L-DOPA, and nialamide combined with 4-aminopyridine (4-AP). The activity was recorded from muscle nerves. In the presence of 4-AP, which enhances transmission at various excitatory and inhibitory synapses, reduced amounts of DOPA were sufficient to evoke fictive locomotion. 4-AP alone did not elicit locomotion. The burst rate increased up to 6 Hz with the amount of 4-AP given (0.5-50 mg/kg). The cyclic frequency of high spinal cats exhibiting either fictive locomotion or walking on a treadmill was accelerated by 4-AP. After a supplementary transection of the spinal cord at the upper lumbar level both fore- and hindlimbs generally continued to show fictive locomotion with similar frequencies. In the presence of high doses of clonidine (alpha-receptor-activator, greater than 4 mg/kg), the locomotor pattern was replaced by regular (2 Hz) synchronous discharges in all flexors and extensors.
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D004305:Dose-Response Relationship, Drug; D007980:Levodopa / Q000494:pharmacology*; D008124:Locomotion / Q000187:drug effects*; D009068:Movement / Q000187:drug effects*; D009132:Muscles / Q000294:innervation; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology*; D009526:Nialamide / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
D000631:Aminopyridines; D009467:Neuromuscular Depolarizing Agents; D007980:Levodopa; D015761:4-Aminopyridine; D009526:Nialamide