Antagonism of 4-aminopyridine on the central nervous system depressant effects of scopolamine in rabbits

Injection of scopolamine 6 mg/kg into the lateral ventricle of brain in rabbits inhibited the righting reflex, the time of recovery to righting being 43± (SD) 6 min; when the icv injection of scopolamine was followed by iv 4-aminopyridine (4-AP) 0.75mg/kg, the recovery time was only 11±3 min (P＜0.01). Icv scopolamine 1.0-1.5 mg/kg to conscious rabbits provoked high-amplitude slow waves, depressed arousal response in electrocorticogram. Subsequent iv 4-AP 0.75-1.0mg/kg converted the high-amplitude slow waves to low-amplitude fast waves and in most cases also restored the arousal response. It appears that 4-AP can antagonize the blocking effect of anticholinergic agents on certain ACh receptors in the CNS just as it dose in peripheral nervous system.