4-Aminopyridine (4AP) Enhances Acetylcholine Output from the Rat Cerebral Cortex in vivo

Abstract

This chapter discusses a study to analyze the effect of 4-aminopyridine (4AP) administration on cortical acetylcholine (ACh) output. The study was done on adult male Wistar rats under urethane or pentobarbital anesthesia. A small Perspex cylinder filled with eserinized Ringer solution was applied on the exposed cerebral cortex. The solution in the collecting cylinder was removed every 10 min and its ACh content was determined by bioassay on the dorsal muscle of the leech. In urethane anaesthetized rats, the control ACh output was 0.98 ± 0.16 ng/min/cm 2 and the administration of 4AP (3 mg/kg i.p.) was followed by a rapid increase in ACh output lasting at least 40 min. The increase in ACh output was paralleled by a decrease in the depth of anesthesia and at the peak was 244 ± 35% larger than the basal output. In pentobarbital anaesthetized rats, in which ACh basal release was 1.52 ± 0.24 ng/min/cm 2 , 4AP elicited a slow increase in ACh output that 60 min after administration was 3-fold larger than prior administration. However, pentobarbital sleeping time was not modified by 4AP.