[Microbore high performance liquid chromatographic method for measuring acetylcholine and choline in microdialysates...

Acetylcholine (Ach) and choline (Ch), two important neurotransmitters, in vivo microdialysates obtained from hippocampus and frontal cortex of rats were measured by microbore high performance liquid chromatography with electrochemical detection combined with a post-column immobilized enzyme reactor. Good linear relationships (r2 = 0.990 and 0.991) between the concentration (10 - 2 000 nmol/L) of Ach and Ch injected onto the column and peak height were found. The levels of Ach and Ch were found the highest during the period of wakefulness, and became increasingly lower during anesthetized periods due to the increased concentrations of inhaled isoflurane. Good correlation between the decrease in concentration of Ach in hippocampus and frontal cortex of rats and the concentration of inhaled isoflurane was found (P < 0.05). The results indicate that isoflurane induced a dose-dependent decrease in concentration of Ach in the rat hippocampus and frontal cortex.