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Zusammenfassung:
Acetylcholine (Ach) is believed to play a major role in attentional processing in cortex, thereby contributing
to memory formation and maintenance. To understand its role in these neuronal processes, we set out to
monitor ACh level-changes in prefrontal cortex of a monkey performing a delayed match to sample task. The
changes were monitored during a phase of rest and during the task to compare the baseline level of Ach with
the level during task. We used a push and pull method to sample extracellular brain fluid (EBF) from the
prefrontal cortex (PFC) at very low flow rates, low nanol/min range. These flow rates were chosen to reduce
the depletion of the neuronal environment in contrast to the conventionally used microdialysis. After the
sampling of the EBF, the capillary, where the EBF samples were stored, was directly coupled to capillary high
performance liquid chromatography-mass spectrometry (HPLC-MS) for the chemical analysis to detect and
quantify ACh. The combination of the sampling and the analysis system proofed possible to determine
amounts of Ach in the attomole range from the EBF samples. In the experiments a 7-min interval was chosen
to monitor the Ach changes during rest and the task. We could reliably detect and quantify Ach concentrations
during rest and the delayed match to sample task, showing a significant increase in Ach concentration during
the task. Our results show clearly the involvement of acetylcholine in behaving monkeys involved in a
delayed match to sample task, where memory formation and attention are mandatory for the appropriate
performance during the task.