Monitoring cellular release with dynamic channel electrophoresis

A channel electrophoresis system consisting of a 50 μm by 75 mm by 25 mm separation channel has been adapted to follow stimulated release from individual and small groups of isolated neurons. The cells of interest are placed in a nanoperfusion chamber located near the exit of a sampling capillary. The capillary is scanned across the mouth of the channel so that compounds released from the cells are dynamically introduced into the separation channel. The position of the sampling capillary along the channel entrance yields temporal information, and electrophoresis in the channel length dimension provides the chemical data. NDA/CN^- is placed in the inlet vial between the sampling capillary and channel so that primary amine-containing compounds released from the cell are derivatized prior to separation as they enter the channel. The performance of this method is evaluated, and the optimum NDA/CN^- concentration and separation conditions for this on-line derivatization are presented, with detection limits for most underivatized amino acids of ∼500 nM at a particular time slice. The time-resolved electropherograms from single and a small group of cerebral ganglion neurons from Aplysia californica stimulated with KCl show multiple components released with different time courses.