Rapid chemical sampling of endogenous species from brain slice preparations.

A very simple method of chemical sampling from the surface of brain slices is described. This procedure utilizing micropipets involves no sample dilution, and thus has very high sensitivity. Basal and stimulated concentrations of neurotransmitters and their metabolites are sampled from a thin fluid layer on the slice surface and appear to be in mobile equilibrium with the brain slice extracellular fluid levels. Rapid sampling allows one to follow the time course of stimulated release and reuptake phenomena.