A method allowing intracellular and extracellular single-unit recordings from brain slices in the grease-gap chamber

The grease-gap chamber makes it possible to perfuse two parts of a brain slice separately. Hence, it lies between bath application and iontophoresis or pressure ejection in terms of the size of the region that receives controlled drug dosing. Modifications of a commercially available chamber are described which have permitted the first extracellular and intracellular single-unit recordings to be taken from brain slices in a grease-gap preparation. In addition, we describe the electrical resistance of the gap as a measure of the integrity of the barrier and a simple method for monitoring this resistance continuously. The resistance monitor is particularly useful during low flow rate conditions that improve mechanical stability. These techniques extend the grease-gap method to electrophysiological studies of single cells in slices.