Detection and imaging of L-glutamate released from mouse-brain slices with an enzyme-based membrane

A new and simple method for detecting and color imaging of L-glutamate released in mouse-brain slices is described based on an enzyme-coupling reaction. The method utilizes L-glutamate oxidase (GluOx) and horseradish peroxidase (HRP) immobilized in a bovine serum albumin (BSA)-glutaraldehyde matrix on a poly-L-lysine-coated glass cover slip. The enzymes are spontaneously and continuously supplied from the membrane into an extracellular solution of the brain slice placed on the membrane after dipping in a redox substrate (DA-64). The Bindschedler's Green (BG) converted from the DA-64 by the enzyme reaction gives green signals in the brain slice, which are related to the concentration of L-glutamate released in its regions. The first examples of color images for the spatial distribution of L-glutamate in the regions of adult mouse brain slices are demonstrated. The regions where the intense green signals were observed matched the reported distribution of mRNAs encoding the NMDA receptor in the mouse-brain slice.