Development of a method to evaluate glutamate receptor function in rat barrel cortex slices

The rat is a nocturnal animal and uses its vibrissae extensively to navigat e its environment. The vibrissae are linked to a highly organized part of t he sensory cortex, called the barrel cortex which contains spiny neurons th at receive whisker specific thalamic input and distribute their output main ly within the cortical column. The aim of the present study was to develop a method to evaluate glutamate receptor function in the rat barrel cortex. Long Evans rats (90 - 160g) were killed by cervical dislocation and decapit ated. The brain was rapidly removed, cooled in a continuously oxygenated, i ce-cold Hepes buffer (pH 7.4) and sliced using a vibratome to produce 0.35m m slices. The barrel cortex was dissected from slices corresponding to 8.6 to 4.8mm anterior to the interaural line and divided into rostral, middle a nd caudal regions. Depolarization-induced uptake of Ca-45(2+) was achieved by incubating test slices in a high K+ (62.5mM) buffer for 2 minutes at 35 degreesC. Potassium-stimulated uptake of Ca-45(2+) into the rostral region was significantly lower than into middle and caudal regions of the barrel c ortex. Glutamate had no effect. NMDA significantly increased uptake of Ca-4 5(2+) into all regions of the barrel cortex. The technique is useful in det ermining NMDA receptor function and will be applied to study differences be tween spontaneously hypertensive rats (SHR) that are used as a model for at tention deficit disorder and their normotensive control rats.