M1 ACETYLCHOLINE-RECEPTOR STIMULATION INCREASES THE EXTRACELLULAR CONCENTRATIONS OF GLUTAMATE AND GABA IN THE MEDIAL PREFRONTAL CORTEX OF THE RAT

The present study was undertaken to examine the effects of different m uscarinic receptor agonists on glutamate and GABA concentrations in th e medial prefrontal cortex of the rat. In vivo perfusions were made in the conscious rat using a concentric push-pull cannulae system. Amino acid concentrations in samples were determined by HPLC with fluoromet ric detection. The intracortical perfusion of arecoline, a M1-M2 musca rinic receptor agonist, produced a significant increase in extracellul ar [GLU] and [GABA]. McN-A-343, a M1 muscarinic receptor agonist, but not the M2 muscarinic receptor agonist, oxotremorine, produced a signi ficant increase in extracellular [GLU] and [GABA]. The effects of McN- A-343 on extracellular [GLU] and [GABA] were blocked by pirenzepine, a M1 muscarinic receptor antagonist. These results suggest that M1 musc arinic receptor stimulation increases the extracellular concentrations of GLU and GABA in the medial prefrontal cortex of the rat.