GABA(A) RECEPTOR-INDUCED INHIBITION OF NEURONAL BURST FIRING IS WEAK IN RAT SOMATOSENSORY CORTEX

EXTRACELLULAR and intracellular recordings have been made from the somatosensory cortex of anesthetized rats. From 264 neurons having receptive fields including the contralateral whiskers, we have determined that two distinct patterns of firing are observed, and call these two patterns regular spiking and bursting. Iontophoretically administered gamma-aminobutyric acid (GABA), muscimol, or flurazepam showed significantly weaker inhibition of the bursting pattern of firing than of the regular spiking pattern. By contrast, baclofen inhibited both types of firing to the same extent. These results suggest that intracortical GABA receptor subtypes are involved in different ways in modulating the expression modes of discharge.