Action of GABAB receptor on local network oscillation in somatosensory cortex of oral part: focusing on NMDA receptor.

The balance of activity between glutamatergic and GABAergic networks is particularly important for oscillatory neural activities in the brain. Here, we investigated the roles of GABA receptors in network oscillation in the oral somatosensory cortex (OSC), focusing on NMDA receptors. Neural oscillation at the frequency of 8-10 Hz was elicited in rat brain slices after caffeine application. Oscillations comprised a non-NMDA receptor-dependent initial phase and a later NMDA receptor-dependent oscillatory phase, with the oscillator located in the upper layer of the OSC. Baclofen was applied to investigate the actions of GABA receptors. The later NMDA receptor-dependent oscillatory phase completely disappeared, but the initial phase did not. These results suggest that GABA receptors mainly act on NMDA receptor, in which metabotropic actions of GABA receptors may contribute to the attenuation of NMDA receptor activities. A regulatory system for network oscillation involving GABA receptors may be present in the OSC.