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_B 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_B receptors. The later NMDA receptor-dependent oscillatory phase completely disappeared, but the initial phase did not. These results suggest that GABA_B receptors mainly act on NMDA receptor, in which metabotropic actions of GABA_B receptors may contribute to the attenuation of NMDA receptor activities. A regulatory system for network oscillation involving GABA_B receptors may be present in the OSC.