Multiple tooth-losses during development suppress age-dependent emergence of oscillatory neural activities in the oral somatosensory cortex.

Tooth and tooth-related organs play important roles in not only mastication, but also sensory perception in the oral region. In general, sensory neural inputs during the developmental period are required for the maturation of functions in the sensory cortex. However, whether maturations of oral somatosensory cortex (OSC) require certain levels of sensory input from oral regions has been unclear. The present study investigated the influence of multiple tooth-losses during the developmental period on age-dependent emergence of rhythmic activities of population neurons in the OSC. Low-frequency electrical stimulation was delivered to layer IV and field potentials were recorded from layer II/III in the OSC of rat brain slices. In control rats, N-methyl-d-aspartate (NMDA) receptor-dependent oscillation at 8-10 Hz appeared during postnatal weeks 2-3. In rats with extraction of multiple teeth at 17-18 days old, oscillation did not appear even at maturity, whereas in rats with multiple teeth extracted at 37-38 days old, oscillation appearances were maintained in maturity. Thus, emergence of oscillation in the OSC was suppressed by multiple tooth-losses during postnatal 2-3 weeks. These results suggest that sufficient neural inputs from the teeth and tooth-related organs during developmental periods are essential for maturation of neural functions in the OSC.