Carbachol-induced β oscillations in three regions of rat hippocampal slices

The carbachol-induced β oscillation was studied using rat hippocampal slices. With the application of carbachol or carbachol and 5 μM bicuculline, the oscillations with the β frequency range of 13–20 Hz were recorded from the CA3, CA1 and dentate gyrus (DG) region. Previous results indicated that the generator of β oscillation is located in the CA3 region. In the present study, we observed the β oscillation in CA3 when we cut off the Schaffer collateral and/or mossy fiber. The frequency of β oscillation decreased when we cut off both Schaffer collateral and mossy fiber, compared with the frequency observed in the intact hippocampal slice. The β oscillation was not changed when we cut off only Schaffer collateral. The pattern of β oscillation changed to the individual field activity when we cut off only the mossy fiber. These results suggest that the CA3 can receive the input from both CA1 and DG through the putative recurrent projection and mossy fiber.