Co-activation of nAChR and mGluR induces [gamma] oscillation in rat medial septum diagonal band of Broca slices

To examine whether co-activation of nAChR and mGluR1 induced γ oscillation (20-60 Hz) in rat medial septum diagonal band of Broca (MSDB) slices. Rat brain sagittal slices containing the MSDB were prepared. Extracellular field potentials were recorded with glass microelectrodes. The nAChR and mGluR1 agonists were applied to the slices to induce network activity. Data analysis was performed off-line using software Spike 2. Co-application of the nAChR agonist nicotine (1 μmol/L) and the mGluR1 agonist dihydroxyphenylglycine (DHPG, 25 μmol/L) was able to induce γ oscillation in MSDB slices. The intensity of nAChR and mGluR1 activation was critical for induction of network oscillation at a low ([thetas] oscillation) or high frequency (γ oscillation): co-application of low concentrations of the two agonists only increased the power and frequency of oscillation within the range of [thetas], whereas γ oscillation mostly appeared when high concentrations of the two agonists were applied. Activation of mGluR1 and nAChR is able to program slow or fast network oscillation by altering the intensity of receptor activation, which may provide a mechanism for modulation of learning and memory.