Circadian regulation of dentate gyrus excitability mediated by G-protein signaling

The central circadian regulator within the suprachiasmatic nucleus transmits time of day information by a diurnal spiking rhythm that is driven by intrinsic activity of molecular clock genes controlling membrane excitability. Most brain regions, including the hippocampus, harbor similar intrinsic circadian transcriptional machinery but whether these molecular programs generate oscillations of membrane properties is unexplored. Here, we show that intrinsic excitability of mouse dentate granule neurons exhibits a 24-hour oscillation that controls spiking probability. Diurnal changes in excitability are mediated by antiphase G-protein regulation of potassium and sodium conductances to reduce excitability during the light phase. Disruption of the circadian transcriptional machinery by conditional deletion of Bmal1 enhances excitability selectively during the light phase, increasing engram recruitment and spatial discrimination memory. These results reveal that circadian transcriptional machinery regulates intrinsic excitability, highlighting the role of cell-autonomous oscillations in hippocampal function and behavior. HighlightsDentate neurons exhibit a 24-hour oscillation of excitability with low excitability during the Light phase Reduced excitability results from G-protein regulation of passive and active properties Bmal1 deletion disrupts G-protein regulation to enhance excitability during the Light Bmal1 deletion enhances the size of memory engrams and spatial discrimination