Firing dynamics of neocortical pyramidal cells and interneurons in nonREM sleep
01/29/2020
Bordé S1, Averkin RG1, Horváth J1, Dashkovskyi V1, Bozsó B1, Szemenyei V1, Tamás G.1
1 MTA-SZTE Research Group for Cortical Microcircuits, Department of Phisiology, Anatomy and Neuroscience, University of Szeged
NonREM sleep is characterized by intermittent periods of up and down states which appear in packets separated by microarousals and/or REM sleep episodes. Temporal progression of nonREM packets is characterized by an increase in the power of spindle oscillations in the cortex accompanied by a surge in the activity of low-firing pyramidal neurons, while high-firing pyramidal cells and fast-firing putative interneurons decrease their activity. However, the high-firing and fast-firing neurons might include several cell classes with unknown contribution to sleep packets. To reveal the firing dynamics of anatomically identified pyramidal cells (PCs), fast spiking interneurons (FSIs) and regular spiking interneurons (RSIs) during nonREM sleep, we applied juxtacellular recording and labelling of neurons in the parietal cortex during natural sleep in Wistar rats. Deep layer PCs and layer 3 PCs were more active compared to layer 2 PCs with sporadic firing encompassing nonREM packets. The firing of deep and superficial layer FSIs had the highest frequency which gradually increased as nonREM packets progressed and this was in correlation with an increasing power of spindle frequency band network oscillations. Cell to cell variability was found in the firing of RSIs with increasing, decreasing or stable firing rates during nonREM packets. Contribution to successive spindles during the timecourse of nonREM packets was cell class dependent, with only a subpopulation of FSIs with spindle trough related firing showing a change by increasing firing. Firing at the end of the delta waves started with a peak of FSI activity followed by RSIs and by PCs. The FSI-RSI-PC order of peak firing latencies remained stable during nonREM packets. In conclusion, cell class specific firing contribution might characterize nonREM sleep packets and ongoing spindle oscillations. Supported by: GINOP, HAS