Synaptic properties of layer VI inverted pyramidal cells in the rodent somatosensory cortex.

The properties of specific cortical cell types enable greater understanding of how cortical microcircuits process and transmit sensory, motor, and cognitive information. Previous reports have characterized the intrinsic properties of the inverted pyramidal cell (IPC) where the most prominent dendrite is orientated towards the cortical white matter. Using whole cell patch clamp recordings from rat and mouse somatosensory cortex in conjunction with electric microstimulation of the white matter we characterized the synaptic inputs onto IPCs and the more common upright pyramidal cell (UPC) in the infragranular layers. Both classes of pyramidal cells received monosynaptic glutamatergic input following white matter stimulation, but varied on a number of parameters. Most prominently, UPCs displayed higher amplitude responses and showed greater rates of depression compared to IPCs. These data reinforce the view that IPCs are a separate functional class of cortical neuron.