Cell type-specific subcortical targets of layer 5 projecting neurons in the rat vibrissal cortex

Layer 5 pyramidal neurons provide the mayor output of the cortex and consequently likely to be important modulators of sensory and motor processes. This subcortical layer 5 projecting neurons are morphologically and physiologically heterogeneous and project to distinct intracortical and subcortical targets. However, since most of physiological and morphological studies of layer 5 pyramidal neurons have been carried out in unidentified cells, little is known about morphological characteristics related to subcortical projection site. This is important to understand the specificity at single cell level between structural and functional properties in vivo in the mammalian brain. Here, we use retrograde neuronal tracing to analyze the distribution of different populations of subcortical projecting neurons in the rat barrel field somatosensory cortex (BFSI). Additionally, we combine retrograde neuronal tracing with whole cell and juxtacellular recordings in order to fill and reconstruct 3D patterns of functional identified neurons and distinguish special morphological characteristics of each cell type. In this way, we provide unprecedented insight into cell type-specific structural and sensory-evoked functional properties of long-range projection neurons in layer 5 of rat vibrissal cortex