LAMINAR SPECIFICITY OF PERISOMATIC INHIBITION IN THE MOUSE PREFRONTAL CORTEX
Petra Nagy-Pál1, Judit M. Veres1, Rita M. Karlócai1, Zsuzsanna Fekete1, Filippo Weisz and Norbert Hájos1
Perisomatic inhibition provided by local GABAergic interneurons is critical for cortical functions, but the details of these inhibitory circuits, especially in associative cortices, are still unknown. Here, we examined the laminar specificity of two types of basket cells (BC) expressing parvalbumin (PV) or cholecystokinin (CCK) in the mouse prefrontal cortex (PFC). Using whole-cell patch clamp technique, we performed recordings in acute slices containing the PFC. The recordings were accompanied by intracellular labeling that allowed us to identify the interneuron types post hoc. We observed that BCs located in distinct layers differed in their morphological features. Examining the distribution of axons and dendrites of PVBCs, we found layer preferences in both types of processes. In contrast, CCKBCs displayed layer-specific differences only in their dendritic arborization. In addition, we examined the inputs from extra-PFC afferents onto PV-expressing interneurons using trans-synaptic viral approach. We observed that afferents from the thalamus and basal amygdala preferentially innervate PV-expressing cells in the layer 5a and 5b, respectively. Moreover, using retrograde tracing and single cell labeling, we examined the innervation of pyramidal cells by PVBCs. The analyses uncovered that single PVBCs contacted pyramidal cells with distinct projections. These results suggest that morphologically different BCs are present in the PFC microcircuits. Furthermore, PVBCs in different layers are preferentially contacted by distinct extra-PFC afferents and innervate pyramidal cells in their vicinity irrespective where they project. Thus, BCs innervating all pyramidal cells in their neighborhood may control PFC function in a layer-specific manner.