Depth-specific relationships between the molecular identity, intrinsic physiology and morphology of inhibitory interneurons in the rat neocortex

Felipe Yanez1, Daniel Udvary1, Fernando Messore1, Jason Guest1, Bert Sakmann2, Dirk Feldmeyer3, Marcel Oberlaender1

1 caesar Bonn
2 MPI of Neurobiology
3 Research Centre Juelich

We systematically assess the relationships between molecular, physiological and structural properties of inhibitory interneurons (INs) as a function of cortical depth in the rat barrel cortex. First, we determine the number and distribution of parvalbumin-, somatostatin- and VIP-expressing INs throughout the entire barrel cortex. The data provides quantitative estimates of the relative abundance of each of these molecularly defined IN classes across the cortical depth. Second, we objectively classify 290 in vitro recorded INs into physiological cell types based on their spiking patterns in response to somatic current injections. The neurons are recorded across the entire cortical depth of the barrel cortex. Third, based on somatic, dendritic and axonal reconstructions, we objectively classify the neurons into morphological cell types. For a subset of these neurons, we additionally determine their respective molecular identity. We compare the relative abundances across the cortical depth of molecularly defined IN classes, with those determined by morpho-electrical properties. Our results provide quantitative insight into the relationships between the three main attributes that are currently used to group INs, and reveal the degree to which somatic depth location in combination with molecular identity is predictive of an IN’s physiological and/or morphological cell type, and vice versa.