A comparative study of cortical distribution and density of calbindin inhibitory interneurons and neurons with calcium-binding proteins colocalization between mice and monkeys frontal and visual areas
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Abstract
The mouse is a widely used animal model in neuroscience, but the translational relationship from mice to primates is still under question. Previous studies have shown that between-area and between-species differences of pyramidal neurons exist between monkey and mouse frontal areas and V1 (Gilman et al., 2017). To provide more insights into this issue, we compared the laminar distribution and density of calcium-binding protein (CaBP) expressing inhibitory interneurons, which have different functions and properties. We specifically focused on calbindin (CB) interneurons and the colocalization of calbindin and with calretinin (CR) and parvalbumin (PV) in the same neuron, within monkey lateral prefrontal cortex (LPFC) and primary visual cortex (V1), and in functionally equivalent frontal and visual cortices in mouse (FC and V1). We stained coronal brain sections from each brain area and species by using the immunohistochemistry technique. The somata of CB+ interneurons were imaged across the entire cortical depth of each area using high-resolution confocal laser scanning microscopy and stereologically counted to quantify laminar distribution. Our data revealed a dense CB+ neuronal distribution in layers II/III in all monkey and mouse frontal and visual cortices; however, only monkey V1 showed a second peak in layer IV. When cortical depth was normalized, between-area differences in CB+ neuronal distribution were more pronounced in mouse compared to monkey frontal and visual cortices. The data also showed a higher density of CB+ neurons in superficial layers in the mouse compared to deep layers, but the density of CB+ neurons showed a similar pattern across superficial and deep layers in the monkey. In addition, there was a significantly higher density of CB+CR+ and CB+PV+ neurons in mouse compared to the monkey. Triple CB+CR+PV+ expressing neurons were rarely observed in monkey or mouse frontal and visual cortices. These findings contribute to understanding differences in inhibitory neuronal populations between rodents and primate brains.