Comparisons of calretinin and parvalbumin neuronal distribution, density and inhibitory synapses in rhesus monkey prefrontal cortex and primary visual cortex and the analogous areas of mice
Nasar, Rakin Tammam
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Calretinin (CR) and parvalbumin (PV) neurons are inhibitory interneurons (INs) that play important roles in the modulation of excitatory pyramidal neurons. They are found in many species are and throughout the neocortex. However, their characteristics vary between species and brain region. The aim of this study was to compare the density, distribution, and inhibitory signaling of CR and PV neurons in monkey primary visual cortex (V1), monkey lateral prefrontal cortex (LPFC), mouse V1 and mouse frontal cortex (FC). Coronal brain slices from each of the species and brain regions were stained using immunohistochemistry and then the slices were scanned using high-resolution confocal imaging. High resolution image stacks were used to count the somata of CR and PV. The vesicular gamma aminobutyric acid (GABA) transporter (VGAT), CR and PV particles were analyzed to quantify these inhibitory markers in monkey V1, LPFC, and mouse V1 and FC. There were significant differences in the laminar distribution of CR and PV neurons in that CR neurons were concentrated in L2/3 and PV neurons were concentrated in L2-5. In L2/3, Monkey V1 had more CR neurons than did monkey LPFC. Furthermore, there were a greater number of PV neurons in monkey and mouse V1 compared to monkey LPFC and mouse FC. In L2/3, monkey V1 had the highest number of PV neurons. In L5, there significantly greater PV neurons in mouse V1 compared to monkey V1. There was significantly higher density of CR neurons in the upper middle layers of Monkey V1 compared to mouse V1 and monkey LPFC compared to mouse FC. The upper middle layers of monkey V1 had significantly higher density of PV neurons compared to monkey LPFC and mouse V1. There was significantly higher density of VGAT particles in monkey V1 and LPFC compared to mouse V1 and FC, which indicates more inhibitory synapses. There were significantly more VGAT+ boutons colocalized with PV+ boutons than CR+ boutons. Finally, discriminant analysis and hierarchical cluster analysis show that species is the largest separating factor between monkey V1, LPFC and mouse V1 and FC. Mouse V1 and FC are very similar, and monkey V1 and LPFC are dissimilar from one another. This data, united with comparative data on pyramidal neurons, demonstrates that neurons have differences between species, and monkeys have more regional specialization than mice.
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