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Fig. 5 | Acta Neuropathologica Communications

Fig. 5

From: Postnatal development and maturation of layer 1 in the lateral prefrontal cortex and its disruption in autism

Fig. 5

Layer 1 in the LPFC of the adult non-human primate (rhesus macaque). a Section labeled with Nissl showed a moderate density of neurons and glia, mainly astrocytes, in layer 1 (examples of neurons are marked with orange arrows, glial cells are marked with green arrows). Superficially, the glia limitans was visible as a dense band of astrocytes (shown with black arrows). b Myelin (Gallyas) stain showed the dense band of myelinated axons within superficial layer 1. Myelinated axons were seen penetrating layer 1 with diverse trajectories prior to joining the myelinated superficial plexus (black arrows). These axons came from long-range pathways or local interneurons. c Toluidine blue labeling of a 1 μm thick section from osmicated tissue revealed Nissl-stained cells and their processes, including profiles of myelinated axons (shown with black arrows). There was a higher density of thin axon profiles in superficial layer 1, in line with myelin stain shown in (b). Scale bar in inset measures 10 μm. d α-CamKII is a marker of synaptic turnover, and is used to identify areas of high plasticity. It labeled a dense population of processes in layer 1. e NeuN labels most neuronal nuclei, and in our material all layer 1 neurons that were labeled with Nissl were also labeled with NeuN (not shown). NeuN labeling clearly showed that the density of labeled neurons in layer 1 was low, and the majority of the cellular density in layer 1, as seen in (a), was not due to neurons but instead could be attributed to glia. f-g GABA (f) and GAD67 (g) label inhibitory neurons in the cortex (labeled with black arrows). There was a low density of labeling in both sections. Comparison with sections stained with NeuN (c) suggested that many neurons in layer 1 did not express GABA and its synthesizing enzymes strongly. h-j CB, CR, and PV labeled subpopulations of inhibitory interneurons. CB (h) and PV (j) did not label cell bodies in layer 1 in the adult non-human primate, while CR (i) labeled few cell bodies (shown with black arrows). PV (j) labeled a population of axons which joined the superficial plexus, and may represent either thalamocortical axons or axons of local inhibitory interneurons (shown with black arrows). CB (h) and CR (i) also labeled few axons in layer 1, but were not as visible as the PV-labeled processes. k Microglia with various morphologies, labeled with Iba-1, could be seen in layer 1. l GFAP labeled the cell bodies and dense processes of astrocytes within layer 1 (shown with green arrows). Images were acquired such that the top edge of the images underlie the pia. Dotted lines indicate the border with layer 2 in all panels. Calibration bar in (l) applies to all panels

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