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Bjorn Ekesten, Kristy Brown, Peter Gouras; Types of Cell Bodies found in Layer 1 of Murine Striate Cortex. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4997.
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© ARVO (1962-2015); The Authors (2016-present)
To examine the neural circuitry of layer 1 of murine visual cortex starting by describing the variety of cell bodies present in this relatively acellular layer. In particular we are looking for inter-neurons detected in layer 1 by physiological methods (Chu Z & al.,J. Neurosci. 2003, 23(1):96-102).
Mice were deeply anesthetized and perfused through the ascending aorta with 4% glutaraldehyde in phosphate buffered saline. Small segments of striate cortex were cut out extending radially toward the more inner cortical layers. We use serial sectioning electron microscopy and digital image processing to classify cell types using their unique morphology as criteria.
Layer 1 is an extensive neuropile filled mainly by myelinated axons and dendrites, the latter from pyramidal neurons located in deeper layers. Axo-dendritic synapses are observed between these structures. There is a tendency for ascending dendrites to form local bouquets without overlap with neighboring dendritic bouquets. We have found 3 varieties of cell bodies in layer 1: astrocytes (56%), oligodendrocytes (32%) and microglia (12%). We have not counted endothelium, pericytes, and epithelial border cells. We have not yet found neuronal cell bodies in the upper strata of layer 1.
Layer 1 is an extensive neuropile with large dendrites of pyramidal cells whose cell bodies reside in deeper cortical layers. The dendritic arbors extend vertically and do not ramify with the dendrites of neighboring pyramidal cells, suggesting a columnar organization. Synapses are found between incoming axons and these dendrites. All of the cell bodies we have detected so far in layer 1 are glial including astrocytes, oligodendrocytes and microglia. Inter-neurons must be relatively rare or perhaps situated deeper in layer 1.
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