Influence of visual experience deprivation on the postnatal development of the microvascular bed in layer IV of the rat visual cortex

Cerebral vascular density is correlated with metabolic demands, which increase in highly active brain areas. External inputs are an essential requirement in the modeling of the visual cortex. Experience-mediated development is very active during the first postnatal month, when congruous blood supply is needed. We studied the development of visual cortex vascularization in relation to experience, comparing rats raised in darkness with rats reared in normal conditions. Vascular density, vascular area and their ratio vs. neuronal density were calculated. Conventionally stained semi-thin sections were used to measure the vascular area by computer assisted morphometry. Animals from both groups were sampled at 14, 21, and 60 days postnatal (dpn). We found a significantly lower density of vessels and neurons as well as a smaller vascular area in dark-reared adult rats while no differences were founded at the other ages. Our results also show no differences between the ratio of vessels/neuron, and vascular area/neuron, between both groups. The absence of visual experience causes decrease of cortical activity which correlates with lower vessels density and vascular area, without their ratio/neuron being affected.