Age-Related Structural Changes in Primary Visual Cortex Cells of Rats under High-Intensity Light Exposure

Abstract

An experiment using 20 white male Wistar rats has shown that exposure to 3500 lux of light for 7 days causes morphological changes in the II, IV, and V layers of the primary visual cortex. This was seen in an increased percentage of reversibly and irreversibly altered neurons, mainly in the fourth layer of 18-month-old rats (p ≤ 0.05). In response to light exposure, the percentage of hyperchromic wrinkled neurons in 18‑month-old rats rises to 6% (5; 8.5), the percentage of neurons with total chromatolysis rises to 10% (8.5; 14) compared to a 1% (0.5; 14) and 6% (5; 8) rise in 3-month-old rats respectively (p ≤ 0.05). The neural damage leads to a glial reaction reflected in an increased percentage of glia with signs of edema and swelling, hyperchromia without the nucleus and cytoplasm shrinkage (p ≤ 0.05), neuronophagia, and also the intrusion of the glia cells into the neuron cytoplasm for the initiation of intracellular reparation. The destructive changes are characterized by the gliacyte hyperchromia with the shrinkage of the nucleus and cytoplasm. The percentage of these gliacytes increases significantly in 18-month-old rats under the light exposure compared to the indices in young animals (p ≤ 0.05).