Effect of congenital hypothyroidism on cell density in the ganglion cell layer of the rat retina

RESUMO

The effect of congenital hypothyroidism on the visual system of Wistar rats was studied by determining neuron density in the retinal ganglion cell layer. Retinae of adult rats from mothers treated with propylthiouracil, 50 mg/day, starting on the l5th day of pregnancy (PTU group), and of adult rats from untreated mothers (control group) were examined. Retinae were prepared, and the neurons in the nasotemporal region located above the optic disc were counted. Hypothyroid rats showed a significant reduction in the retinal area (about 6.8 per cent), when compared to controls. The cell density in the retinal ganglion cell layer was significantly decreased in 6 PTUtreated compared to 5 control retinae in total (2,793 ñ 330 vs 3,704 ñ 662 neurons/mm2), nasal (3,031 ñ 580 vs 3,853 ñ 699 neurons/mm2) and temporal (2,555 ñ 156 vs 3,555 ñ 827 neurons/mm2) regions. These alterations in a region considered to be one of the most specialized in the visual process suggest a structural deficiency induced by congenital hypothyroidism, with a possible decrease in the vísual acuity of the rat.