Central nervous system toxicity after acute oral formaldehyde exposure in rabbits: An experimental study

Formaldehyde (FA) is one of the most widely used chemical compounds in industrial field. It is described as toxic, particularly to the nervous system, the urogenital system, and the respiratory tracts. In this study, we determined the effects of acute oral exposure to FA in rabbit brain tissue. A total of 16 rabbits were selected and divided into 2 groups: formaldehyde group (group F) and control group (group C). FA was administered to group F at a rate of 40 mg/kg/day via a nasogastric tube for 5 days. Saline was similarly administered to the eight controls. All the animals were euthanized after 5 days of exposure, and brain tissue samples were collected in 10% neutral formalin and embedded in paraffin. To investigate the effects of FA on the apoptotic process, we examined active caspase-3, Bax, and Bcl-2 immunohistochemical expression and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate -biotin nick-end labeling (TUNEL) reactivity in the rabbit brains. In addition, glial fibrillary acidic protein (GFAP) was biochemically assessed in brain tissue samples for neurotoxicity. We found that FA treatment caused a significant decrease in Bcl-2 expression and an increase in active caspase-3 and Bax expressions as well as an increase in the number of TUNEL-positive apoptotic cells. The GFAP level was found to be significantly higher in group F. In conclusion, acute oral exposure to FA caused DNA damage, apoptosis, and neuronal injury in the rabbit brains.