Effect of Inhalation of Formaldehyde on the Structure of Hippocampus of Albino Rat and the Possible Protective Role of Omega-3

Abstract

ABSTRACTBackground: Formaldehyde (FA) is a vastly used chemical structure with which every physician had a first-hand experience in his early days of training in the anatomy laboratory. The National Institute of Occupational Safety and Health listed 52 occupations that expose people to FA. Omega-3 polyunsaturated fatty acids (PUFAs) are important for brain development and performance especially in the hippocampus. They improve spatial and long term memory and learning functions, enhance synaptogenesis and boost hippocampal neurite development.Aim of work: To investigate the effect of exposure to FA vapor on the structure of hippocampus and to study the possible protective role of Omega-3.Material and Methods: Rats were divided into three groups; each group was composed of eight rats. Group I: used as control. Group II: rats were exposed to 10% FA for 6 hours/ day, every other day for 6 weeks. Group III: rats were exposed to 10% FA for 6 hours/ day, every other day for 6 weeks; simultaneously Omega-3 was given orally as 300 mg/kg body weight daily throughout the 6 weeks. At the end of the experiment, the rats were anaesthetized, brains dissected and specimens were processed for light microscopy.Results: Histological study indicated that in FA exposed group, some regions of cornu Ammonis (CA) showed pyramidal cells with large rarefied lightly stained nuclei while other regions showed degenerated pyramidal cells. Pyknotic small deeply stained nuclei were also noticed. Oligodendrocytes were seen in close relation to some of the degenerated cells. Neuronal processes were broken, replaced by vacuolated swollen elongated spaces. Ramifying processes of the astrocytes were extensively seen extending in-between the pyramidal cells and also in the molecular and polymorphic layers as well. Occasional apoptotic cells were seen. In Omega treated group, pyramidal cells appeared large triangular with large vesicular nuclei and prominent nucleoli. However, few pyramidal cells showed vacuolation and degeneration of the cytoplasm, their nuclei were deeply stained and were either irregular or shrunken small pyknotic. Few oligodendrocytes were seen encroaching and settling close to some pyramidal cells. Some apical dendrites preserved their integrity being directed towards the molecular layer. In addition, no apoptotic cells could be detected. In statistical results, in group exposed to FA, there was a significant decrease in pyramidal cell count compared to control group and non-significant decrease compared to Omega group. Also, there was a significant decrease in pyramidal layer thickness compared to control and Omega groups.Conclusion: FA exposure may have serious effects on human hippocampal structure, if exposure to formaldehyde is inevitable, it is advised to use a protective antioxidant such as Omega-3 simultaneously which may diminish the hazardous effect of FA on the hippocampal structure and function.