65 January 2023. Volume 17. Number 1 Ava Resae , *Mohammad Hasan Yousefi , Saeideh Naeimi, Ali Mahdavi Department of Basic Sciences, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran. * Corresponding Author: Mohammad Hasan Yousefi Address: Department of Basic Sciences, Faculty of Veterinary Medicine, Semnan University, Semnan, Iran. Phone: +98 (23) 33654215 E-mail: myousefi@semnan.ac.ir Original Article Effects of Occupational Formaldehyde Exposure on Passive Avoidance Conditioning and Anxiety Levels in Wistar Rats Background: Formaldehyde is a volatile organic compound widely used in industry and medical felds such as Anatomy and Pathology. Exposure to this chemical negatively affects the skin, mucous membrane, and respiratory system. It can pass through the blood-brain barrier, potentially causing neurotoxicity. According to studies, formaldehyde might be involved in memory impairment and the cognitive decline process in Alzheimer disease (AD). Objectives: This study aimed to simulate chronic occupational formaldehyde exposure in rats and study its impacts on passive avoidance conditioning and anxiety. Methods: Twenty-four adult male Wistar rats were divided into four groups of 6 rats each. After an adaptation period, the rats were exposed to 1, 2, and 3 ppm formaldehyde vapor in an exposure chamber, 6 hours per day for 7 days. The control group was exposed to saline. After the exposure period, a shuttle box for passive avoidance conditioning and an elevated plus-maze test for assessing anxiety levels were performed. The data were analyzed by 1-way ANOVA and Duncan’s multiple range test for group comparison in SPSS and SAS software. Results: In the shuttle box test, formaldehyde dose-dependently decreased escape- through latency and increased the percentage of dark compartment entries (P<0.0001). In the elevated plus maze test, the percentage of time spent in open arms decreased by increasing the dosage (P<0.0001). Conclusion: Based on these fndings, formaldehyde exposure can negatively alter brain function and cause memory impairment and anxiety. Keywords: Anxiety, Formaldehyde, Memory, Rat, Shuttle box A B S T R A C T How to Site This Article Resae, A., Yousefi, M. H., Naeimi, S., and Mahdavi, A. (2023). Effects of Occupa- tional Formaldehyde Exposure on Passive Avoidance Conditioning and Anxiety Levels in Wistar Rats. Iranian Journal of Veterinary Medicine, 17(1): 65-74. http://dx.doi.org/10.32598/ijvm.17.1.1005241 http://dx.doi.org/10.32598/ijvm.17.1.1005241 Use your device to scan and read the article online Article info: Received: 07 Jun 2022 Accepted: 22 Aug 2022 Publish: 01 Jan 2023