Hippocampus lipid peroxidation induced by residual oil fly ash intranasal instillation versus habituation to the open field

Abstract

Epidemiological studies have demonstrated the adverse effects of particulate matter (PM) inhalation on the respiratory and cardiovascular systems. It has been reported that air pollution may affect the central nervous system and decrease cognitive function. In rats, residual oil fly ash (ROFA) instillation causes decreased motor activity and increased lipid peroxidation in the striatum and the cerebellum. Our objective was to determine whether chronic instillation of particles induces changes in learning and memory in rats and whether oxidants in the hippocampus may contribute to these adverse effects. Forty-five-day-old male Wistar rats were exposed to ROFA by intranasal instillation and were treated with N-acetylcysteine (NAC) at 150 mg/kg i.p. for 30 days. Control groups were exposed to ROFA, NAC, or neither. On days 1, 8, and 30 of the protocol, rats were submitted to the open field test to evaluate habituation. After the last open field session, the rats were killed by decapitation. The hippocampus was used to determine lipid peroxidation (LP) by the thiobarbituric acid-reactive substances test. ROFA instillation induced an increase in LP in the hippocampus compared to all treatment groups (p = .012). NAC treatment blocked these changes. All of the treatment groups presented a decrease in the frequency of peripheral walking (p = .001), rearing (p = .001), and exploration (p = .001) over time. Our study demonstrates that exposure to particles for 30 days and/or NAC treatment do not modify habituation to an open field, a simple form of learning and memory in rats, and that oxidative damage induced by ROFA does not modulate these processes.

Keywords::

• Habituation
• hippocampus
• lipid peroxidation
• particulate air pollution
• reactive oxygen species
• ROFA

Acknowledgments

Declaration of interest: This work was supported by Universidade Federal de Ciências da Saúde de Porto Alegre, Brazil. A.C. Zanchi is supported by a fellowship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—CAPES. Dr. C.R. Rhoden, Dr. H.M.T. Barros, and Dr. P.H.N. Saldiva are supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico—CNPq.