Effects of diazinon on olfactory epithelium and genes related to olfactory signal transduction in Caspian roach, Rutilus caspicus

Olfaction in fishes is biologically-essential chemoreceptors. It provokes important behaviors for the survival of fish such as feeding, reproduction, avoiding predator and intraspecific communication. Pesticides can affect the olfactory epithelium and genes related to olfactory transduction and impair olfactory function.  The present study aims to determine how toxicity of diazinon impacts olfaction of Caspian roach, Rutilus caspicus in histological and gene levels. We exposed fish (0.7 ± 0.05 g in weight) to 0, 1, 2 and 3 mg L-1 diazinon (60 fish in each 3- replicate 60-L glass tank) for 7 days in freshwater. Diazinon concentrations were chosen based on reports on its concentration in surface waters. Mortality rate, histological events of olfactory epithelium, and genes expression at the 7th day after diazinon exposure included a significant decrease in the number of olfactory receptor cells (ORCs), while increased goblet cells (GCs). In addition, G protein αi (Gpαi) was significantly upregulated, whereas calmodulin-dependent kinase II α (CaMKIIα) was significantly downregulated after 7 days as compared to the control group. These results indicate that diazinon can impair olfactory function through effect on the olfactory epithelium and olfactory signal transduction pathways in the Caspian roach fingerlings.