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Effects of Fipronil on the EEG of Long Evans Rats
Citation:
LYKE, D. F., K. MCDANIEL, V. C. MOSER, AND D. W. HERR. Effects of Fipronil on the EEG of Long Evans Rats. Presented at Society of Toxicology (SOT) Annual Meeting, Washington, DC, March 06 - 10, 2011.
Impact/Purpose:
In the current study, we examined the ability to detect changes in EEG activity produced by fipronil, a phenylpyrazole pesticide that inhibits GABA receptors
Description:
We have reported that the non-stimulus driven EEG is differentially altered by deltamethrin or permethrin (Lyke and Herr, Toxicologist, 114(S-1):265, 2010). In the current study, we examined the ability to detect changes in EEG activity produced by fipronil, a phenylpyrazole pesticide that inhibits GABA receptors. Adult male Long-Evans rats were dosed with fipronil (po). Rangefinding studies (40 or 50 mg/kg, n=5/dose) were conducted using observations of neurological signs, and grip strength and landing foot splay. The data suggested increased handling reactivity, mild tremors and gait changes, circling, decreased hindlimb grip strength, and increased foot splay. Maximal effects were evident about 5 to 8 hours after dosing. Additional rats were implanted with epidural screw electrodes. After about 1 week recovery, non-restrained animals were gavaged with com oil and tested for 2 days to allow acclimation. On day 3, the rats were dosed with 1 ml/kg vehicle (com oil), 25 mg/kg fipronil, or 50 mg/kg fipronil and tested 6 h later. EEG was recorded as 30 segments of 2 s durations, transformed using a FFT, and the spectra averaged. Treatment with 25 and 50 mg/kg fipronil decreased the area (17-25% decrease) associated with Gamma activity when recorded between the visual cortex and frontal cortex. The peak amplitude of this Gamma activity was decreased (20% decrease) by 50 mg/kg fipronil. These results differ from the previously reported increases in Gamma activity following treatment with permethrin (11-25% increase in amplitude-area), and lack of changes after dosing with deltamethrin. The data show that fipronil can alter CNS activity as measured by EEG, and the alterations may differ from some other pesticides. This is an abstract ofa proposed presentation and does not necessarily reflect EPA policy.