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Acute Inhalation of 2,2,4-Trimethylpentane Alters Visual Evoked Potentials and Signal Detection Behavior in Rats
Citation:
BOYES, W. K., W. M. OSHIRO, H. A. EL-MASRI, L. DEGN, M. S. BERCEGEAY, Q. T. KRANTZ, AND P. J. BUSHNELL. Acute Inhalation of 2,2,4-Trimethylpentane Alters Visual Evoked Potentials and Signal Detection Behavior in Rats. NEUROTOXICOLOGY AND TERATOLOGY. Elsevier Science Ltd, New York, NY, 32(5):525-535, (2010).
Impact/Purpose:
The potential neurological impairment from acute inhalation exposure to TMP was evaluated in adult male Long-Evans rats using both electrophysiological and behavioral assessments.
Description:
The volatile organic compound 2,2,4-trimethylpentane (TMP, "isooctane") is a constituent of gasoline for which the current health effects data are insufficient to permit the US Environmental Protection Agency to conduct a risk assessment. The potential neurological impairment from acute inhalation exposure to TMP was evaluated in adult male Long-Evans rats using both electrophysiological and behavioral assessments. Visual evoked potentials (VEPs) were recorded from rats viewing modulated visual patterns (0.16 cycles per degree visual angle (cpd), 60% contrast, 4.55 Hz appear/disappear). Rats (n=7-10/dose) were exposed to TMP vapors in concentrations of 0, 500, or 1000 ppm for 60-min. A VEP was recorded before exposure and at 10 min intervals during exposure and also for 60 min after exposure terminated. The spectral amplitude of the frequency-double component (F2) was significantly reduced by exposure to 500 or 1000 ppm TMP. In behavioral assessments, rats (n=14) performed an appetitively motivated visual signal detection task while breathing 0, 500, 1500, 1000, 2000, or 2500 ppm TMP for 62 min. Slight reductions in accuracy of performance were observed in the 2000 and 2500 ppm concentrations. Concentrations of TMP in the brain were estimated by a physiologically based pharmacokinetic (PBPK) model to be less than 0.2 mM after 62 min at 2500 ppm. Together these data demonstrate that TMP, like other volatile organic substances, impairs neurological function during acute inhalation exposure and that the small magnitude of the observed effects is consistent with the low concentrations of this hydrocarbon that reach the CNS. Key
