Neurophysiological assessment of auditory, peripheral nerve, somatosensory, and visual system function after developmental exposure to gasoline, E15, and E85 vapors

David W Herr; Danielle L Freeborn; Laura Degn; Sheppard A Martin; Jayna Ortenzio; Lara Pantlin; Charles W Hamm; William K Boyes

doi:10.1016/j.ntt.2015.12.006

Neurophysiological assessment of auditory, peripheral nerve, somatosensory, and visual system function after developmental exposure to gasoline, E15, and E85 vapors

Neurotoxicol Teratol. 2016 Mar-Apr:54:78-88. doi: 10.1016/j.ntt.2015.12.006. Epub 2015 Dec 22.

Authors

David W Herr¹, Danielle L Freeborn², Laura Degn³, Sheppard A Martin⁴, Jayna Ortenzio⁵, Lara Pantlin⁶, Charles W Hamm⁷, William K Boyes⁸

Affiliations

¹ Neurotoxicology Branch, Toxicity Assessment Division, MD B105-04, NHEERL, ORD, U.S. E.P.A., Research Triangle Park, NC 27711, USA. Electronic address: Herr.david@epa.gov.
² Neurotoxicology Branch, Toxicity Assessment Division, MD B105-04, NHEERL, ORD, U.S. E.P.A., Research Triangle Park, NC 27711, USA. Electronic address: Freeborn.danielle@epa.gov.
³ Neurotoxicology Branch, Toxicity Assessment Division, MD B105-04, NHEERL, ORD, U.S. E.P.A., Research Triangle Park, NC 27711, USA. Electronic address: Degn.laura@epa.gov.
⁴ Neurotoxicology Branch, Toxicity Assessment Division, MD B105-04, NHEERL, ORD, U.S. E.P.A., Research Triangle Park, NC 27711, USA. Electronic address: sam506@gmail.com.
⁵ Student Contractor to the U.S. E.P.A. Research Triangle Park, NC 27711, USA. Electronic address: Ortenzio.jayna@epa.gov.
⁶ Meredith College, Raleigh, NC 27607, USA. Electronic address: lpantlin@rams.colostate.edu.
⁷ Neurotoxicology Branch, Toxicity Assessment Division, MD B105-04, NHEERL, ORD, U.S. E.P.A., Research Triangle Park, NC 27711, USA. Electronic address: Hamm.charlesw@epa.gov.
⁸ Neurotoxicology Branch, Toxicity Assessment Division, MD B105-04, NHEERL, ORD, U.S. E.P.A., Research Triangle Park, NC 27711, USA. Electronic address: Boyes.william@epa.gov.

PMID: 26721698
DOI: 10.1016/j.ntt.2015.12.006

Abstract

The use of gasolines blended with a range of ethanol concentrations may result in inhalation of vapors containing a variable combination of ethanol with other volatile gasoline constituents. The possibility of exposure and potential interactions between vapor constituents suggests the need to evaluate the possible risks of this complex mixture. Previously we evaluated the effects of developmental exposure to ethanol vapors on neurophysiological measures of sensory function as a component of a larger project evaluating developmental ethanol toxicity. Here we report an evaluation using the same battery of sensory function testing in offspring of pregnant dams exposed during gestation to condensed vapors of gasoline (E0), gasoline blended with 15% ethanol (E15) or gasoline blended with 85% ethanol (E85). Pregnant Long-Evans rats were exposed to target concentrations 0, 3000, 6000, or 9000 ppm total hydrocarbon vapors for 6.5h/day over GD9 - GD20. Sensory evaluations of male offspring began as adults. The electrophysiological testing battery included tests of: peripheral nerve (compound action potentials, nerve conduction velocity [NCV]), somatosensory (cortical and cerebellar evoked potentials), auditory (brainstem auditory evoked responses), and visual functions. Visual function assessment included pattern elicited visual evoked potentials (VEP), VEP contrast sensitivity, dark-adapted (scotopic) electroretinograms (ERGs), light-adapted (photopic) ERGs, and green flicker ERGs. The results included sporadic statistically significant effects, but the observations were not consistently concentration-related and appeared to be statistical Type 1 errors related to multiple dependent measures evaluated. The exposure concentrations were much higher than can be reasonably expected from typical exposures to the general population during refueling or other common exposure situations. Overall the results indicate that gestational exposure of male rats to ethanol/gasoline vapor combinations did not cause detectable changes in peripheral nerve, somatosensory, auditory, or visual function when the offspring were assessed as adults.

Keywords: E15 vapor, E85 vapor, developmental neurotoxicity; Electroretinogram; Gasoline vapor; Nerve conduction velocity; Sensory evoked potentials.

Published by Elsevier Inc.

MeSH terms

Acoustic Stimulation
Action Potentials / drug effects
Administration, Inhalation
Air Pollutants / toxicity*
Analysis of Variance
Animals
Dose-Response Relationship, Drug
Electroretinography
Evoked Potentials / drug effects*
Female
Gasoline / toxicity*
Male
Neural Conduction / drug effects
Neural Conduction / physiology
Peripheral Nerves / drug effects*
Peripheral Nerves / physiology
Photic Stimulation
Pregnancy
Prenatal Exposure Delayed Effects / chemically induced
Prenatal Exposure Delayed Effects / physiopathology*
Rats
Rats, Long-Evans

Substances

Air Pollutants
Gasoline