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Documenta Ophthalmologica

, Volume 110, Issue 1, pp 79–90 | Cite as

Repeated Spike Exposure to the Insecticide Chlorpyrifos Interferes with the Recovery of Visual Sensitivity in Rats*

  • Andrew M. Geller
  • Laura D. Sutton
  • Renée S. Marshall
  • Deborah L. Hunter
  • Victoria Madden
  • Robert L. Peiffer
Article

Abstract

Reports from Japan and India and data submissions to the US EPA indicate that exposure to cholinesterase (ChE)-inhibiting organophosphorous insecticides (OP) can produce ocular toxicity, in particular long-lasting changes in retinal physiology and anatomy. We have examined the effects of a 1 year dietary exposure to the OP chlorpyrifos (CPF) on retinal structure and function. Adult male Long-Evans rats were fed CPF in their diet at the rate of 0, 1 (low), or 5 (high) mg/kg body weight/day. In addition, half of each feeding group received an oral (spike) dose of CPF in corn oil (45 mg/kg) or corn oil (VEH) alone every 2 months, resulting in six exposure groups: Control-VEH, Control-CPF, Low-VEH, Low-CPF, High-VEH, and High-CPF. Dark-adapted electroretinograms (ERG) were measured 3–5 months (n=15–18/group) after the completion of dosing. There were no significant differences between dose or spike groups in a-wave, b-wave, or oscillatory potential amplitudes or implicit times. In addition, the time course of dark adaptation were measured in a subset of these rats (6–8/group) eight months after the completion of dosing by determining the flash intensity needed to elicit a 40 μV b-wave at selected intervals after bleaching 90% of the photopigment. Rats receiving the episodic oral spike of CPF showed a slowed recovery of dark-adapted sensitivity compared to rats receiving the corn oil VEH across chronic dosing conditions. No effects were seen on retinal morphology. This result suggests that episodic high dose exposures to CPF may result in altered retinal function. This effect, akin to effects seen in aging humans and humans exposed to other ChE-inhibiting compounds, may reflect alterations in the photoreceptors and retinal pigment epithelium (RPE) complex necessary for regenerating photopigment.

Keywords

chlorpyrifos dark adaptation electroretinogram ocular toxicity organophosphorous insecticide vision 

Abbreviations

ChE

cholinesterase

CPF

chlorpyrifos

CTL

control

ERG

electroretinogram

IP3

inositol 1,4,5-triphosphate

OP

organophosphorous pesticide

QNB

[3H]quinuclidinyl benzilate

TEM

transmission electron microscopy

VEH

corn-oil vehicle.

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Copyright information

© Springer 2005

Authors and Affiliations

  • Andrew M. Geller
    • 1
  • Laura D. Sutton
    • 1
  • Renée S. Marshall
    • 1
  • Deborah L. Hunter
    • 1
  • Victoria Madden
    • 2
  • Robert L. Peiffer
    • 3
  1. 1.Neurotoxicology Division, Office of Research and DevelopmentUS Environmental Protection AgencyResearch Triangle ParkUSA
  2. 2.Pathology and Laboratory MedicineUniversity of North Carolina at Chapel HillChapel HillUSA
  3. 3.Merck Research LaboratoriesWest PointUSA

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