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Comparative developmental neurotoxicity of organophosphate insecticides: effects on brain development are separable from systemic toxicity.

Publication ,  Journal Article
Slotkin, TA; Levin, ED; Seidler, FJ
Published in: Environ Health Perspect
May 2006

A comparative approach to the differences between systemic toxicity and developmental neurotoxicity of organophosphates is critical to determine the degree to which multiple mechanisms of toxicity carry across different members of this class of insecticides. We contrasted neuritic outgrowth and cholinergic synaptic development in neonatal rats given different organophosphates (chlorpyrifos, diazinon, parathion) at doses spanning the threshold for impaired growth and viability. Animals were treated daily on postnatal days 1-4 by subcutaneous injection so as to bypass differences in first-pass activation to the oxon or catabolism to inactive products. Evaluations occurred on day 5. Parathion (maximum tolerated dose, 0.1 mg/kg) was far more systemically toxic than was chlorpyrifos or diazinon (maximum tolerated dose, 1-5 mg/kg). Below the maximum tolerated dose, diazinon impaired neuritic outgrowth in the forebrain and brainstem, evidenced by a deficit in the ratio of membrane protein to total protein. Diazinon also decreased choline acetyltransferase activity, a cholinergic neuronal marker, whereas it did not affect hemicholinium-3 binding to the presynaptic choline transporter, an index of cholinergic neuronal activity. There was no m(subscript)2(/subscript)-muscarinic acetylcholine receptor down-regulation, as would have occurred with chronic cholinergic hyperstimulation. The same pattern was found previously for chlorpyrifos. In contrast, parathion did not elicit any of these changes at its maximum tolerated dose. These results indicate a complete dichotomy between the systemic toxicity of organophosphates and their propensity to elicit developmental neurotoxicity. For parathion, the threshold for lethality lies below that necessary for adverse effects on brain development, whereas the opposite is true for chlorpyrifos and diazinon.

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Published In

Environ Health Perspect

DOI

ISSN

0091-6765

Publication Date

May 2006

Volume

114

Issue

5

Start / End Page

746 / 751

Location

United States

Related Subject Headings

  • Toxicology
  • Rats, Sprague-Dawley
  • Rats
  • Pregnancy
  • Organophosphorus Compounds
  • Insecticides
  • Female
  • Brain
  • Animals
  • 42 Health sciences
 

Citation

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Slotkin, T. A., Levin, E. D., & Seidler, F. J. (2006). Comparative developmental neurotoxicity of organophosphate insecticides: effects on brain development are separable from systemic toxicity. Environ Health Perspect, 114(5), 746–751. https://doi.org/10.1289/ehp.8828
Slotkin, Theodore A., Edward D. Levin, and Frederic J. Seidler. “Comparative developmental neurotoxicity of organophosphate insecticides: effects on brain development are separable from systemic toxicity.Environ Health Perspect 114, no. 5 (May 2006): 746–51. https://doi.org/10.1289/ehp.8828.
Slotkin, Theodore A., et al. “Comparative developmental neurotoxicity of organophosphate insecticides: effects on brain development are separable from systemic toxicity.Environ Health Perspect, vol. 114, no. 5, May 2006, pp. 746–51. Pubmed, doi:10.1289/ehp.8828.

Published In

Environ Health Perspect

DOI

ISSN

0091-6765

Publication Date

May 2006

Volume

114

Issue

5

Start / End Page

746 / 751

Location

United States

Related Subject Headings

  • Toxicology
  • Rats, Sprague-Dawley
  • Rats
  • Pregnancy
  • Organophosphorus Compounds
  • Insecticides
  • Female
  • Brain
  • Animals
  • 42 Health sciences