Organophosphate insecticides target the serotonergic system in developing rat brain regions: disparate effects of diazinon and parathion at doses spanning the threshold for cholinesterase inhibition.

Published

Journal Article

BACKGROUND: In the developing brain, serotonin (5HT) systems are among the most sensitive to disruption by organophosphates. OBJECTIVES: We exposed neonatal rats to daily doses of diazinon or parathion on postnatal days (PND)1-4 and evaluated 5HT receptors and the 5HT transporter in brainstem and forebrain on PND5, focusing on doses of each agent below the maximum tolerated dose and spanning the threshold for cholinesterase inhibition: 0.5, 1, or 2 mg/kg for diazinon, and 0.02, 0.05, and 0.1 mg/kg for parathion. RESULTS: Diazinon evoked up-regulation of 5HT1A and 5HT2 receptor expression even at doses devoid of effects on cholinesterase activity, a pattern similar to that seen earlier for another organophosphate, chlorpyrifos. In contrast, parathion decreased 5HT1A receptors, again at doses below those required for effects on cholinesterase. The two agents also differed in their effects on the 5HT transporter. Diazinon evoked a decrease in the brainstem and an increase in the forebrain, again similar to that seen for chlorpyrifos; this pattern is typical of damage of nerve terminals and reactive sprouting. Parathion had smaller, nonsignificant effects. CONCLUSIONS: Our results buttress the idea that, in the developing brain, the various organophosphates target specific neurotransmitter systems differently from each other and without the requirement for cholinesterase inhibition, their supposed common mechanism of action.

Full Text

Duke Authors

Cited Authors

  • Slotkin, TA; Tate, CA; Ryde, IT; Levin, ED; Seidler, FJ

Published Date

  • October 2006

Published In

Volume / Issue

  • 114 / 10

Start / End Page

  • 1542 - 1546

PubMed ID

  • 17035140

Pubmed Central ID

  • 17035140

International Standard Serial Number (ISSN)

  • 0091-6765

Digital Object Identifier (DOI)

  • 10.1289/ehp.9337

Language

  • eng

Conference Location

  • United States