DDT Exposure of Zebrafish Embryos Enhances Seizure Susceptibility: Relationship to Fetal p,p´-DDE Burden and Domoic Acid Exposure of California Sea Lions Jessica A. Tiedeken and John S. Ramsdell Marine Biotoxins Program, Center for Coastal Environmental Health and Biomolecular Research, National Oceanic and Atmospheric Administration—National Ocean Service, Charleston, South Carolina, USA Abstract Background: California sea lions have a large body burden of organochlorine pesticides, and over the last decade they have also been subject to domoic acid poisoning. Domoic acid poisoning, previously recognized in adult animals, is now viewed as a major cause of prenatal mortality. The appearance of a chronic juvenile domoic acid disease in the sea lions, characterized by behavioral abnormalities and epilepsy, is consistent with early life poisoning and may be potentiated by organochlorine burden. Objective: We investigated the interactive effect of DDT (dichlorodiphenyltrichloroethane) on neurodevelopment using a zebrafish (Danio rerio) model for seizure behavior to examine the susceptibility to domoic acid–induced seizures after completion of neurodevelopment. Methods: Embryos were exposed (6–30 hr postfertilization) to either o,p´-DDT or p,p´-DDE (dichlorodiphenyldichloroethylene) during neurodevelopment via a 0.1% dimethyl sulfoxide solution. These larval (7 days postfertilization) fish were then exposed to either the seizure-inducing drug pentylenetetrazol (PTZ) or domoic acid ; resulting seizure behavior was monitored and analyzed for changes using cameras and behavioral tracking software. Results: Embryonic exposure to DDTs enhanced PTZ seizures and caused distinct and increased seizure behaviors to domoic acid, most notably a type of head-shaking behavior. Conclusion: These studies demonstrate that embryonic exposure to DDTs leads to asymptomatic animals at completion of neurodevelopment with greater sensitivity to domoic acid–induced seizures. The body burden levels of p,p´-DDE are close to the range recently found in fetal California sea lions and suggest a potential interactive effect of p,p´-DDE embryonic poisoning and domoic acid toxicity. Key words: Danio rerio, DDT, domoic acid, seizures, zebrafish. Environ Health Perspect 117:68–73 (2009) . doi:10.1289/ehp.11685 available via http://dx.doi.org/ [Online 1 August 2008] Address correspondence to J.S. Ramsdell, Center for Coastal Environmental Health and Biomolecular Research, 219 Fort Johnson Rd., Charleston, SC 29412 USA. Telephone: (843) 762-8910. Fax: (843) 762-8700. E-mail: john.ramsdell@noaa.gov We thank J. Kucklick of the National Institute of Standards and Technology for use of his laboratory for gas chromatography/mass spectrometry analysis of organochlorines. This publication does not constitute an endorsement of any commercial product or intend to be an opinion beyond scientific or other results obtained by the National Oceanic and Atmospheric Administration (NOAA) . No reference shall be made to NOAA, or this publication furnished by NOAA, to any advertising or sales promotion which would indicate or imply that NOAA recommends or endorses any proprietary product mentioned herein, or which has as its purpose an interest to cause the advertised product to be used or purchased because of this publication. The authors declare they have no competing financial interests. Received 9 May 2008 ; accepted 1 August 2008. The full version of this article is available for free in HTML or PDF formats. |