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| Research article summary (published 30 Mar 2009): |
Gestational methylmercury exposure selectively increases the sensitivity of operant behavior to cocaine.
Full Abstract
Developmental methylmercury (MeHg) exposure alters dopamine neurotransmitter systems, but the selectivity of this and the effects of low, environmentally relevant MeHg exposure regimens are poorly understood. In previous reports, some including littermates of animals studied here, chronic, low-level exposures affected performance on reversal tasks and enhanced reinforcer efficacy. Using high- and low-rate operant behavior under a fixed interval (FI) schedule, sensitivity was examined to drugs that target noradrenergic and dopaminergic neurotransmitter systems. Female rats were exposed in utero to 0, 0.5, or 5 ppm of mercury, as MeHg, via maternal drinking water. Selenium (Se) is thought to attenuate MeHg's neurotoxicity, so animals consumed a diet containing 0.06 or 0.6 ppm of Se. At 11 months, they lever-pressed under a FI 120" schedule of sucrose reinforcement. Acute dose-effect curves were generated with cocaine, desipramine, SKF-38393, quinpirole, SCH-23390, and sulpiride. As compared with unexposed animals, those exposed to 5 ppm mercury, regardless of Se exposure, were 2 to 3 times more sensitive to the rate-reducing effects of high doses of cocaine and did not show increased responding earlier in the interval following moderate cocaine doses. Cocaine's effects in the 0.5 ppm Hg groups depended on dietary Se: low Se diet resulted in a rightward shift in the DEC compared to controls, whereas a high Se diet did not. No differential effects of MeHg were seen with the other drugs. Gestational MeHg exposure produces irreversible sensitivity to dopamine, but not norepinephrine, reuptake inhibitors and not to drugs that target D1 or D2 receptors. (c) 2009 APA, all rights reserved.
Author information
Author/s: Reed, Miranda N (MN); Newland, M Christopher (MC);
Affiliation: Department of Psychology, Auburn University, Auburn, Alabama 36830, USA.
Grants: ES 10865 (Agency:NIEHS NIH HHS)
Journal and publication information
Publication Type: Journal Article; Research Support, N.I.H., Extramural
Journal: Behavioral neuroscience (Behav Neurosci), published in United States. (Language: eng)
Reference: 2009-Apr; vol 123 (issue 2) : pp 408-17
Dates: Created 2009/03/31; Completed 2009/05/18;
PMID: 19331463, status: MEDLINE (last retrieval date: 5/18/2009, IMS Date: 18 May 2009 00:00:00)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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