Response inhibition is impaired by developmental methylmercury exposure: Acquisition of low-rate lever-pressing
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- 作者：M. Christopher Newl ; Daniel J. Hoffman ; John C. Heath ; Wendy D. Donlin
- 关键词：Response inhibition ; Reversal learning ; Percentile Schedule ; Methylmercury ; Selenium ; Developmental neurotoxicology
- 刊名：Behavioural Brain Research
- 出版年：2013
- 出版时间：15 September, 2013
- 年：2013
- 卷：253
- 期：Complete
- 页码：196-205
- 全文大小：1300 K
文摘
Developmental methylmercury (MeHg) exposure produces response perseveration on discrimination reversal procedures, disrupts sensitivity to reinforcement, and enhances sensitivity to dopamine agonists - a profile suggesting a deficit in behavioral inhibition. To examine inhibition, we examined MeHg's effects on the acquisition and persistence of low-rate lever-pressing following a history of high-rate responding. Additionally, we examined whether chronic exposure to selenium protects against MeHg's developmental neurotoxicity. Female rats were exposed in utero via maternal exposure to drinking water containing 0 ppm, 0.5 ppm or 5 ppm of Hg as MeHg, producing approximately 0 ¦Ìg/kg/day, 40 ¦Ìg/kg/day, or 400 ¦Ìg/kg/day of Hg. The mothers (during gestation) and the offspring (throughout life) consumed a purified diet containing 0.06 ppm or 0.6 ppm of Se (as sodium selenite), forming a 2 (lifespan diet) ¡Á 3 (developmental MeHg) factorial design. Adult offspring lever-pressed under two schedules of reinforcement. A differential reinforcement of high-rate (DRH) schedule imposed rigid response requirements that remained constant through the study. A high-rate percentile schedule (PCNT-H) incorporated a flexible criterion that reinforced short interresponse times using an adjusting criterion that was sensitive to recent performance. After high-rate responding stabilized, the PCNT-H schedule was abruptly inverted by reinforcing long interresponse times. Acquisition of low-rate responding was impaired in the MeHg-exposed rats because of intrusions of high-rate response bursts. DRH response rates did not change. Dietary selenium did not influence MeHg's effects. High-rate operant behavior perseverated, suggesting that gestational MeHg exposure impairs response inhibition - an effect that extends results previously reported using choice procedures or spatial and visual discrimination reversals.