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Age-related behavorial changes in methomyl effects on the behavior of labroatory rats: Comparison of operant behavior nad motor activity
Citation:
Jarema, K., P. Phillips, AND R. Macphail. Age-related behavorial changes in methomyl effects on the behavior of labroatory rats: Comparison of operant behavior nad motor activity. Presented at Society of Toxicology Meeting, March 10 - 14, 2013.
Impact/Purpose:
This abstract will be presented at the Society of Toxicology meeting March 10-14, 2013, in San Antonio, Texas
Description:
The rapid increase in older adults in the population highlights the importance of understanding the role of aging in susceptibility to environmental contaminants. Methomyl is a cholinesteraseinhibiting carbamate pesticide used on a variety of produce. Although the effects of pesticides have been widely studied, little is known about changes in susceptibility with advancing age. This experiment compared the effects of methomyl on both operant behavior and motor activity in young-adult (4mo), middle-age (1 2mo) and senescent (24mo) male Brown Norway rats. Methomyl was dissolved in deionized water (vehicle) and administered orally. Subjects were trained to perform under an operant multiple variable-interval 10-sec variable-interval 100-sec food reinforcement schedule; the dose-response group received weekly doses of methomyl (0, 0.5, 1.0, 1.5, and 2.0 mg/kg) 15 minutes before testing, while the recovery group received weekly methomyl (1.5 mg/kg) at 15, 45, 90 and 180 minutes before testing. Horizontal and vertical locomotor activity testing occurred at weekly intervals; the dose-response group received methomyl (0, 0.5, 1.25, 2.0 and 2.75 mg/kg) 15 mm prior to testing and recovery group received methomyl (2.5 mg/kg) 15, 45, 90 and 180 mm prior to testing. Under all conditions, doses and treatment times were arranged in a mixed order. Methomyl produced dose-related decreases in both operant behavior and motor activity. Senescent rats were generally most affected by methomyl, for both operant behavior and motor activity, and had lower ED5O values than the younger age groups. For operant behavior, recovery time varied little between the different age groups. However, for motor activity, senescent rats were initially slower to recover than were younger age groups. These age-related differences in the effects of methomyl demonstrate the importance of using multiple life stages in order to make informed inferences about toxicant susceptibility and risk. (This is an abstract of a proposed presentation and does not reflect US EPA policy.