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Age-related differences in acquisiton, steady-state performance and carbaryl effects on the operant behavior of Brown Norway rats.
Citation:
JAREMA, K., P. M. Phillips, AND R. C. MACPHAIL. Age-related differences in acquisiton, steady-state performance and carbaryl effects on the operant behavior of Brown Norway rats. Presented at Society of Toxicology (SOT) Annual Meeting, Washington, DC, March 06 - 10, 2011.
Impact/Purpose:
As part of a larger program on life-stage susceptibility, this experiment determined the effect of the carbamate pesticide carbaryl on the operant performance of young-adult, middle-age and senescent male Brown Norway rats.
Description:
The rapid increase in older adults in the population highlights the importance of understanding the role of aging in susceptibility to environmental contaminants. As part of a larger program on life-stage susceptibility, this experiment determined the effect of the carbamate pesticide carbaryl on the operant performance of young-adult, middle-age and senescent male Brown Norway rats. Rats (Charles River) were 4, 12, and 23-24 months old at the start ofthe experiment, weight-maintained, and trained to perform under a multiple variable-interval (VI) 10-sec variable-intervall 1OO-sec schedule of food reinforcement during 45-min test sessions. Once performance stabilized, one group (n=l 0-12/age) received each week a dose of carbaryl (3, 6.5 and 10 mg/kg) or com oil, p.o., 30-minutes before testing. Doses were administered in a mixed order. A second group (n=11-12/age) received weekly carbaryl (l0 mg/kg) and com oil, p.o. at 30, 60, 120 or 240 minutes before testing; treatment times were also arranged in a mixed order. During acquisition, initial response rates for the senescent rats were lower than the young-adult rats, but increased to rates higher than young adults as performance stabilized. Acquisition for middleage rats resembled young-adult rats early in training, and senescent rats late in training. Carbaryl produced dose-dependent decreases in responding, with the exception of 6.5 mg/kg in the middle-age rats. Senescent rats were overall most affected by carbaryl, especially under VI 100sec following the lowest dose. Differences in performance due to age after the highest dose (10 mg/kg) were statistically insignificant. Senescent rats, however, took the longest to recover following 10 mg/kg. Age-related differences in carbaryl effects demonstrate the importance of using a range of ages 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.)