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AGING AND ACTIVITY: BASELINE CHARACTERISTICS OF MOTOR ACTIVITY AND THE EFFECT OF TOLUENE IN BROWN NORWAY RATS.
Citation:
MACPHAIL, R. C., K. JAREMA, J. D. FARMER, AND V. A. BENIGNUS. AGING AND ACTIVITY: BASELINE CHARACTERISTICS OF MOTOR ACTIVITY AND THE EFFECT OF TOLUENE IN BROWN NORWAY RATS. Presented at International Neurotoxicology Association, Asilomar, CA, June 10 - 15, 2007.
Description:
The rapidly aging population raises many uncertainties regarding the susceptibility of older adults to environmental pollutants. Research to reduce these uncertainties must consider age-related changes in baseline function and its variability. For example, activity levels are generally assumed to decrease with age. It is also assumed that inter-individual variability increases with age, although this assumption has rarely been tested or quantified. Sensitivity to toxic substances is likely to increase with age due to changes in receptor sensitivity and/or metabolic capacity. We determined the influence of age on the motor activity of Brown Norway rats and their response to acute treatment with toluene. Male rats (N=5-6 per group) were obtained from the U.S. National Institute on Aging at 4, 12 and 24 months of age. Motor activity was measured during 30-minute sessions in commercial photocell test chambers that recorded horizontal and vertical activity. Rats of each age received corn oil (4 ml/kg) 30-minutes before testing for five consecutive weeks. These data were used to characterize age-related differences in baseline motor activity, including within- and between-subject variability. Weekly testing by itself did not alter baseline levels of activity in any age group. Horizontal activity and, to a greater extent, vertical activity decreased as a function of age. Baseline stability was inversely related to age. In other words, variability within and between individual rats in each age group increased with age. Toluene was next administered orally in a dose of 1000 mg/kg 30-minutes prior to a test session. Toluene increased horizontal motor activity in all age groups, but the greatest increase was obtained in the oldest rats. These results indicate age affects baseline levels of motor activity, baseline variability, and the response of Brown Norway rats to acute toluene exposure.
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