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EFFECT OF AGING ON THE CARDIOVASCULAR AND THERMOREGULATORY RESPONSE TO TOLUENE IN THE BROWN NORWAY RATS.
Citation:
GORDON, C. J., P. BECKER, AND C. M. MACK. EFFECT OF AGING ON THE CARDIOVASCULAR AND THERMOREGULATORY RESPONSE TO TOLUENE IN THE BROWN NORWAY RATS. . Presented at Society of Toxicology, Seattle, WA, March 16 - 17, 2008.
Impact/Purpose:
To characterize the neurotoxicity of toluene (TOL) in aged rodents.
Description:
Since the proportion of aged in the U.S. will expand markedly for the next several decades, the U.S.EPA is assessing if the aged are more susceptible to environmental toxicants. The neurotoxicity of toluene (TOL) has been well characterized in young adults but has not been studied in aged rodents. To this end, heart rate (HR), HR variability (HRV), core temperature (Tc), and motor activity (MA) were monitored by radiotelemetry (Data Sciences, Int) in young adult (4 m), middle age (12 m) and senescent (24 m) Brown Norway (BN) rats. After 7 d of baseline monitoring in their home cages, the rats were administered TOL (0, 0.3, 0.65 and 1.0 g/kg; oral) using a cross-over design with 7 d between treatments. TOL elicited significant elevations in HR and MA and reductions in Tc. The TOL dose needed to alter HR and Tc was affected by age. There was a rightward shift in the HR dose-response in the senescent rats. TOL-induced hypothermia was greater and more prolonged with age. Baseline HR and MA were unaffected by age but daytime Tc was elevated in senescent animals. TOL increased MA but with no age interaction. Baseline HRV was elevated in senescent rats but there was no effect of TOL treatment or TOL interaction with age. The attenuated tachycardia and prolonged hypothermic response in senescent rats suggests that aging impedes recovery of autonomic processes to a toxic insult. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.