Effects of chronic ISO infusion on HR and aortic systolic, diastolic, and pulse pressures before exposure to PM. Solid lines indicate 4-h means of ISO- (black, n = 10) or saline-treated (gray, n = 11) rats, and are bordered by dashed lines indicating standard error. Stars and brackets mark periods of consistent significant differences from saline group, while individual stars indicate group differences for single 4-h means between saline and ISO-treated animals. For HR n = 13 for Saline and n = 11 for ISO, while for all pressure-derived parameters n = 9 for Saline and n=10 for ISO.