Fig. 2. Dopamine concentrations and heart rates. Data for the dopamine concentrations (top ) are presented for the initial baseline concentrations, the average concentrations measured from the 7- and 10-min samples during the 10-μ· kg−1· min−1dose, the concentrations measured at the end of the first washout period, the average concentrations measured from the 30-, 60-, and 90-min samples during the 3-μ· kg−1· min−1dose, and the concentrations measured at the end of the final washout period. Heart rate data (bottom ) were recorded at the initial baseline, 8 min into the 10-μ· kg−1· min−1dose, at the end of the first washout period, 45 min into the 3-μ· kg−1· min−1dose, and at the end of the final washout period.