Fig. 5. Absolute changes in (A,C) heart rate (fH) and (B,D) mean arterial pressure (a) in response to propranolol (A,B) and phentolamine (C,D). Asterisks represent significant (P<0.05) drug responses, and a bar that overlaps different percentages of incubation indicates that the values are statistically similar between these periods. Data are presented as means ± 1 S.E.M. N=5 for each incubation period studied.