Full and partial agonism mediated via β-adrenoceptors in chick cardiac myocytes. Data are presented as means ± SE of n = 12–20 beating groups of cells for each agonist condition. ISO, isoproterenol (a nonselective β1- and β2-adrenoceptor full agonist); Prop, propranolol (a nonselective β1- and β2-adrenoceptor antagonist, 200 nmol/l); CGP, CGP-12177A (a partial agonist at the low-affinity site of the β1-adrenoceptor).
Effect of Prop on the positive chronotropy caused by ISO. Data are presented as means ± SE of n = 12–15 beating groups of cells for each condition. The basal beating rates were 56 ± 19 and 60 ± 14 beats/min for ISO in the absence and presence of Prop (200 nmol/l), respectively.
Negative chronotropic effect of BRL-37344 in chick embryo ventricular cardiac myocytes. BRL-37344 is an agonist for the β3-adrenoceptor. Data are presented as means ± SE of n = 14–17 beating groups of cells for each condition. ***P < 0.001.
Chronotropic changes mediated via specific β-adrenoceptors. A: β2-adrenoceptor blockade with ICI-118551 (ICI) and β1-adrenoceptor-specific effects revealed by norepinephrine. B: β1-adrenoceptor blockade with CGP-20712A (CGP) and β2-adrenoceptor-specific effects revealed by epinephrine. Data are presented as means ± SE of n = 12–36 beating groups of cells for each condition. An ANOVA test showed that there was a significant variation between the conditions in A. A post hoc Tukey’s test revealed that ICI-118551 (ICI) in the presence of Prop differed significantly from both other conditions at **P < 0.01.
Cover: From material detailed in the following article: Bell FE, Wilson LB, Hoppmann RA. Using ultrasound to teach medical students cardiac physiology. Adv Physiol Educ 39: 392–396, 2015; doi:10.1152/advan.00123.2015.