when the selective antagonists for beta 1 and beta 2 receptors ( beta 1-type practolol and atenolol , beta 1/beta 2-type propranolol and beta 2-type butoxamine ) were tested against isoproterenol , epinephrine and norepinephrine stimulation of ac activity , the beta 1 in contrast to beta 2 antagonists were found ineffective .
C0014563
epinephrine
C0028351
norepinephrine