the negative chronotropic effect of dopamine was significantly inhibited intra-arterial phentolamine ( 2 mg ) , dihydroergotamine ( 0.4 mg ) , apomorphine ( 0.5 mg ) , haloperidol ( 0.5 mg ) , or chlorpromazine ( 5 mg ) but not by propranolol ( 0.1 mg ) or bulbocapnine ( 1 mg ) , whereas the same effect of epinephrine was significantly reduced by alpha-blockade but not by propranolol or the dopamine antagonists .
C1372752
negative chronotropic
C0033497
propranolol