the beta-1 adrenoceptor-mediated chronotropic effects of these phenethylamines were inconsistently affected by alpha-methyl substitution , with an increase in potency being observed for alpha-methyl substitution of norepinephrine and decreases in potency being observed for alpha-methyl substitution of epinephrine and dopamine .
C0028351
norepinephrine
C0014563
epinephrine