however , after removal of spare postsynaptic vascular alpha-1 adrenoceptors by treatment with the irreversible alpha adrenoceptor antagonist phenoxybenzamine , the alpha-1 adrenoceptor-mediated pressor response of cirazoline became highly sensitive to antagonism by diltiazem and resembled in this regard alpha-2 adrenoceptor-mediated vasoconstriction for which no receptor reserve exists .
C0034784
alpha adrenoceptor
C0001638
alpha-1 adrenoceptor