clonidine ( 5.3 x 10 ( -6 ) m ) , a selective presynaptic-adrenoceptor ( alpha 2-receptor ) stimulant failed to produce hyperpolarization , however , phenylephrine ( 5 x 10 ( -5 ) m ) a pure postsynaptic alpha-adrenoceptor ( alpha 1-receptor ) stimulant produced a similar effect as adrenaline .
C0034783
adrenoceptor
C0034784
alpha-adrenoceptor