in the agonist studies clonidine and guanfacine were selective for presynaptic alpha-adrenoceptors , methoxamine and phenylephrine were selective for postsynaptic alpha-adrenoceptors and noradrenaline and alpha-methylnoradrenaline were equipotent at pre- and post-synaptic alpha-adrenoceptors .
C0028351
noradrenaline
C0025805
alpha-methylnoradrenaline