Postsynaptic alpha 2-adrenoceptors mediate pressor responses to...

M-7 (2-N,N-dimethylamino-5,6-dihydroxy-1,2,3,4-tetrahydronaphthalene) is a potent agonist at presynaptic alpha 2-adrenoceptors in the pithed rat heart, it is also a potent vasopressor agent. The pressor effects of M-7 were unaffected by prazosin in doses much higher than were required to antagonise the pressor effects of phenylephrine, but were antagonised by yohimbine in doses lower than were effective against phenylephrine. The results suggest that the pressor responses to M-7 are mediated via postsynaptic alpha 2-adrenoceptors.