The effects of the 2-amino-tetrahydronaphthalene derivative M7, a selective ?2-adrenoceptor agonist in vitro

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Abstract
M7 was originally reported to be a selective presynaptic α2-adrenoceptor agonist in the pithed rat preparation. Subsequent work showed that M7 also stimulated postsynaptic α2-adrenoceptors in this preparation, producing a pressor response. We have now investigated the selectivity of M7 for α2- and α1-adrenoceptors in vitro. Our results demonstrate that M7 is very potent in stimulating presynaptic α2-adrenoceptors in the rat vas deferens and postsynaptic α2-adrenoceptors in the dog saphenous vein. However, at higher doses M7 is also an α1-adrenoceptor agonist, its ED50 at α1-adrenoceptors being approximately 60 fold greater than that at postsynaptic α2-adrenoceptors. It is clear that the postsynaptic effects of M7 will depend upon the relative proportions of α1- and α2-adrenoceptors contained in the tissue under study.