Summary
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.
Similar content being viewed by others
References
Arunlakshana O, Schild HO (1959) Some quantitative uses of drug antagonists. Br J Pharmacol Chemother 14:48–58
Cambridge D, Davey MJ, Massingham R (1977) Prazosin: A selective antagonist of postsynaptic α-adrenoceptors. Br J Pharmacol 59:514P-515P
De Mey JG, Vanhoutte PM (1980) Differences in pharmacological properties of postjunctional alpha-adrenoceptors among arteries and veins. Arch Int Pharmacodyn 244:328–329
Docherty JR, Starke K (1981) An examination of postsynaptic α-adrenoceptor subtypes in rabbit blood vessels and rat anococcygeus muscle in vitro. J Cardiovasc Pharmacol 3:854–866
Drew GM (1980) Postsynaptic α2-adrenoceptors mediate pressor responses to 2-N,N-dimethylamino-5,6-dihydroxy-1,2,3,4 tetrahydronaphthalene (M7). Eur J Pharmacol 65:85–87
Hicks PE, Cannon JG (1979) N,N-dialkyl derivatives of 2-amino-5,6-dihydroxy-1,2,3,4 tetrahydronaphthalene as selective agonists at presynaptic α-adrenoceptors in the rat. J Pharm Pharmacol 31:494–496
Langer SZ, Massingham R, Shepperson NB (1980) Presence of postsynaptic α2-adrenoceptors of predominantly extrasynaptic location in the vascular smooth muscle of the dog hind limb. Clin Sci 59:225s-228s
Langer SZ, Shepperson NB, Massingham R (1981) Preferential noradrenergic innervation of α1-adrenergic receptors in vascular smooth muscle. Hypertension (Suppl 1) 3:I112–118
Starke K, Endo T, Taube HD (1975a) Relative pre- and postsynaptic potencies of α-adrenoceptor agonists in the rabbit pulmonary artery. Naunyn-Schmiedeberg's Arch Pharmacol 291:55–78
Starke K, Borowski E, Endo T (1975b) Preferential blockade of presynaptic α-adrenoceptors by yohimbine. Eur J Pharmacol 34:385–388
Sullivan AT, Drew GM (1980) Pharmacological characterisation of pre-and postsynaptic α-adrenoceptors in dog saphenous vein. Naunyn-Schmiedeberg's Arch Pharmacol 314:249–258
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Shepperson, N.B., Langer, S.Z. The effects of the 2-amino-tetrahydronaphthalene derivative M7, a selective α2-adrenoceptor agonist in vitro. Naunyn-Schmiedeberg's Arch. Pharmacol. 318, 10–13 (1981). https://doi.org/10.1007/BF00503305
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00503305