Selectivity of methoctramine for muscarinic receptors in porcine cerebral arteries.

There was a clear difference in affinity (257-fold) for methoctramine between the muscarinic receptors involved in the methacholine-induced contraction of isolated pig coronary and basilar arteries, whereas atropine did not discriminate between the muscarinic receptors in these arterial smooth muscle preparations. Comparison of this finding with recent data on the selectivity of methoctramine suggests that the basilar artery contains M2 receptors whereas those in the coronary artery belong to the muscarinic receptor subtype which is present in exocrine glands (M3) and/or in ileal smooth muscle.