Fromthe dried buds of Magnolia salicifolia MAXIM, d-coclaurine (1), d-reticuline (2), 1-N-methylcoclaurifle (3) and yuzirine (4) were isolated. Fifty percent inhibitory doses (1iM) in acetyicholine (ACh, 27.5 tM)-induced contraction of frog skeletal muscle were as follows: d-tubocuraine (d-TC) 3.09, 2 93.2, 3211, 1 467 and 4 more than 945. 4 (94.5 and 315 tM) increased the ACh-induced contraction. Indirectly stimulated twitching of frog nerve-muscle preparations were completely blocked by the following doses (.tM): d-TC 1.47, 1 31.1, 2 239 and 3 more than 257. 1, 2 and 3 did not or only slightly block directly stimulated twitching. In contrast 271 1tM 4 blocked the directly stimulated twitching.