Effect of indole alkaloids from Gardneriagenus and Uncaria genus on neuromuscular transmission in the rat limb in situ.

Abstract
Effect of 6 indole alkaloids and 1 synthetic compound on neuromuscular transmission was examined in the rat limb preparation in situ. Gardneramine inhibited the gastrocnemius contractions elicited by electrical stimulation of the sciatic nerve, but exerted little or no inhibition on the contractions elicited by direct stimulation of the muscle. The inhibitory effect of gardneramine was a little stronger than that of hexamethonium and was very weak when compared with that of d-tubocurarine. Gardnerine augmented both contractions elicited by nerve and muscle stimulation. Gardnutine, hydroxygardnutine, hirsutine and 1 synthetic compound showed a long-lasting depressive effect on both contractions, while isorhynchophylline was little effective. Only gardneramine affects mainly neuromuscular transmission.