Abstract
The effects of six indole alkaloids on parasympathetic ganglionic transmission were studied in a preparation of the guinea pig urinary bladder in situ. The effect of hirsutine on spontaneous movement of the organ was also examined. Among these alkaloids, gardneramine and hirsutine most potently inhibited the contraction of the urinary bladder induced by electrical stimulation of the pelvic nerves. Their potency was about one-half of that of hexamethonium. The effect of gardneramine was of short duration. Both alkaloids depressed the contraction induced by intraarterial dimethylphenylpiperazinium, with no antagonizing action to the acetylcholine-induced contraction. Hirsutine showed a local anesthetic action in the isolated frog sciatic nerve preparation, while other alkaloids had only a weak effect. Hirsutine, isorhynchophylline, and gardnerine elevated the tone of the spontaneous movement of the organ and augmented its amplitude. The stimulating action of hirsutine was not affected by pretreatment with tetrodotoxin, atropine, diphenhydramine, or hexamethonium.
