Catharanthine ((+)-3,4-Didehydrocoronaridine) suppresses nicotinic receptor-mediated diaphragm contractions with an IC50 of 59.6 μM.

nAChR:59.6 μM

Catharanthine evokes a concentration-dependent attenuation of carbachol responses in the rat ileum preparation, producing rightward curve displacements and decreases in maximal agonist responses. The mixture of serpentine, plus ajmalicine and catharanthine reveals a concentration-dependent inhibitory effect of acethylcholinesterase (AchE), with an IC50 at ca. 2.25 μg/mL. [1] Catharanthine can induce the self-association of tubulin into linear indefinite polymers with an efficacy that is 75% that of vinblastine or vincristine. Catharanthine binds to tubulin alpha-beta dimer with binding constant of 2.8 mM. [2] Catharanthine stimulates release of amylase from pancreatic fragments and to cause extensive degranulation of pancreatic acinar cells with accumulation of membrane material in the Golgi region. Catharanthine induces a delayed release of Ca2+ from prelabeled pancreatic fragments as compared to bethanechol. [3] Catharanthine inhibits epibatidine-induced Ca(2+) influx in TE671-α, -β, -γ, -δ cells in a noncompetitive manner with similar potencies IC50 of 17 mM-25 mM. Catharanthine inhibits [3H]TCP binding to the desensitized Torpedo AChR with higher affinity compared to the resting AChR. Catharanthine enhances [3H]cytisine binding to resting but activatable Torpedo AChRs, suggesting desensitizing properties. [4]