Cholinomimetic teratogens: studies with chicken embryos.

The cholinomimetic compounds carbachol, decamethonium, neostigmine, succinylcholine, trimethylphenylammonium, and others were tested for their interference with normal chick development. All these compounds led to abnormalities of the cervical vertebrae; at higher dosage interference with normal morphogenesis involved the whole vertebral column. Hypoplasia of the leg muscles occurred with lower incidence. Responses, tested with carbachol, rose from 24 to 72 and 96 h, then declined to 120 h of incubation. Two of the cholinometic compounds used in combined treatment produced a high degree of synergism. Gallamine, benzoquinomium, butyrylcholine, and bethanechol had protective effects. Acetylcholine, at high dosage, caused defects different from the above. It is suggested that the cholinomimetic teratogens interfere with normal development by displacing acetylcholine from its receptors or by forming complexes with it.