Abstract
The results of recent studies of the responses of developing organs to certain choline esters have suggested an important role of the nerves in the initiation and progressive development of these reactions. Armstrong 1 has shown that when the embryonic Fundulus heart is differentiated to the adult morphology but is, as yet, without nerves, injections of large amounts of acetylcholine do not inhibit contractility. After the heart has become morphologically innervated, the injection of a smaller amount of the choline compound produces a definite vagomimetic effect, as shown at first by diastolic arrest of the auricle and later by diastolic arrest of both the auricle and the ventricle. Armstrong has suggested that acetylcholine probably produces its vagus effect by stimulating the vagus postganglionic fibers and that it is effective before the intramyocardial synapses are functional. In a study, the results of which have been reported, we 2 observed that instillation of carbaminoyl choline chloride on the eye of the fetal pig kept at room temperature elicited no constriction of the iris or only a slight constriction up to a certain stage of development. After that, the response became more marked for a certain period of development, until a maximum level of constriction was reached. It was suggested that probably a choline-labile receptive substance was beginning to form through contact of nerves with muscles in fetuses when little or no constriction was observed, and that this receptive substance might be one of several structures which develop gradually during the period of increase in the constriction observed. It had been planned 2 to determine by histological studies what relation the beginning of drug action has to the development of the parasympathetic nerves and the sphincter muscle; especially, what relation the response of the receptive substance to choline esters has to the differentiation of the nerve terminations.
Get full access to this article
View all access options for this article.