Experimental study of action of hyoscine hydrobromide on development of the nervous system of amblystoma.

Abstract

The success attendant upon the treatment of post-encephalitis by hyoscine hydrobromide at various clinics, has given rise to considerable speculation as to just how the drug acts. Various suggestions will be found in the literature; the majority of which suggest the action of the drug on the basal ganglia. The careful studies of Coghill 1 on the development of the nervous system of Amblystoma punctatum have given us an excellent tool for studying the effect of drugs on the nervous system. By subjecting growing embryos to a solution of the drug it is possible to determine, with a considerable degree of accuracy, the portion of the nervous system upon which the drug acts. The experimental evidence here reported shows that the site of action of the drug can be quite sharply delimited. Young embryos of Amblystoma in the premotile stage were placed in solution of hyoscine hydrobromide in concentrations varying from 1:3,000, 1:5000, and 1:10,000. A selected series of embryos was also placed in tap water as controls. At frequent intervals, varying in length from two hours to twelve hours, the embryos were stimulated gently with a single hair. The normal progression in the development of the reflexes, as shown by Coghill, 2 occurred in both the controls and hyoscinized embryos up to the stage of the development of the swimming movement. At this time, the hyoscinized embryos either failed to respond by the usual swimming movement or gave only a flick of the tail. The controls, on the other hand, developed the swimming movements normally. Coghill's researches have correlated the functional stages in motor response to stimulation with anatomical findings in the development of the nervous system, The failure of the response of the hyoscinized embryos by swimming movements, and their almost perfect response to early reflexes, indicates beyond a doubt that the action of the drug is not on the neuro muscular mechanism, nor in the spinal cord reflex pathways, nor in the association centers in the medulla, but rather its action is on the integrative mechanism cephalad to the medulla, which controls the swimming movements.