Normal Closure of Secondary Palate in Paralyzed Mouse Embryos

Muscle relaxants, anesthetics, and central nervous system depressants administered to pregnant mice before and during the criti-cal period of palate closure showed no teratogenic effects on palate formation. These findings indicate that muscular activ-ity is not essential for normal palate closure. The mechanism of palate closure and the etiology of cleft palate have not been well understood, despite extensive experimental work in the field of teratology.'-8 In fact, a number of articles that have appeared in the literature during the past few years9-"1 signify a regressive trend toward the old notion of His,12 Poelzl,13 and Inouye'4 that embryonic movements, such as extension of the neck or opening of the mouth, are es-sential for normal closure of secondary palate. This attractive hypothesis has been re-pudiated in the past3 and, most recently, has been challenged again on the basis of experimental evidence recorded on mice subjected to paralytic action of various muscle relaxants and central nervous sys-tem depressants.'5"16 The present study rep-resents an effort to explore the validity of "muscular movement " theory on the inbred strain of A-Jax mice that is known to be highly susceptible to cleft palate formation. Materials and Method