The effect of retinoic acid (RA) on the development of the inner ear was examined in mouse embryos. Embryos were injected with RA into the left inner ear on day 13 of gestation (E13), after which they continued to develop exo utero until E18. The inner ears were then examined histologically. One of the four embryos in the RA-injected group had a deformed saccule, whereas no abnormality was seen in the controls, but it is not clear that this deformity was specifically caused by RA. This

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... tal system with further modifications appears to be useful in the examination of the molecular aspects in the development of the inner ear and in the development of animal models for congenital defects of the inner ear.