Development of spontaneous motility in chick embryos. Participation of the central cholinergic mechanism.

Development of the effectivensess of the systemic administration of oxotremorin (200 micrograms/kg egg weight) on spontaneous motility in chick embryos was studied from the 11th to the 19th day of incubation. 1) Oxotremorin activated spontaneous motility from the 15th day of incubation; subsequently, its effect increased with the embryo's age. 2) Glycine (100 mg/kg e.w.) blocked the activating effect of oxotremorin, again in a direct correlation to the embryo's age. 3) The spontaneous motility of spinal embryos was activated significantly less, thereby demonstrating the importance of the supraspinal component of the effect of oxotremorin. 4) The results are evaluated primarily as evidence of the role of the cholinergic mechanism (Everett 1964) in embryonal development of supraspinal control of the spontaneous activity of spinal motoneurones.