Development of pentazol (metrazol) activation of spontaneous motility in chick embryos.

The effect of pentazol (100 mg.kg-1 egg weight) on the spontaneous motility of normal and spinal chick embryos was studied from the 11th to the 19th day of incubation. Pentazol already activated embryonal motility, with two maxima, in 11-day embryos. Subsequent development was chiefly quantitative, especially in the first activation maximum. From the 15th day of incubation supraspinal compartments of the CNS participated significantly in pentazol activation. After the 15th day pentazol activation of spontaneous motility was inhibited by glycine- and GABA-ergic factors. The results before and after the 15th day of incubation are evaluated from the aspect of the mechanism of the action of pentazol on the central motor apparatus during embryonal maturation of the CNS.