Development of spontaneous motility in chick embryos. The effect of drugs influencing central aminergic systems.

The development of changes in spontaneous motor activity after the systemic administration of substances interfering with the function of central aminergic systems was studied in 11- to 19-day chick embryos. Reserpine was administered in a dose of 2.5 mg/kg egg weight, chlorpromazine in a dose of 3 mg/kg e.w. and dehydrobenzperidol in a dose of 6 mg/kg e.w. to the embryonal membranes. The effect of reserpine was studied for 4 hours and the effect of chlorpromazine and dehydrobenzperidol for 60 min after administration. None of the above substances produced significant changes in the frequency of spontaneous movements up to the 13th day of incubation. From the 15th day they began to depress spontaneous motility, the intensity and duration of which increased with the embryos' age. Reserpine had the strongest effect. The results are interpreted with reference to development of the participation of central aminergic systems in supraspinal control of spontaneous motility in chick embryos in the second half of embryogenesis. They are further evidence of the integration of aminergic systems after the 15th day of incubation.