Glycine-and gaba-ergic elements in the development of embryonic spontaneous motility.
Relationships between the activating effect of strychnine [1 mg.kg-1 egg weight] and picrotoxin [1 mg.kg-1 e.w.] and the inhibitory effect of glycine [100 mg.kg-1 e.w.] and gamma-aminobutyric acid [100 mg.kg-1 e.w.] were studied in normal and spinal 15- and 17-day chick embryos. All the substances were applied onto the embryonic membranes and the spontaneous motor activity of the embryos served as indicator. The combined administration of the two convulsants evoked successive activation of spontaneous motility, with an early strychnine phase and a late picrotoxin phase. In the older embryos, the supraspinal parts of the brain were found to play a greater role in the activating effect of the two substances than in 15-day embryos. Study of the interrelationship of the two activators and the inhibitory amino acids failed to show specific relationships of an adequate degree. Simultaneous administration of the two inhibitory amino acids was followed by summation of their inhibitory effect on combined strychnine and picrotoxin activation. As the CNS developed, the effect of their reciprocal interaction shifted increasingly to the supra-spinal compartments of the brain. The results provided further evidence of the significance of the last phase of the chick embryo's development for the effective linking up of inhibitory mechanisms in the formation of embryonal behaviour.
D000818:Animals; D001921:Brain / Q000187:drug effects; D002642:Chick Embryo / Q000187:drug effects*; D005998:Glycine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D010852:Picrotoxin / Q000494:pharmacology; D013331:Strychnine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D005998:Glycine; D010852:Picrotoxin; D013331:Strychnine; D005680:gamma-Aminobutyric Acid