THE DEVELOPING CHICK BRAIN SHOWS A DRAMATIC INCREASE IN THE OMEGA-CONOTOXIN BINDING-SITES AROUND THE HATCHING PERIOD

Omega-conotoxin CVIA, a 27 amino acid neuropeptide toxin believed to target voltage sensitive calcium channels (Cruz et al., 1987, Biochemistry 26 (3), 820-824) was bound to developing chick brain at embryonic day 9-post hatch day 10. A two-fold increase was observed in omega-Conotoxin binding sites around chick hatching, embryonic days 18-20. Depolarization induced Ca-45 fluxes also increased around hatching. Omega-conotoxins block greater-than-or-equal-to 80% of these Ca-45 fluxes throughout development. Competition binding did not detect large differences in the binding affinity of sites during development. We conclude from these data that the increases in omega-Conotoxin binding sites and Ca-45 fluxes around chick hatching are related to one of the presynaptic mechanisms of neuronal maturation necessary for normal neuronal function and chick behavior after hatching.