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 45Ca fluxes also increased around hatching. omega-Conotoxins block > or = 80% of these 45Ca 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 45Ca 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.