Binding and labeling of omega-conotoxin GVIA in crude membranes from subfractionated fractions and various areas of chick brain.

Specific binding and specific labeling of 125I-omega-CgTX were investigated in crude membranes from both subfractionated fractions and various brain areas in chick whole brain. The specific activities of the marker enzymes 2',3'-cyclic nucleotide 3'-phosphorylase, Na/K ATPase and succinic dehydrogenase in the subfractionated fractions were three- to five-fold higher than those in the P2 fraction. However, the amount of specific [125I] omega-CgTX binding in the fractions of synaptosomes and synaptic plasma membranes was only about 1.2-times higher than that in the P2 fraction. The characteristics of specific 125I-omega-CgTX labeling with disuccinimidyl suberate to the 135-kDa band were generally comparable to those of specific [125I] omega-CgTX binding sites. These results suggest that the specific binding sites of [125I] omega-CgTX were not localized the synaptosomes and synaptic plasma membranes fractions, although each fraction was well isolated from the others from which were decided by the strength of specific activity for marker enzymes.