Further characterization of the avian benzodiazepine receptor subunits including phylo- and ontogenetic aspects.

The two avian benzodiazepine binding proteins offer an opportunity for further studies concerning their regional variation and their phylo- and ontogenetic development. Accordingly, regional variation of the benzodiazepine binding proteins is investigated further in two reptiles and chicken using photoaffinity labeling with [3H]flunitrazepam followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Whereas regional heterogeneity is pronounced in chicken, it is not readily apparent in the two reptiles. The ontogeny of the benzodiazepine binding proteins in chicken forebrain and cerebellum is remarkably similar to that previously reported in rodents. The results are discussed in light of the possible existence of the gamma-aminobutyric acid/benzodiazepine receptor as an isoreceptor complex.