Abstract: The postnatal development of the γ‐Aminobutyric acidA/benzodiazepine receptor (GABAR/BZDR) complex of the rat brain has been investigated using the monoclonal antibody 62‐3G1 and the polyclonal rabbit antiserum A, specific for the 57,000 and 51,000 Mr, receptor subunits, respectively. Both GABAR and BZDR binding activities co‐precipitated during all postnatal ages. Adult rats showed a main 51,000 Mr [3H]flunitrazepam photoaffinity‐labeled peptide, whereas newborn rats showed several photolabeled peptides of higher Mr. All the photolabeled peptides could be immunoprecipitated with each antibody regardless of the age of the rats. These results suggest that the physical coupling between the GABAR and the BZDR is already present in newborn animals and it is maintained afterwards during development. Glycosidase and peptidase treatments of the immunoprecipitated GABAR/BZDR complex indicated that all the [3H]flunitrazepam‐photolabeled subunits are different peptides, although they seem to conserve a high degree of homology. In addition to the age‐dependent heterogeneity, the results also suggest that for each age, there is heterogeneity in the subunit composition of the GABAR/BZDR complex.
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