Comparison through immunoblotting of glutamic acid decarboxylase (GAD) from newborn and adult rat brain

Immunochemical characterization of glutamic acid decarboxylase (GAD) from brain extracts of newborn and adult rats was investigated using a GAD antiserum that was previously raised against brain GAD from adult rats. According to the immunoprecipitation and saturation curves, no significant differences could be found as to the recognition of newborn and adult GAD by the antiserum. On immunoblots, both extracts revealed the same two immunolabelled bands (mol.wt. 59,000 and 62,000 ± 2000 Da). In both cases, the lightest band showed the strongest staining. Quantitative analysis of the immunolabelling indicated that each immunolabelled band was enriched about 10-fold in the adult brain extract. These data did not reveal any difference between newborn and adult GAD that was reminiscent of the difference found in an earlier study between GAD from lower and higher vertebrates. Whatever the regulatory mechanism responsible for the presence of two forms of GAD in the adult brain, it is already fully operative in newborn animals.