Letter to :J&-uroscience - Anatomical Neuropharmacology Unit

Subcellular localization of GABA A receptor subunits 741Fig. 1procedure, and was more sensitive to particular conditionsthan immunoreactivity for the other subunits.Increasing concentration of glutaraldehyde (over0.05%), longer duration of fixation (over 10 min) orhigher temperature (best results were obtained withice-cold fixative) reduced the immunoreactivity probablyby altering the epitope(s). The antiserum specificfor the a6 subunit was applied to sections of ratand cat brain, but immunoreactivity could only beobserved in rat tissue. The lack of immunoreactivityin the cat may indicate that the antiserum doesnot cross-react with cat protein, although the serumwas raised to a large polypeptide containing severalpossible epitopes. However, there is no evidence yetthat the a6 subunit is expressed in cat cerebellum.Antibody bd-17 specific for the f32/3 subunits gavesimilar results in both species; antibody bd-24 specificfor the a I subunit reacted only with cat tissue. Ithas been shown that both antibodies bd-17 andbd-24 react with human, monkey, bovine and catprotein, but only antibody bd-17 recognizes the ratprotein. ll • 28 ,38 Antibody bd-24 lacks reactivity withthe rat polypeptide due to the absence of a leucineat position 4 as compared to the bovine polypeptide.8Immunoreactivity for the a6 subunit was restrictedto the granule cell layer of the cerebellar cortex(Fig. IB) in the rat brain, in agreement with the in situhybridization results. No systematic differences wereseen between the different folia in the intensity of the