Immunohistochemical detection by immersion fixation with Carnoy solution of particular non-N-methyl-D-aspartate receptor subunits in murine hippocampus

Immunoblotting analysis revealed heterologous distribution profiles of the non-N-methyl-D-aspartate (NMDA) receptor subunits, GluR1, GluR2 and GluR6, in membrane fractions prepared from murine discrete brain structures including hippocampus. In coronal sections fixed with paraformaldehyde (PA) solution after dissection from mice perfused with 4% PA, however, no marked immunoreactivity was detected to GluR6 subunit in any hippocampal subregions, with high immunoreactivities to both GluR1 and GluR2 subunits in the strata oriens, radiatum and lacunosum-moleculare of the CA1 and CA3 subfields and the stratum moleculare of the dentate gyrus in hippocampus. In coronal, sagittal and horizontal sections fixed with Carnoy solution after dissection from animals decapitated, by contrast, high immunoreactivity was additionally detected to GluR6 subunit in the stratum lucidum of hippocampus. The systemic administration of kainate not only resulted in marked neuronal losses along the CA1-CA4 pyramidal layers 1 week later, but also led to significant decreases in immunoreactivities to GluR1, GluR2 and GluR6 subunits in the CA1 and CA3 subfields on brain coronal sections prepared by immersion fixation with Carnoy solution. These results suggest that immersion fixation with Carnoy solution may be suitable and appropriate for reproducible and quantitative immunohistochemical detection of particular non-NMDA receptor subunits in murine hippocampus.