Immunocytochemical evidence for the localization of the GM1 ganglioside in carbonic anhydrase-containing and RT 97-immunoreactive rat primary sensory neurons.

Localization of GM1 ganglioside, the receptor for cholera toxin, and choleragenoid, which is the binding subunit of cholera toxin, was studied in the rat L5 dorsal root ganglion. Sections were incubated with choleragenoid and treated immunocytochemically. Choleragenoid-like immunoreactive cells were then examined for possible co-localization with carbonic anhydrase-like, RT 97 (antibody to neurofilament proteins), substance P-like, somatostatin-like and calcitonin gene-related peptide-like immunoreactivity and fluoride-resistant acid phosphatase (FRAP) activity, using adjacent sections. A subpopulation of dorsal root ganglion neurons exhibited choleragenoid-like immunoreactivity. The majority of these were medium-sized and large neurons. The strongest immunoreactivity was found in the area of the plasma membrane, but strong reactivity was also seen in the cytoplasm. The majority of the choleragenoid-like immunoreactive cells showed carbonic anhydrase-like and RT 97 immunoreactivity. Cells showing co-localization of choleragenoid-like and neuropeptide-like immunoreactivity or activity for FRAP were rarely observed. Our results suggest that the GM1 receptor is localized primarily on carbonic anhydrase-containing and RT 97-immunoreactive primary sensory neurons.