Single cell quantitative immunocytochemistry of cyclic GMP in the superior cervical ganglion of the rat.

In the superior cervical ganglion of the rat, using a newly developed antiserum against formaldehyde-fixed 3',5'-cyclic guanosine monophosphate (cGMP), cGMP immunoreactivity was observed in the large postganglionic neuronal cell bodies; no cGMP-immunofluorescence was found in nuclei or in satellite cells, glia or fibroblasts. In vitro incubation of ganglia in media with high K+ (up to 100 mM) or carbachol (10(-8)-10(-5) M) showed an increase only in cGMP-immunofluorescence in the large postganglionic cell bodies. The intensity of the immunofluorescence was taken as a measure for cGMP-immunoreactivity and was quantitated using a Leitz MPV-II system. Dose-response curves were constructed for the increase in cGMP-immunofluorescence intensity for K+ and carbachol. The carbachol stimulated cGMP-immunofluorescence intensity was antagonized competitively by atropine, whereas the high K+ stimulated cGMP-immunofluorescence intensity was not. Hexamethonium (10(-6) M) was without effect on the carbachol stimulated cGMP-immunofluorescence intensity. The morphological and pharmacological data indicate that we developed a very specific procedure for quantitative immunocytochemistry of cGMP in tissue sections. This technique makes it possible to use cGMP-immunofluorescence intensity as a postsynaptic parameter in individual cell bodies in heterogeneous tissue.