[Immunocytochemical demonstration of neuronal NO-synthase in rat brain cells].

The aim of the present study was to demonstrate a neuronal form of NO-synthase (type I NOS) in rat brain using immunocytochemical technique in comparison with the histochemical reaction demonstrating NADPH-diaphorase activity, as well as finding of optimal fixation protocol for the NOS demonstration. The histochemical reaction product was found to have strict cytoplasmic distribution. Immunocytochemical visualization of nNOS revealed not only cytoplasmic, but also nuclear localization of nNOS in some part of neural and glial cells without cytoplasmic nNOS staining. Searching for an optimal protocol of the material fixation and the primary antibody dilution, we succeeded in diminishing the intensity of intranuclear nNOS-like reaction while the specific cytoplasmic nNOS reaction was retained. The results obtained show that the optimal demonstration of nNOS in paraffin sections requires immersion fixation in Carnoy solution or posfixation in this solution following a perfusion with 4% paraformaldehyde solution.