Immunohistochemical detection of islet-1 and neuronal nitric oxide synthase in the dorsal root ganglia (DRG) of sheep fetuses during gestation.

This study first investigated the ontogeny of Islet-1 and neuronal nitric oxide synthase (nNOS) expression and their co-localization in the DRG of sheep fetuses during gestation by immunohistochemistry (IHC). The results showed that Islet-1 and nNOS were located in the nuclei and cytoplasm of DRG neurons, respectively. The relative percentages of Islet-1-immunopositive (Islet-1(+)) neurons accounting for the total DRG neurons were 90%, 79%, 66%, and 53% at days 60, 90, and 120 of gestation and postnatally, respectively. The percentage of nNOS-immunopositive (nNOS(+)) neurons was 94% at day 60 and declined to approximately 30% at day 90, with no obvious further change until the postnatal period. Dual IHC showed that approximately 69% Islet-1(+) neurons express nNOS at day 60 of gestation. This proportion declined to approximately 24% at day 90, after which there was no significant change until birth. We also observed that most Islet-1(+) and nNOS(+) neurons belonged to small and medium-sized DRG neurons from day 90 of gestation to the postnatal period. These results suggest that both Islet-1 and nNOS are important for the differentiation and maintenance of some specific phenotypes of DRG neurons during late gestation of sheep fetuses, although the related mechanisms need to be further elucidated.