The first aim of this study was to determine the cellular distribution of NR1 in the piglet brainstem. Documentation of NR1
mRNA was by non-radioactive in situ hybridisation (non-RISH) and of NR1
protein by immunohistochemistry. We found that all neurons expressed
mRNA but not all had NR1
protein. Application of non-RISH has permitted us, for the first time, to document the cellular localization of NR1
mRNA showing that it was present in the cytoplasm and nucleolus of motor neurons but dispersed throughout the cellular compartments of sensory neurons. NR1
protein on the other hand, was localized to the cytoplasm only. The second aim of this study was to quantify the distribution of NR1
mRNA and
protein. Using image analysis software, we used optical density (OD) to quantify the non-RISH signal for
mRNA and cellular counting for
protein (expressed as % positive). Results show that NR1 expression is greater in motor than sensory nuclei; for
mRNA: 0.46+/-0.04 vs. 0.31+/-0.02 OD units (P<0.001), for
protein: 75.9+/-3.1 vs. 58.4+/-2.5% positive (P<0.001). The third aim of this study was to determine the effects of intermittent hypercapnic
hypoxia (IHH) on NR1 expression. Chronic IHH exposure caused differential changes in
mRNA and
protein expression. NR1
mRNA expression increased while the number of neurons expressing NR1
protein showed no change. This finding suggests that
NMDA pathways are activated by exposure to IHH.