Anatomical characterization of cytoglobin and neuroglobin mRNA and protein expression in the mouse brain

The present study aimed at characterizing the anatomical and subcellular localization of cytoglobin (Cygb) and neuroglobin (Ngb) in the mouse brain by use of in situ hybridisation, immunohistochemistry and immunoelectron microscopy. Cygb and Ngb were only found in distinct brain areas and often in the same areas. We found intense staining in the piriform cortex, amygdala, hypothalamus (medial preoptic area, supra chiasmatic nucleus, lateral hypothalamus (LH), ventromedial hypothalamic nucleus, and the arcuate nucleus, habenular nuclei, laterodorsal tegmental nucleus (LDTg), pedunculopontine tegmental nucleus (PPTg), locus coeruleus, nucleus of the solitary tract and the spinal trigeminal nucleus. In addition Cygb is found in the hippocampus, the reticular thalamic nucleus, and the dorsal raphe nucleus; Ngb is found in the sub parabrachial nucleus. Co-localization of Cygb and Ngb is mainly observed in the LDTg and PPTg. Cygb and Ngb were found in cytoplasm, along neurotubuli, in mitochondria and in the nucleus by use of immunoelectron microscopy. Most neuronal nitric oxide synthase (nNOS)-positive neurons were found to co-localize Cygb, although not all nNOS neurones contain Cygb. Ngb co-localize with almost all orexin neurons in the LH. In conclusion the distribution of Cygb and Ngb seems much more restricted and coherent than previously reported. We believe other functions than pure oxygen buffers and neuroprotectants should be considered. The anatomical data indicate a role in NO signalling for Cygb and involvement in sleep-wake cycling for Cygb and Ngb.