Alteration in central and peripheral substance P- and neuropeptide Y-like immunoreactivity after chronic hypoxia in the rat.

The influence of long-term hypoxia on substance P (SP) and neuropeptide Y (NPY)-like immunoreactivity (LI) in discrete brain areas and peripheral structures was assessed by radioimmunoassay. Rats were exposed to normobaric hypoxia (10% O2 in nitrogen) for 14 days. In the carotid bodies of hypoxic animals, NPY-LI was significantly increased (56% vs. normoxic controls) while SP-LI was unchanged. In the brain, NPY-LI was increased in the ventrolateral medulla oblongata (23%) and in the striatum (53%); however, SP-LI was unaltered in these two regions. In the anterior pituitary, NPY-LI was increased (99%), while SP-LI was decreased (37%). No significant alteration in NPY-LI and SP-LI was observed in other discrete brain areas or peripheral structures studied. These results show that, in the rat, long-term hypoxia induces changes in NPY-LI or SP-LI in a few central and peripheral structures; these biochemical alterations may be linked to adaptative mechanisms involving morphological changes in carotid bodies or alterations in sympathetic control and neuroendocrine function.