Changes in Neuronal Expression of c-Fos Protein in the Medulla Oblongata after Unilateral Phrenicotomy in Wistar Rats

Abstract

[Purpose] The purpose of this study was to examine changes in neuronal expression of c-Fos protein in the medulla oblongata after unilateral phrenicotomy in Wistar rats. [Subjects and Methods] After left side phrenicotomy, rats were maintained for 4 weeks (test experiments), then transcardially perfused with fixatives. Brain sections were prepared, and c-Fos protein induced in neurons in the medulla oblongata was immunohistochemically stained by the ABC method. Control rats were maintained for the same period after sham operation, and the brain sections were similarly processed as in the test experiments. [Results] The number of c-Fos immunoreactive (c-Fos-ir) neurons in the medulla oblongata was counted and their spatial distributions were mapped. In both sides of the ventral respiratory group (VRG) and the left side of dorsal respiratory group (DRG), numbers of c-Fos-ir neurons were significantly increased in phrenicotomy rats compared to the control rats (P<0.05). In the right side of the DRG, the number of c-Fos-ir neurons also increased but without statistical significance. Numbers of c-Fos-ir neurons in the VRG were greater than that in the DRG. [Conclusion] The present results suggest that phrenicotomy may result in an increase in the activity of medullary respiratory neurons during the recovery of respiration after the phrenicotomy. The specific activation of the neurons in the VRG and DRG during unilateral phrenic nerve paralysis could underlie the changes in regulation of the respiratory control center following unilateral phrenicotomy.