Figure 6.
Serotonin (5-HT2A) receptor-like immunostaining is slightly lower in the XII nucleus in chronic intermittent hypoxia (CIH)- than in sham-treated rats. (A) 5-HT2A receptor-like immunostaining in the left XII nucleus and the surrounding regions, as converted to a grayscale digital image before densitometric measurements of staining intensity. The continuous white line outlines the entire XII nucleus, whereas the black line ventral to the XII nucleus encircles the reticular formation region used for measurement of background staining (bckg). The white dashed lines encircle the dorsal (XIId) and ventral (XIIv) halves of the XII nucleus. cc = central canal. (B) With no correction for CIH effect on background staining, the average intensity of 5-HT2A receptor-like staining intensity within the XII nucleus was not different between CIH- and sham-treated rats (32 pairs of brain sections from eight pairs of CIH/sham-treated rats). In contrast, background staining was significantly higher in CIH- than sham-treated rats. (C) 5-HT2A receptor-like immunostaining within the XII nucleus was positively correlated with intensity of background staining when analyzed on section-by-section basis. R = correlation coefficient for linear regression. (D) The ratio of 5-HT2A receptor-like staining intensity within the XII nucleus to background labeling was lower in CIH- than sham-treated rats, suggesting that CIH-treated rats had lower specific expression of 5-HT2A receptor-like protein in the XII nucleus than sham-treated animals (P = 0.015, paired t test).