Fig. 3. Representative photomicrographs of double fluorescent staining. Sections of the pontine noradrenergic nuclei, i.e. , locus caeruleus (a, d [low magnification]), A7 (b, e [high magnification]), and A5 (c, f [high magnification]), were stained for both c-Fos and dopamine β-hydroxylase after exposure to air (a–c ) or N2O (d–f ).