Double label immunohistochemistry for c-Fos and prodynorphin in the NAc shell. (A) Sample photomicrograph from NAc shell showing cytosolic prodynorphin immunoreactivity (brown reaction product), nuclear Fos immunoreactivity (blue open arrow, dark purple reaction product), and Fos + prodynorphin double labeling (green arrows). (B) Fos- and Fos + prodynorphin-positive cells were counted in the NAc shell, and a cell density was determined (# cells/area). Acute salvA increased c-Fos expression, but not in prodynorphin-expressing cells. *p<0.05, **p<0.01 compared to Fos group of corresponding treatment; ##p<0.01 comparing groups under the bars. Bonferroni/Dunn’s correction, N=4–6 rats/group. Abbreviations: Fos, c-Fos; DYN, prodynorphin.