FIGURE 6.

Differential inhibition of nicotine-induced desensitization by CST variants. PC12 cells preloaded with [³H]norepinephrine were challenged with a concentration of 30 μm nicotine for 10 min with/without increasing concentrations (0.1–10 μm) of the CST variants. Cells were washed 2 times with secretion buffer and then rechallenged again with the agonist (30 μm nicotine) without peptides. After 10 min, cells were harvested for measurement of norepinephrine release in the media and cell lysate. Data were expressed as % increments (mean ± S.E.) in norepinephrine secretion due to CST peptides with respect to the untreated (without CST peptides) condition. Results of two-way ANOVA are shown, factoring for the effects of peptide, concentration, and peptide-by-concentration interaction on the norepinephrine secretion. * and ** indicate p < 0.05 and p < 0.01 with respect to CST-Ser-364, whereas # and ## indicate p < 0.05 and p < 0.01 with respect to CST-Val-367 (by two-tailed t test).