Fig. 2. Time course of norepinephrine release induced by 10−2m (top ) or 10−4m (bottom ) nicotine (open circles) or metanicotine (closed circles), continuously perfused in microdialysis probes in the spinal cord dorsal horn. Each point represents the mean ± SE of five to seven animals. *P < 0.05 compared with peak drug effect by predrug infusion by one-way repeated-measures analysis of variance on the raw data.