To rule out the possibility that electrical stimulation might have produced the concomitant stimulation of the midbrain DA neurons by current spread or trans-synaptically, the effect of repeated burst stimulation of the LC on extracellular DA and NA in the caudate nucleus and the mPFC was compared in a group of rats implanted with a microdialysis probe in the two areas. As shown in Fig. 7, each successive stimulation increased extracellular NA and DA in the mPFC in the same way as in single probe implanted rats (ANOVA results: NA: F(12,60) = 14.309, P < 0.0001; DA: F(12,60) = 7.392, P < 0.0001). During each pause, NA levels were significantly different from the previously stimulated sample, while no difference was found between DA levels (P < 0.05, Tukey-Kramer multiple comparison test).