Identification of the microinjection sites in the substantia nigra (SN) (shaded areas) following post-mortem histological examination of microinjected Evans's blue (0.1 μl bilaterally). The hatched zone represents accepted microinjection sites and the squares represent microinjection sites (n=7) excluded from the results and kept as negative control for spread. A rat was considered successfully injected when both cannula tips were shown to be slightly above SN or within a distance of 0.5 mm of the SN (AP=5.3 mm posterior to the bregma) (Paxinos & Watson, 1986). Abbreviations: MS, microinjection site; SN, substantia nigra; SNC, SN pars compacta; SNR, SN pars reticulata; VTA, ventral tegmental area. Scale: 0.5 mm.