Regulation of c-Fos and related proteins in the VTA by cocaine and CNTF treatments. A, Representative autoradiograms of c-Fos (58 kDa) and related proteins in the VTA 3 hr after vehicle or CNTF (0.5 μg) was infused into this brain region of control rats. Four animals were used in each treatment group with equivalent results. B, Representative autoradiograms of c-Fos and related proteins in the VTA 3 hr after CNTF (0.1 μg) was infused into this brain region of chronic saline-treated and chronic cocaine-treated rats. Four animals were used in each treatment group with equivalent results. The specificity of the resulting immunoreactivity was demonstrated by its blockade by preabsorption of the antibody with purified M-peptide antigen (Hope et al., 1994).