Figure 3: Distributions of ErbB1 mRNA and ErbB4 mRNA in rodent midbrain. In situ hybridization reveals enrichment of ErbB1 mRNA in the substantia nigra (sn) of rat pups (postnatal day 2). ErbB4 mRNA is expressed in both the sn and ventral tegmental area (vta) of mouse pups (postnatal day 2). Ip: interpeduncular nucleus. Scale bars = 250 μm.