Figure 4.

Expression of tyrosine hydroxylase mRNA in the ventral midbrain of CB1^+/+ and CB1^−/− animals. (A) Film autoradiograms depict CB1 (Left) and tyrosine hydroxylase expression (Right) in coronal brain sections containing the substantia nigra and ventral tegmental area for the two genotypes. Note the absence of CB1 mRNA expression in the area of tyrosine hydroxylase labeling (dopamine neurons) in wild-type (+/+) animals. The substantia nigra pars reticulata (SNr) was outlined by using Nissl-stained and GAD 67-labeled adjacent sections. HC, hippocampus; IP, interpeduncular nucleus; SNc, substantia nigra pars compacta; VTA, ventral tegmental area. (B) Mean density (mean ± SEM) (Left) and area (number of pixels with density values above background) (Right) for tyrosine hydroxylase expression in the substantia nigra/ventral tegmental area are given for CB1^+/+ (n = 7) and CB1^−/− mice (n = 7). Gene expression was measured in sections from seven rostrocaudal levels, and average values are presented.