A previous study (Kimpel et al., 2007) indicated that there were significant differences in the expression of several genes in the ACB between inbred P and NP rats. However, in the present study, there were no innate differences in protein levels in the ACB-sh between the selectively bred P and NP rats. The apparent discrepancy between the gene expression data and the current protein findings may be due to a combination of factors, including: (a) differences in mRNA may not necessarily translate into similar differences in local protein levels; (b) changes in mRNA reflect changes occurring primarily in the local glial and neurons, whereas protein levels in a given region reflect both local synthesis and protein transport; and (c) the entire ACB was analyzed in the gene expression study, whereas only a sub-region of the ACB was studied in the present study.
