Strain differences in the expression of dopamine D1 receptors in Wistar-Kyoto (WKY) and Wistar rats.

The Wistar-Kyoto (WKY) rat is a stress-sensitive strain that is prone to depressive-like behavior in various experimental paradigms. While recent work has highlighted a role for dopamine (DA) in the pathology of depression, research on the WKY rat has also suggested that dysfunction of DA pathways may be an important component of the behavior in this strain. Previous work has demonstrated differential patterns of DA transporter sites, DA D2 and D3 receptors in WKY rats compared to control strains. To further this work, the present study utilized autoradiographic analysis of [3H]-SCH23390 binding to DA D1 receptors in various brain regions of naïve male WKY and Wistar (WIS) rats. The results revealed a significant strain difference, with WKY rats demonstrating lower D1 binding in the caudate putamen and regions of the nucleus accumbens (p<0.05). An opposite pattern was found in the substantia nigra pars reticulata where D1 binding was higher in WKY rats compared to WIS rats (p<0.05). Because the D1 receptor represents a critical site where DA acts to modify behavior related to depression, the altered expression of this receptor in the WKY rat found in the present study may be reflective of the depressive susceptibility noted in this strain.