Reports of differential DYN/KOR expression within brain reward circuitry in rodent strains that differ in preference for ethanol suggest that genetic influences may modulate the effects of DYN/KOR activity on ethanol-related behaviors. In general, rodent strains genetically predisposed to consume more ethanol appear to have reduced DYN/KOR tone relative to strains that consume less ethanol. For example, reduced DYN in the ventral tegmental area and nucleus accumbens was reported in rats selectively bred to be alcohol-preferring (AA rats) relative to their non-preferring counterparts (ANA rats) (Nylander et al., 1994; Terenius, 1994). Similarly, Lewis rats, an inbred strain that readily self-administers ethanol and other drugs of abuse, exhibit less DYN-A in the ventral tegmental area compared to the Fischer 344 inbred rat strain (Nylander et al., 1995). Ethanol-avoiding DBA/2 mice were reported to show greater DYN-A1-13 and DYN-A1-8 expression in the nucleus accumbens and caudate putamen than ethanol-preferring C57BL/6 mice (Jamensky and Gianoulakis, 1997). Similarly, DBA/2 mice also exhibited greater DYN-B in nucleus accumbens and striatum relative to C57BL/6 mice (Ploj et al., 2000). However, C57BL/6 mice were reported to have
