in elevated DYN mRNA and peptide levels in the paraventricular nucleus of the hypothalamus in rats (Chang et al., 2007). Elevated prodynorphin levels were reported in the nucleus accumbens of rats with a 1-month history of drinking ethanol (Przewlocka et al., 1997). Similarly, in rats injected with ethanol (2 g/kg) for 13 days, DYN-B was upregulated in the nucleus accumbens 30 minutes later and 21 days later (Lindholm et al., 2000). In contrast to these reports of elevated expression of the opioid peptide, repeated ethanol (2 g/kg) injections over 14 days reduced KOR mRNA expression in the nucleus accumbens and ventral tegmental area (Rosin et al., 1999).
