**4. The role of the Kappa Opioid Peptide Receptor (KOP-R) in ethanol consumption and seeking**

#### **4.1 Ethanol consumption in KOP-R knockout mice**

Mice with a genetic deletion of the KOP-R (mixed C57BL/6-129SvJ background) have reduced levels of ethanol intake in animals consuming 12% ethanol and saccharin using a two-bottle choice paradigm (Kovacs et al., 2005) (Table 1). In contrast to the MOP-R and DOP-R, stimulation of the KOP-R is associated with dysphoria, suppression of reward, induced states of aversion, reduced dopamine release in the NAc, inhibition of dopaminergic neurons in the VTA and promotion of negative reinforcement (Bruijnzeel, 2009; Ebner et al., 2010; Margolis et al., 2003; Shippenberg & Herz, 1986).
