The delta2-opioid receptor antagonist naltriben selectively attenuates alcohol intake in rats bred for alcohol preference

The relative importance of different opioid receptor types in mediating alcohol drinking behavior compared with the intake of other ingesta can be determined by characterizing the effects of selective opioid antagonists on the intake of various ingesta. Nonselective opioid receptor antagonists suppress the intake of many ingesta including alcohol, food, water, and sweets. Two distinct subtypes of delta-opioid receptors, delta 1 and delta 2, have recently been identified in rodent brain. We have previously reported that naltrindole (NTI), which blocks both delta 1 and delta 2 receptors, suppresses both alcohol and saccharin intake in rats selectively bred for high alcohol preference (P line). We now report that naltriben (NTB), an opioid antagonist that is selective for delta 2-opioid receptors, suppresses alcohol intake in rats of the P line and the effect appears to be both specific for alcohol and independent of alcohol palatability. NTB may reduce alcohol intake by attenuating the reinforcing pharmacological properties of alcohol.