Punishment of ethanol choice in group-housed male cynomolgus monkeys

Abstract

Background

A common characteristic of individuals with alcohol use disorder (AUD) is that they continue to consume alcohol despite adverse consequences. A better understanding of the factors that influence this relative insensitivity to punishment may help identify novel treatments for AUD. In animal models, this characteristic can be studied by adding the bitter-tasting alkaloid, quinine, to an ethanol solution. In the present study, punishment of ethanol drinking was assessed in socially housed male cynomolgus monkeys to determine whether sensitivity to punishment is influenced by a monkey’s position in the social hierarchy. Methods: Ten adult male cynomolgus monkeys with 4.5 years of experience drinking ethanol were given concurrent access to a 4 % ethanol solution and a 0.5 % Tang solution for 3 h each day, 5 days per week. When ethanol choice was stable, a single quinine concentration (0.003–5.6 g/L) was added to the ethanol solution for one day. This was repeated until a full quinine concentration-effect curve was created. Results: Addition of quinine produced a concentration-dependent decrease in ethanol choice and intake. The potency of quinine to decrease ethanol choice did not differ significantly between socially dominant and socially subordinate monkeys. However, only in dominant monkeys were significant positive relationships found between quinine EC₅₀ values and both the volume of ethanol consumed at baseline and baseline ethanol intake.

Conclusions

These results demonstrate the ability of quinine to produce robust punishment of ethanol choice and suggest that the chronic subordination stress experienced by the low-ranking monkeys alters sensitivity to punishment.