Research reportAlterations of reward mechanisms in bulbectomised rats

- First characterisation of ethanol reward mechanisms in bulbectomised rats.
- Voluntary ethanol intake was increased in bulbectomised rats.
- Bulbectomised animals needed a higher dose of ethanol to produce place preference.
- Bulbectomy led to changes in animals' reward threshold.

The positive association between alcoholism and depression is a common clinical observation. We investigated the relationship between depression and reward mechanisms using a validated animal model for depressive-like behaviour, the olfactory bulbectomy in rats.The effects of bilateral olfactory bulbectomy on reward mechanisms were studied in two different experimental paradigms - the voluntary self-administration of ethanol and the conditioned place preference to alcohol injection and compared to the effects of ethanol on locomotor activity and body core temperature. The voluntary ethanol intake was increased significantly in bulbectomised rats in a drinking experiment and also after a period of abstinence. Conditioned place preference (CPP) was induced in all animals. However, bulbectomised rats needed a higher dose of alcohol to produce CPP. The sedative effect of ethanol on locomotor activity was reduced in bulbectomised animals. Measurement of body temperature revealed a dose-dependent hypothermic effect of ethanol in both groups.These results suggest that the reward mechanisms may be altered in this animal model as a common phenomenon associated with depression. Furthermore, they support the hypothesis that the addictive and/or rewarding properties of some drugs of abuse may be modified in depression.