Olfactory dysfunction decreased local field potential in the reward system and increased EtOH consumption in mice

The relationship between olfactory dysfunction and alcohol intake is unobvious. Chronic alcohol intake results in reduced olfactory acuity and olfactory discrimination and addiction in humans. However, alcohol is a beverage with distinctive odors, which usually works as a cue to induce addictive memories and craving behavior. Whether olfactory impairment increase or decrease alcohol consumption remains an important but unclear issue. In this study, we measured ethanol (EtOH) consumption in the two-bottle choice EtOH drinking test, two bottle choice EtOH/sucrose drinking test and the drinking in the dark (DID) test during the olfactory loss. We also recorded local field potentials (LFPs) from the brain reward system, the ventral tegmental area (VTA), nucleus accumbens (NAc), and piriform cortex (Pir) one and four weeks after the induction of olfactory epithelium lesions using zinc sulfate (ZnSO₄) in mice. The results showed that the EtOH consumption and preference were increased during the period of olfactory dysfunction. 1 week after the olfactory injury, LFP powers in the reward system at low- and high-gamma bands decreased significantly, coherence between the Pir and the reward system was also decrease. 4 weeks after the ZnSO₄ treatment, LFP powers were reversed, but the coherence between VTA and NAc was decreased, indicating lasting effects post-recovery. This study demonstrates that olfactory dysfunction increased EtOH consumption in mice, which was accompanied by decreased LFP power and coherence in the reward system, which suggest that olfactory deficits changed activities in the reward system and could alter reward-seeking behaviors, which provide insights into the neurobiology of alcohol addiction.