Melanin concentrating hormone neurons modulate alcohol intake in female rats

The brain regulates choices such as when and how much food to consume, and pathway that regulate food consumption sometimes overlap with pathways that regulate intake of drugs of abuse, like alcohol. The lateral hypothalamic neuropeptide melanin-concentrating hormone (MCH) has been shown to increase ingestive behavior for both food and alcohol in male rats. Similarly, activation of the MCH neurons increases food intake, and some research has shown that these effects may depend on sex. Here, we use a rat model to investigate whether MCH neuronal signaling increases voluntary alcohol drinking and reward choice behavior in female Wistar rats. We further investigate whether the effects of MCH neuronal signaling is via an MCH receptor mediated mechanism. Results reveal that centrally administered MCH neuropeptide increases chow consumption but not alcohol drinking when either option is offered alone or when offered concurrently. By contrast, chemogenetic activation of MCH neurons increases alcohol drinking and selectively increases alcohol consumption when offered concurrently with either chow or a quinine-adulterated sucrose solution isocaloric to alcohol. Finally, pretreatment with a centrally administered MCH-1 receptor (MCH1R) antagonist had no effect on MCH neuron-mediated increases in alcohol consumption. We conclude that under the conditions tested MCH neuronal activation increases alcohol intake in females possibly through an MCH1R-independent mechanism.