A hormone produced by immune cells can alter motivation for cocaine, but not other rewards, shows a mouse study published this week in Nature Communications. The study goes on to show that this effect is modulated by a brain region that plays a central role in reward processing. These findings represent a possible therapeutic approach to decrease a cocaine addict’s motivation to seek cocaine without the potential for abuse.
Previous research has established a link between cocaine use and the immune system, with addicts showing altered immune responses to drug cues. In this study, Drew Kiraly and colleagues identify granulocyte-colony stimulating factor (G-CSF) - a hormone produced by immune cells - as a naturally occurring substance that is upregulated in mice who have been exposed to cocaine. Injecting G-CSF into the nucleus accumbens, a brain region associated with reward, causes mice to take more cocaine. This injection did not change motivation to consume a more natural reward, sugar water. However, injecting an antibody that neutralizes G-CSF in this same brain region (the nucleus accumbens) can reduce the mouse’s motivation to take cocaine.
Taken together, the results from this study suggest that manipulating G-CSF in the reward center of the brain changes the biochemical signals that lead animals to take cocaine.