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One particular region of zebrafish brain can provide an understanding of the circuitry underlying the nicotine addiction, a new study finds.

In neural pathways researches, it is helpful in establishing an analogous relationship between a region of the human brain and the brains of a bit less complex and studied animal species.

A bit less understood and difficult-to-access part of the brain called mammalian habenular nuclei is responsible for the regulating dopamine and serotonin. These two neurotransmitters are involved in motor control, mood, learning and addiction.

The habenular nuclei of fish, unlike mammalian habenulae, are located dorsally. This placement makes it one of those easily accessible and hence studied parts. Unfortunately it was unclear that whether zebrafish habenular neurons produced neurotransmitter acetylcholine. Acetylcholine is enriched in this region of the mammalian brain and activates the same receptors which nicotine is known to bind.

The recent study has confirmed that the pathway between the habenula and a different part of the brain called the mildbrain interpenduncular nucleus utilizes acetylcholine in zebrafish. The same is the case with humans. The study has also shown that there is a left-right difference in this part of the fish brain.

“Our work demonstrates broader uses for zebrafish in studying the function of the habenula and addresses a major weakness in the field, which was the poor characterization of neurotransmitter identity in this area,” said lead author Elim Hong in the press release. “Going forward, these results will help us study how brain circuitry influences nicotine addiction.”

The developments of the study is published in the December 9 issue of Proceedings of the National Academy of Sciences.