Role of Olfactorily Responsive Neurons in the Right Dorsal Habenula - Ventral Interpeduncular Nucleus Pathway in Food- Seeking Behaviors of Larval Zebrafish


• Olfactorily responsive neurons preferentially locate in the right (R) but not left dorsal habenula (dHb).
• This right-to-left Hb asymmetry converts to a ventral-to-dorsal pattern in the downstream interpeduncular nucleus (IPN).
• Loss-of-function of either the R-dHb or ventral IPN (V-IPN) impairs food-seeking associated increase of swimming activity.
• Asymmetrical olfactory responses in the R-dHb to V-IPN pathway are important for food-seeking behavior of larval zebrafish.


The habenula (Hb) plays important roles in emotion-related behaviors. Besides receiving inputs from the limbic system and basal ganglia, Hb also gets inputs from multiple sensory modalities. Sensory responses of Hb neurons in zebrafish are asymmetrical: the left and right dorsal Hb (dHb) preferentially respond to visual and olfactory stimuli, respectively, implying different functions of the left and right dHb. While visual responses of the left dHb (L-dHb) has been implicated in light-preference behavior, the significance of olfactory responses of the right dHb (R-dHb) remains under-examined. It was reported that the R-dHb can gate innate attraction to a bile salt. However, considering a broad range of odors that R-dHb respond to, it is of interest to examine the role of R-dHb in other olfactory behaviors, especially food seeking, which is essential for animals' survival. Here, using in vivo whole-cell recording and calcium imaging, we first characterized food extract-evoked responses of Hb neurons. Responsive neurons preferentially locate in the R- but not L-dHb and exhibit either ON- (~ 87%) or OFF-type responses (~ 13%). Interestingly, this right-to-left asymmetry of olfactory responses converts into a ventral-to-dorsal pattern in the interpeduncular nucleus (IPN), a main downstream target of Hb. Combining behavior assay, we further found that genetic dysfunction or lesion of the R-dHb and its corresponding downstream ventral IPN (V-IPN) impairs the food seeking-associated increase of swimming activity. Thus, our study indicates that the asymmetrical olfactory response in the R-dHb to V-IPN pathway plays an important role in food-seeking behavior of zebrafish larvae.

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