Identification of GABAergic neurons innervating the zebrafish lateral habenula

Abstract

Equations: 0 Total number of words: 5191 Number of words in abstract: 177 2 Abstract Habenula neurons are constantly active. The level of activity affects mood and behaviour, with increased activity in the lateral habenula reflecting exposure to punishment and a switch to passive coping and depression. Here, we identify GABAergic neurons that could influence activity in the lateral habenula of larval zebrafish. GAD65/67 immunohistochemistry and imaging of gad1b:DsRed transgenic fish suggest the presence of GABAergic terminals in the lateral habenula. Retrograde tracing with the lipophilic dye DiD indicates that this GABAergic innervation derives from the thalamus and a nucleus lateral to the posterior tuberculum, the putative M2 nucleus. Two-photon calcium imaging indicates that blue light causes excitation of thalamic GABAergic neurons and concomitant inhibition of a subpopulation neurons in the lateral habenula. Whole-cell recording confirmed that blue-light induced hyperpolarization of lateral habenula neurons. No response to blue light was detected in the putative M2 neurons. These observations suggest that GABAergic input from the thalamus mediates inhibition of the zebrafish lateral habenula, possibly contributing to the beneficial effects of blue light. Stimuli acting via the putative preglomerular complex remain to be defined.