Fig. 2: Group III mGluRs are expressed in vertebrate habenula and directly regulate neuronal membrane potential.

a, b Scatter plots show the mRNA expression of group III mGluRs in zebrafish dorsal (dHb) and ventral (vHb) habenula (a) and mouse medial (MHb) and lateral (LHb) habenula (b). c, d High-resolution spatial transcriptomics (n = 2 fish) for mGluR4 (blue), mGluR6a (red), and mGluR8b (orange) in adult zebrafish habenula (c, coronal section), and dorsal forebrain (d, horizontal section), along the dorsal-ventral (D dorsal, V ventral), anterior-posterior (A anterior, P posterior) and medial-lateral (M medial, L lateral) axes. Arrow in c points to the habenula (Hb) and arrow in (d) points to the forebrain. Box in (d) with dashed lines indicates habenula. e Left: Example image of whole-cell patch clamp recording of a zebrafish habenula neuron. Scale bar represents 10 \(\mu\)m., Membrane potential measured by whole-cell patch clamp recordings in dHb neurons of juvenile (21dpf) zebrafish brain explants, during control conditions (ACSF, light grey), with cadmium chloride (CdCl_2, 100 \(\mu\)M, dark-grey) and with CdCl₂ (100 \(\mu\)M) + L-AP4 (10 \(\mu\)M) (black). Note that group III mGluR agonist L-AP4 decreases the membrane potential of habenula neurons significantly compared to control and CdCl_2, conditions. (n = 9 fish/neurons, ACSF vs CdCl₂ p is n.s., ACSF vs CdCl₂ + L-AP4 **p = 0.0039, CdCl₂ vs CdCl₂ + L-AP4 **p = 0.0039, two-sided Wilcoxon signed-rank test.). f Membrane potential of habenula neurons during control condition (ACSF, grey) and with group III mGluR antagonist CPPG (300\(\mu\)M, pink). Note that CPPG significantly increases the membrane potential of habenula neurons compared to control conditions. (ACSF n = 37 neurons, CPPG n = 22 neurons, *p = 0.0109, two-sided Wilcoxon rank sum test.). Error bars represent mean +/- SEM. Scattered dots represent individual fish. See also Supplementary Fig. 2. Source data are provided as a Source Data file.