Expression of vesicular glutamate transporter 3 mRNA in the brain and retina of the pigeon

• Sequence of vGluT3 cDNA of the pigeon brain and retina is analyzed.
• VGlut3 is expressed in neurons of caudal linear nucleus (LC) and in amacrine cells.
• A small population of vGluT3 cells in LC and retina are serotonin immunoreactive.
• VGluT3 is present in the avian brain and retina as well in mammals.

Vesicular glutamate transporters (vGluTs), which accumulate glutamate into synaptic vesicles, are classified into three subtypes in mammalian brains: vGluT1, vGluT2, and vGluT3. VGluT3 is localized in non-glutamatergic neurons of the brain and retinal amacrine cells. In birds, the vGluT3 genome is found, but its distribution in the brain or retina is unknown. The present study was conducted to analyze vGluT3 cDNA sequence and elucidate its distribution in the pigeon brain and retina. The vGluT3 cDNA comprises 1761 bp and showed 95% and 88% identity to the chicken and zebra finch vGluT3 cDNAs, respectively, and 74% identity to human vGluT3 cDNA. In situ hybridization revealed that the vGluT3 mRNA was expressed in neurons of the caudal linear nucleus (LC) of the brain and in amacrine cells of the inner nuclear layer of the retina. A combination of in situ hybridization and serotonin immunohistochemistry revealed three types of stained cells in LC and retina: vGluT3+/serotonin+, vGluT3+/serotonin−, and vGluT3−/serotonin+. The vGluT3+/serotonin+ cells were approximately 22% in LC and 16% in the retina. The present results suggest that the pigeon vGluT3 mRNA is comparable with the mammalian type.