Identification of glutamatergic neurons

Abstract

Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system that gets accumulated into synaptic vesicles by vesicular glutamate transporters (vGluTs). Three isoforms of vGluTs have been cloned (vGluT1, vGluT2, and vGluT3), and shown by biochemical studies to selectively transport glutamate. The cloning of vGluTs has facilitated the anatomical and functional analysis of glutamatergic neurons, and while there are commercially available specific antibodies against vGluTs that label axonal terminals of glutamatergic neurons, the vGluT1 and vGluT2 proteins are undetectable in most cell bodies of glutamatergic neurons. Thus cellular detection of transcripts encoding vGluT1 or vGluT2 is so far the only available and reliable method to label cell bodies of glutamatergic neurons in wild-type animals. However, advances in viral cell-specific tagging of vGluTs neurons in transgenic mice has greatly facilitated the identification and manipulation of glutamatergic neurons. We will describe a multidisciplinary approach including neuronal track tracing, in situ hybridization, immuno-fluorescence, and immuno-electron microscopy that has allowed us the identification of glutamatergic neurons within the ventral tegmental area.