Elsevier

Neuroscience

Volume 123, Issue 4, 2004, Pages 983-1002
Neuroscience

Localization of VGLUT3, the vesicular glutamate transporter type 3, in the rat brain

https://doi.org/10.1016/j.neuroscience.2003.10.039Get rights and content

Abstract

We have recently identified a third subtype of glutamate vesicular transporter (VGLUT) named VGLUT3. In the present study, we provide a detailed account of the regional and cellular distributions of VGLUT3 in the rat brain, using specific nucleotide probes and antisera. The distribution of VGLUT3 protein was compared with that of the other vesicular transporters (VGLUT1 and VGLUT2). All the areas expressing VGLUT3 also contain high levels of VGLUT1 and -2 proteins, but, at a finer level of analysis, the distribution of the three subtypes differs. Unlike VGLUT1 and -2, VGLUT3 expression is limited to discrete cell populations. Neurons containing VGLUT3 transcript are essentially observed in the caudate-putamen, the olfactory tubercle, the nucleus accumbens, the hippocampus, the interpeduncular nucleus and the dorsal and medial raphe nuclei. More scattered populations of VGLUT3 expressing neurons are found in the cerebral cortex. The distribution of the VGLUT3 protein, as determined with specific antisera, overlaps with that of the transcript in the caudate-putamen, olfactory tubercles, hippocampus, cortex, interpeduncular nucleus, and raphe nuclei, suggesting that VGLUT3 is essentially present in local projection neurons in these regions. Microscopic examination reveals staining of terminals and perikarya. Furthermore, co-localization studies indicate that VGLUT3 is present in GABAergic interneurons in the hippocampus, as well as in the interpeduncular nucleus. However, other regions, such as the substantia nigra (pars compacta), the ventral tegmental area, and the parabigeminal nucleus, receive a dense VGLUT3 terminal labeling although they do not contain VGLUT3 expressing neurons. In these regions, VGLUT3 immunoreactivity may be present in terminals of long projecting neurons. This subclass of glutamatergic afferents differs from other “classical” excitatory terminals that express VGLUT1 or VGLUT2.

The distribution of VGLUT3 in the rat brain suggests an unsuspected function of vesicular glutamate transport in subsets of interneurons and in neuromodulatory neurons.

Section snippets

Animals

Adult male Sprague–Dawley rats (200–300 g) were housed in an animal room on a 12-h light/dark cycle with food and water ad libitum. All efforts were undertaken to minimize the animal number used in the course of experiments and their suffering. All the procedures involving animals and their care were conducted in conformity with the institutional guidelines that are in compliance with national and international laws and policies (European Comunity Council directive 87-848, October 19, 1987,

General comments

We analyzed VGLUT3 mRNA and protein distributions in the rat brain by three different methods: in situ hybridization, immunoautoradiography and immunohistochemistry.

VGLUT1, -2 and -3, the three subtypes of VGLUTs, have highly conserved nucleic acid and peptidic sequences. Most of the divergences occur in their 5′ and 3′ translated and untranslated regions, whereas the core of the open reading frame bearing the trans-membrane domains is highly conserved (Aihara et al., 2000, Ni et al., 1994,

Discussion

The absence of specific molecular markers of glutamatergic neurons has long hampered the elucidation of their anatomic distribution. The recent discovery of the VGLUTs family (Aihara et al., 2000, Bellocchio et al., 2000, Ni et al., 1994, Takamori et al., 2000) has allowed considerable progress to be made in the understanding of excitatory pathways and has opened the way for their precise mapping. Recently, two subtypes of glutamate vesicular transporters, VGLUT1 and VGLUT2, were isolated in

Acknowledgements

This research was supported by grants from Hoescht Marion Roussel and Institut National de la Santé et de la Recherche Médicale (B. Giros). E.H. was supported by a Fondation pour la Recherche Médicale (FRM) fellowship.

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