Particular subpopulations of midbrain and hypothalamic dopamine neurons express vesicular glutamate transporter 2 in the rat brain

Abstract

Vesicular glutamate transporters (VGLUT1, ‐2, and ‐3) mediate the accumulation of transmitter glutamate into synaptic vesicles in glutamatergic neurons. VGLUT1 and VGLUT2 are more reliable glutamatergic neuron markers, since VGLUT3 also exists in other neuron types. To study whether the dopaminergic neuron uses glutamate as a cotransmitter, we analyzed VGLUTs expression in dopamine neurons of adult male rats by in situ hybridization and immunohistochemistry. In the ventral midbrain, in situ hybridization analysis revealed no VGLUT1 mRNA expression, a widespread but discrete pattern of VGLUT2 mRNA expression, and a highly limited expression of VGLUT3 mRNA. Reverse‐transcriptase polymerase chain reaction analysis detected full‐length VGLUT2 gene transcripts in the ventral midbrain. Using in situ hybridization combined with tyrosine hydroxylase (TH) immunostaining, only VGLUT2 signals were detectable in some TH‐labeled neurons of A10 dopamine neuron groups, with the highest incidence (20%) in the rostral linear nucleus of the ventral tegmental area. In the forebrain, VGLUT2 signals were demonstrated in half of the A11 TH‐labeled neurons in the hypothalamus. Double‐label immunostaining for VGLUT2 and vesicular monoamine transporter 2 or TH showed that double‐labeled varicosities are rarely observed in any target regions examined of A10 and A11 dopamine neuron groups. These results indicate that VGLUT2 is expressed in subsets of A10 and A11 dopamine neurons, which might release dopamine and glutamate separately from different varicosities in the majority of their single axons. J. Comp. Neurol. 498:581–592, 2006. © 2006 Wiley‐Liss, Inc.

Developmental and Target-Dependent Regulation of Vesicular Glutamate Transporter Expression by Dopamine Neurons

“…In line with previous reports (Dal Bo et al, 2004;Hur and Zaborszky, 2005;Kawano et al, 2006;Yamaguchi et al, 2007), using single-cell RT-PCR we detected a subpopulation of purely glutamatergic (i.e., not expressing TH) neurons in the VTA/SN region. We detected them in freshly dissociated neurons at P0 as well as in acute VTA/SN horizontal brain slices prepared from P14 TH-GFP and VGluT2-EGFP mice (supplemental Fig.…”

“…However, the expression of VGluTs in DA neurons in vivo has remained controversial. Whereas initial in situ hybridization studies failed to detect VGluT transcripts in the ventral mesencephalon (Fremeau et al, 2001;Gras et al, 2002;Schafer et al, 2002;Herzog et al, 2004) (but see Fremeau et al, 2002), a recent in situ hybridization study, Kawano et al (2006) showed that VGluT2 mRNA is found in a small subset of DA neurons of the medial nuclei of the A10 cell group in adult rats. Another similar study reported only very few DA neurons coexpressing VGluT2 in the adult VTA (Yamaguchi et al, 2007).…”

“…In relative contradiction, the majority of mesencephalic DA neurons in microculture selectively express VGluT2 (Dal Bo et al, 2004). Finally, in a recent in situ hybridization study performed in adult rats, expression of VGluT2 was reported in a subset of DA neurons of the rostral linear (RLi), interfascicular (IF), and caudal linear nuclei (CLi) (Kawano et al, 2006), cell groups that, with the VTA, are components of the A10 catecholaminergic neurons. In a similar study, DA neurons coexpressing VGluT2 mRNA were reported to be very rare (ϳ0.1%) in the VTA of adult rats (Yamaguchi et al, 2007).…”

VGLUT2 in dopamine neurons is required for psychostimulant-induced behavioral activation

“…During the past few years, with the identification of the vesicular glutamate transporters (3)(4)(5)28), it has been possible to analyze the vesicular glutamate packaging properties of the mDA neurons. Several groups, including ours, have shown that a subset of mDA neurons expresses Vglut2 mRNA, a finding that makes the use of glutamate as a neurotransmitter a possibility in these neurons (14,29,30). Kawano et al (29) showed that the area containing the most Vglut2-and TH-expressing neurons was the RLi, with somewhat lower expression in the interfascicular nucleus, the rostral part of the caudal linear nucleus, the parabrachial pigmented nucleus, and the paranigral nucleus of the VTA.…”

Enhanced Sucrose and Cocaine Self-Administration and Cue-Induced Drug Seeking after Loss of VGLUT2 in Midbrain Dopamine Neurons in Mice

“…Studies examining the expression of Vglut2 in midbrain DA neurons have shown this cophenotype to be present in both the SNc and VTA from early development to adult stages (Dal Bo et al, 2004;Mendez et al, 2008;Birgner et al, 2010). However, it has been emphasized that the cophenotype is more abundant in VTA than SNc neurons, at least in the postnatal rat (Dal Bo et al, 2004Kawano et al, 2006;Mendez et al, 2008;Yamaguchi et al, 2011). Moreover, whereas VGLUT2 protein has been detected in DA axon terminals (tyrosine hydroxylase-positive) of both the NAc and DStr in the preadolescent rat, it could no longer be observed in the adult (Bérubé-Carrière et al, 2009;Moss et al, 2011).…”