Ventral tegmental area dopamine and GABA neurons: Physiological properties and expression of mRNA for endocannabinoid biosynthetic elements

Abstract

The ventral tegmental area (VTA) is involved in adaptive reward and motivation processing and is composed of dopamine (DA) and GABA neurons. Defining the elements regulating activity and synaptic plasticity of these cells is critical to understanding mechanisms of reward and addiction. While endocannabinoids (eCBs) that potentially contribute to addiction are known to be involved in synaptic plasticity mechanisms in the VTA, where they are produced is poorly understood. In this study, DA and GABAergic cells were identified using electrophysiology, cellular markers, and a transgenic mouse model that specifically labels GABA cells. Using single-cell RT-qPCR and immunohistochemistry, we investigated mRNA and proteins involved in eCB signaling such as diacylglycerol lipase α, N-acyl-phosphatidylethanolamine-specific phospholipase D, and 12-lipoxygenase, as well as type I metabotropic glutamate receptors (mGluRs). Our results demonstrate the first molecular evidence of colocalization of eCB biosynthetic enzyme and type I mGluR mRNA in VTA neurons. Further, these data reveal higher expression of mGluR1 in DA neurons, suggesting potential differences in eCB synthesis between DA and GABA neurons. These data collectively suggest that VTA GABAergic and DAergic cells have the potential to produce various eCBs implicated in altering neuronal activity or plasticity in adaptive motivational reward or addiction.

Voluntary adolescent drinking enhances excitation by low levels of alcohol in a subset of dopaminergic neurons in the ventral tegmental area

“…It has become clear that the physiological criteria that were formerly used to identify dopaminergic neurons within the VTA are in fact somewhat misleading, as these “classical” criteria have been shown to not only exclude some DAergic neurons but also to include non-DA neurons (Margolis et al, 2006, 2008b; Lammel et al, 2008; Merrill et al, 2015; but see Chieng et al, 2011). To aid in the identification of DA neurons, most of our experiments were performed in TH-GFP mice (Sawamoto et al, 2001), providing us with an alternate means to identify a population of medial VTA DA neurons that have previously been under-studied (Lammel et al, 2008).…”

Persistent seizure control in epileptic mice transplanted with gamma‐aminobutyric acid progenitors

“…3E). Although most GFP-positive neurons co-labeled with an antibody to the GABA synthesizing enzyme GAD67 these cell counts may underestimate the true number of MGE-derived GABAergic interneurons because (i) tissue for these studies was processed from adult mice undergoing various procedures that could impact activity-dependent enzyme levels, and (ii) GAD67 expression was confirmed in only 75% of GFP-expressing cells in studies using GAD67-GFP mice 51 . It has previously been shown that IPSC frequency, a physiological measure of GABA-mediated inhibition, is enhanced 20-40% in regions containing MGE progenitor derived interneurons 11,15,17,38 .…”

nNOS-Expressing Neurons in the Ventral Tegmental Area and Substantia Nigra Pars Compacta

“…Testing between these possibilities has been challenging in the absence of interneuron-specific molecular markers. Indeed, of the cardinal interneuron markers used to identify and selectively target sub-populations of interneurons in other regions of the brain, most are either not expressed in either the VTA or SNc, or are also expressed by sub-groups of dopamine neurons (e.g., somatostatin, cholecystokinin, vasoactive intestinal peptide, neuropeptide Y, parvalbumin, and calretinin; Hökfelt et al, 1980; Seroogy et al, 1988 , 1989; Rogers, 1992; Isaacs and Jacobowitz, 1994; Liang et al, 1996; Gonzalez-Hernandez and Rodriguez, 2000; Klink et al, 2001; Lein et al, 2007; Olson and Nestler, 2007; Dougalis et al, 2012; Merrill et al, 2015 ). One potential candidate, however, is neuronal nitric oxide synthase (nNOS).…”