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

Abstract

GABA neurons in the VTA and SNc play key roles in reward and aversion through their local inhibitory control of dopamine neuron activity and through long-range projections to several target regions including the nucleus accumbens. It is not clear whether some of these GABA neurons are dedicated local interneurons or if they all collateralize and send projections externally as well as making local synaptic connections. Testing between these possibilities has been challenging in the absence of interneuron-specific molecular markers. We hypothesized that one potential candidate might be neuronal nitric oxide synthase (nNOS), a common interneuronal marker in other brain regions. To test this, we used a combination of immunolabelling (including antibodies for nNOS that we validated in tissue from nNOS-deficient mice) and cell type-specific virus-based anterograde tracing in mice. We found that nNOS-expressing neurons, in the parabrachial pigmented (PBP) part of the VTA and the SNc were GABAergic and did not make detectable projections, suggesting they may be interneurons. In contrast, nNOS-expressing neurons in the rostral linear nucleus (RLi) were mostly glutamatergic and projected to a number of regions, including the lateral hypothalamus (LH), the ventral pallidum (VP), and the median raphe (MnR) nucleus. Taken together, these findings indicate that nNOS is expressed by neurochemically- and anatomically-distinct neuronal sub-groups in a sub-region-specific manner in the VTA and SNc.

Regulatory system of mGluR group II in the nucleus accumbens for methamphetamine‐induced dopamine increase by the medial prefrontal cortex

“…For this purpose, we performed DARPP‐32 and nNOS (neuronal nitric oxide synthase) immunohistochemistry in VTA (Figure B,C). nNOS is expressed in a subset of interneurons in the VTA . Interestingly, we found some colocalization of DARPP‐32 and nNOS in VTA as indicated by the white arrowheads (Figure C).…”

“…nNOS is expressed in a subset of interneurons in the VTA. 17 Interestingly, we found some colocalization of DARPP-32 and nNOS in VTA as indicated by the white arrowheads ( Figure 3C).…”

“…Remarkably, a study showed that neuronal nitric oxide synthase (nNOS) is also another marker of interneurons in VTA. nNOS was identified as a marker of VTA GABA interneurons that is not expressed in VTA DA neurons, and putatively expressed in glutamatergic projecting neurons, mostly in the rostral linear nucleus of the raphe (RLi) . Although, glutamatergic neurons represent only 2%‐3% of total VTA neurons .…”

“…nNOS was identified as a marker of VTA GABA interneurons that is not expressed in VTA DA neurons, and putatively expressed in glutamatergic projecting neurons, mostly in the rostral linear nucleus of the raphe (RLi). 17 Although, glutamatergic neurons represent only 2%-3% of total VTA neurons. 33 We performed immunohistochemistry of nNOS and DARPP-32 and detected a colocalization of DARPP-32 and nNOS ( Figure 3C).…”

Dysfunction of ventral tegmental area GABA neurons causes mania-like behavior

“…For this paper, we focus on the midline VTA, which contains GABA (VTA Vgat ) and glutamate/nitric oxide synthase (VTA Vglut2 ) neurons [25,28,[34][35][36][37]. These VTA Vgat and VTA Vglut2/NOS1 neurons inhibit and excite, respectively, the dopamine cells, but also, by projecting out of the VTA, exert effects independent of dopamine [25,28,36].…”