Biology subjects

Melani, R.

Publications and source records attributed to Melani, R..

5 recordsLinked to original sources

bioRxiv2026

Distinct forms of dopamine transmission control locomotion and learning

The neuromodulator dopamine is essential for voluntary movement and learning from experience. While these behaviors often occur simultaneously and rely on overlapping nigrostriatal dopamine circuits, they are also separable and can manifest independently. How a single neuromodulatory system controls such disparate aspects of behavior in parallel remains poorly understood. Here we show that striatal dopamine is released through two spatially and functionally distinct modes that are independently regulated and serve distinct behavioral roles. Eliminating dopamine release underlying bulk extracellular accumulation reveals a spatially restricted mode of transmission that maintains phasic dopamine receptor activation on striatal projection neurons. We find that selective loss of diffuse dopamine impairs striatal circuit excitability and reduces locomotion, while point-to-point transmission is sufficient to maintain striatal spine density and support motor and associative learning. We propose that the geometry of dopamine release determines its behavioral output, a principle that explains the breadth of dopamines functions and more broadly elucidates how neurons multiplex different forms of information.

neuroscience↗

bioRxiv2026

Defining state-selective lipid binding to brain GPCRs - introducing REVEAL

Membrane lipids are central regulators of G protein-coupled receptor (GPCR) function. Defining receptor-specific lipid interactions in native, fully modified mammalian systems remains challenging. Extensive post-translational modifications generate heterogeneous proteoforms that confound conventional mass spectrometry approaches. Here we introduce REVEAL (REceptor enVironment Elucidation by Activated Lipid-release), an automated native top-down mass spectrometry strategy that discriminates specifically bound lipids from background. Applied here to intact, heterogeneous mammalian membrane protein complexes, incubated with a brain polar lipid extract (>1000 components), we define receptor-specific lipid-binding for two neuronal class C GPCRs. We show that agonism remodels lipid occupancy, selectively enriching a reduced repertoire of bound lipids. Plasmalogen lipids emerge as persistent binders across all conformational states of the metabotropic glycine receptor and are preferentially depleted under oxidative stress, implying a protective role at the receptor surface. These findings position lipids as dynamic regulators of both function and response to the cellular redox environment.

biophysics↗

bioRxiv2023

Comment on 'Accumbens cholinergic interneurons dynamically promote dopamine release and enable motivation'

Acetylcholine is widely believed to modulate the release of dopamine in the striatum of mammals. Experiments in brain slices clearly show that synchronous activation of striatal cholinergic interneurons is sufficient to drive dopamine release via axo-axonal stimulation of nicotinic acetylcholine receptors. However, evidence for this mechanism in vivo has been less forthcoming. A recent paper in eLife (Mohebi et al., 2023) reported that, in awake behaving rats, optogenetic activation of striatal cholinergic interneurons with blue light readily evokes dopamine release measured with the red fluorescent sensor RdLight1. Here, we show that blue light alone alters the fluorescent properties of RdLight1 in a manner that may be misconstrued as phasic dopamine release, and that this artefactual photoactivation can account for the effects attributed to cholinergic interneurons. Our findings indicate that measurements of dopamine using the red-shifted fluorescent sensor RdLight1 should be interpreted with caution when combined with optogenetics. In light of this and other publications that did not observe large acetylcholine-evoked dopamine transients in vivo, the conditions under which such release occurs in behaving animals remain unknown.

neuroscience↗

bioRxiv2022

A permissive role for dopamine in the production of vigorous movements

Dopamine is essential for the production of vigorous movements, but how dopamine modifies the gain of motor commands remains unclear. Here, we developed a dexterous motor task in which head-restrained mice self-initiate fast and large-amplitude lever pushes with their left forelimb to earn rewards. We show that this task is goal-directed and depends on cortico-striatal circuits in the hemisphere contralateral to the limb used to push the lever. We find that unilateral loss of midbrain dopamine neurons reduces the speed and amplitude of lever pushes, and that levodopa treatment rapidly restores motor vigor, consistent with parkinsonian bradykinesia. Photometry recordings of striatal dopamine levels indicate that the therapeutic efficacy of levodopa does not require phasic dopamine release. In dopamine-intact mice, optogenetic stimulation of midbrain dopamine neurons calibrated to mimic transients evoked by rewards is also insufficient to increase the speed and amplitude of forelimb movements. Together, our data show that phasic dopamine transients are unlikely to specify the vigor of forelimb movements online as they are being executed, and suggest instead that dopamine plays a permissive role in the selection and production of vigorous movements. Our findings have important implications for our understanding of how the basal ganglia contribute to motor control under physiological conditions and in Parkinsons disease.

neuroscience↗

bioRxiv2021

Inhibitory co-transmission from midbrain dopamine neurons relies on presynaptic GABA uptake

Dopamine (DA)-releasing neurons in the substantia nigra pars compacta (SNcDA) inhibit target cells in the striatum through postsynaptic activation of {gamma}-aminobutyric acid (GABA) receptors. However, the molecular mechanisms responsible for GABAergic signaling remain unclear, as SNcDA neurons lack enzymes typically required to produce GABA or package it into synaptic vesicles. Here we show that aldehyde dehydrogenase 1a1 (Aldh1a1), an enzyme proposed to function as a GABA synthetic enzyme in SNcDA neurons does not produce GABA for synaptic transmission. Instead, we demonstrate that SNcDA axons obtain GABA exclusively through presynaptic uptake using the membrane GABA transporter Gat1 (encoded by Slc6a1). GABA is then packaged for vesicular release using the vesicular monoamine transporter Vmat2. Our data therefore show that presynaptic transmitter recycling can substitute for de novo GABA synthesis and that Vmat2 contributes to vesicular GABA transport, expanding the range of molecular mechanisms available to neurons to support inhibitory synaptic communication.

neuroscience↗