title: On the properties of identified dopaminergic neurons in the mouse substantia nigra and ventral tegmental area.
abstract: We studied the properties of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and ventral tegmental area (VTA) in mice expressing the enhanced green fluorescent protein (eGFP) under the control of the tyrosine hydroxylase promoter (TH-GFP). By using a practical map of cell positioning in distinct SNpc and VTA subregions in horizontal midbrain slices we saw that the spontaneous firing, membrane properties, cell body size and magnitude of the hyperpolarization-activated current (Ih) in TH-GFP-positive neurons (TH-GFP+) vary significantly among subregions, following a mediolateral gradient. Block of Ihwith Zd7288 inhibited firing in the most lateral subregions, but had little effect in the intermediate/medial VTA. In addition, TH-GFP+cells were excited by Met5-Enkephalin. Extracellular recordings from a large neuron number showed that all TH-GFP+cells were inhibited by dopamine, suggesting that this is a reliable approach for identifying dopaminergic neurons in vitro. Simultaneous recordings from dopamine-sensitive and dopamine-insensitive neurons showed that dopamine-insensitive cells (putative non-dopaminergic neurons) are unaffected by Zd7288 but inhibited by Met5-Enkephalin. Under patch-clamp, dopamine generated a quantitatively similar outward current in most TH-GFP+neurons, although medial VTA cells showed reduced dopamine sensitivity. Pargyline prolonged the dopamine current, whereas cocaine enhanced dopamine-mediated responses in both the SNpc and the VTA. Our work provides new insights into the variability in mouse midbrain dopaminergic neurons along the medial-lateral axis and points to the necessity of a combination of different electrophysiological and pharmacological approaches for reliably identifying these cells to distinguish them from non-dopaminergic neurons in the midbrain.
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.|Department of Systems Medicine, Faculty of Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
authors: Paraskevi
authors: P
authors: Krashia
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.|Department of Systems Medicine, Faculty of Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
authors: Alessandro
authors: A
authors: Martini
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.|Department of Medicine, University Campus-Biomedico, Rome, Italy.
authors: Annalisa
authors: A
authors: Nobili
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.|Department of Systems Medicine, Faculty of Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
authors: Daniela
authors: D
authors: Aversa
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.|Department of Medicine, University Campus-Biomedico, Rome, Italy.
authors: Marcello
authors: M
authors: D'Amelio
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.
authors: Nicola
authors: N
authors: Berretta
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.|Department of Motor Science and Wellness, University of Naples Parthenope, Naples, Italy.
authors: Ezia
authors: E
authors: Guatteo
authors: Department of Experimental Neurology, IRCCS Santa Lucia Foundation, Via del Fosso di Fiorano 64, 00143, Rome, Italy.|Department of Systems Medicine, Faculty of Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
authors: Nicola Biagio
authors: NB
authors: Mercuri
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism*; D059290:Dopaminergic Neurons / Q000378:metabolism*; D005260:Female; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008636:Mesencephalon / Q000378:metabolism; D051379:Mice; D013378:Substantia Nigra / Q000378:metabolism*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D017557:Ventral Tegmental Area / Q000378:metabolism*
chemical_list: D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine
keywords: Ih current; dopamine transporter; midbrain; monoamine oxidase; tyrosine hydroxylase