title: Electrical and Ca(2+) signaling in dendritic spines of substantia nigra dopaminergic neurons.
abstract: Little is known about the density and function of dendritic spines on midbrain dopamine neurons, or the relative contribution of spine and shaft synapses to excitability. Using Ca(2+) imaging, glutamate uncaging, fluorescence recovery after photobleaching and transgenic mice expressing labeled PSD-95, we comparatively analyzed electrical and Ca(2+) signaling in spines and shaft synapses of dopamine neurons. Dendritic spines were present on dopaminergic neurons at low densities in live and fixed tissue. Uncaging-evoked potential amplitudes correlated inversely with spine length but positively with the presence of PSD-95. Spine Ca(2+) signals were less sensitive to hyperpolarization than shaft synapses, suggesting amplification of spine head voltages. Lastly, activating spines during pacemaking, we observed an unexpected enhancement of spine Ca(2+) midway throughout the spike cycle, likely involving recruitment of NMDA receptors and voltage-gated conductances. These results demonstrate functionality of spines in dopamine neurons and reveal a novel modulation of spine Ca(2+) signaling during pacemaking.
authors.affiliation: Cellular Neurophysiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States.
authors.forename: Travis A
authors.initials: TA
authors.lastname: Hage
authors.affiliation: Cellular Neurophysiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Cellular Neurophysiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States.
authors.forename: Zayd M
authors.identifier: 0000-0002-1445-1457
authors.initials: ZM
authors.lastname: Khaliq
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism; D003584:Cytological Techniques; D049229:Dendritic Spines / Q000502:physiology*; D059290:Dopaminergic Neurons / Q000502:physiology*; D055724:Electrophysiological Phenomena; D051379:Mice; D008822:Mice, Transgenic; D015398:Signal Transduction; D013378:Substantia Nigra / Q000502:physiology*; D013569:Synapses / Q000502:physiology*
chemical_list: D002413:Cations, Divalent; D002118:Calcium
keywords: dendrites; dopaminergic; imaging; mouse; neuroscience; spines; synapse