title: Imaging synaptic inhibition in transgenic mice expressing the chloride indicator, Clomeleon.
abstract: We describe here a molecular genetic approach for imaging synaptic inhibition. The thy-1 promoter was used to express high levels of Clomeleon, a ratiometric fluorescent indicator for chloride ions, in discrete populations of neurons in the brains of transgenic mice. Clomeleon was functional after chronic expression and provided non-invasive readouts of intracellular chloride concentration ([Cl(-)](i)) in brain slices, allowing us to quantify age-dependent declines in resting [Cl(-)](i) during neuronal development. Activation of hippocampal interneurons caused [Cl(-)](i) to rise transiently in individual postsynaptic pyramidal neurons. [Cl(-)](i) increased in direct proportion to the amount of inhibitory transmission, with peak changes as large as 4 mM. Integrating responses over populations of pyramidal neurons allowed sensitive detection of synaptic inhibition. Thus, Clomeleon imaging permits non-invasive, spatiotemporally resolved recordings of [Cl(-)](i) in a large variety of neurons, opening up new opportunities for imaging synaptic inhibition and other forms of chloride signaling.
authors.affiliation: Department of Neurobiology, Duke Univ. Medical Center, Box 3209, Durham, NC 27710, USA.
authors.forename: Ken
authors.initials: K
authors.lastname: Berglund
authors.forename: Wolfram
authors.initials: W
authors.lastname: Schleich
authors.forename: Patrik
authors.initials: P
authors.lastname: Krieger
authors.forename: Li Shen
authors.initials: LS
authors.lastname: Loo
authors.forename: Dongqing
authors.initials: D
authors.lastname: Wang
authors.forename: Nell B
authors.initials: NB
authors.lastname: Cant
authors.forename: Guoping
authors.initials: G
authors.lastname: Feng
authors.forename: George J
authors.initials: GJ
authors.lastname: Augustine
authors.forename: Thomas
authors.initials: T
authors.lastname: Kuner
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism / Q000648:ultrastructure; D002712:Chlorides / Q000032:analysis* / Q000378:metabolism; D004558:Electric Stimulation; D007202:Indicators and Reagents; D007395:Interneurons / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000378:metabolism; D009448:Neurochemistry / Q000379:methods*; D009482:Neurophysiology / Q000379:methods*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods*; D013569:Synapses / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology
chemical_list: D002712:Chlorides; D007202:Indicators and Reagents; D011993:Recombinant Fusion Proteins; C415371:clomeleon