Feng Guoping

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Feng
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Guoping
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  • Article
    Optogenetic visualization of presynaptic tonic inhibition of cerebellar parallel fibers
    (Society for Neuroscience, 2016-05-25) Berglund, Ken ; Wen, Lei ; Dunbar, Robert L. ; Feng, Guoping ; Augustine, George J.
    Tonic inhibition was imaged in cerebellar granule cells of transgenic mice expressing the optogenetic chloride indicator, Clomeleon. Blockade of GABAA receptors substantially reduced chloride concentration in granule cells due to block of tonic inhibition. This indicates that tonic inhibition is a significant contributor to the resting chloride concentration of these cells. Tonic inhibition was observed not only in granule cell bodies, but also in their axons, the parallel fibers (PFs). This presynaptic tonic inhibition could be observed in slices both at room and physiological temperatures, as well as in vivo, and has many of the same properties as tonic inhibition measured in granule cell bodies. GABA application revealed that PFs possess at least two types of GABAA receptor: one high-affinity receptor that is activated by ambient GABA and causes a chloride influx that mediates tonic inhibition, and a second with a low affinity for GABA that causes a chloride efflux that excites PFs. Presynaptic tonic inhibition regulates glutamate release from PFs because GABAA receptor blockade enhanced both the frequency of spontaneous EPSCs and the amplitude of evoked EPSCs at the PF-Purkinje cell synapse. We conclude that tonic inhibition of PFs could play an important role in regulating information flow though cerebellar synaptic circuits. Such cross talk between phasic and tonic signaling could be a general mechanism for fine tuning of synaptic circuits.
  • Article
    Optogenetic mapping of cerebellar inhibitory circuitry reveals spatially biased coordination of interneurons via electrical synapses
    (Cell Press, 2014-05-22) Kim, Jinsook ; Lee, Soojung ; Tsuda, Sachiko ; Zhang, Xuying ; Asrican, Brent ; Gloss, Bernd ; Feng, Guoping ; Augustine, George J.
    We used high-speed optogenetic mapping technology to examine the spatial organization of local inhibitory circuits formed by cerebellar interneurons. Transgenic mice expressing channelrhodopsin-2 exclusively in molecular layer interneurons allowed us to focally photostimulate these neurons, while measuring resulting responses in postsynaptic Purkinje cells. This approach revealed that interneurons converge upon Purkinje cells over a broad area and that at least seven interneurons form functional synapses with a single Purkinje cell. The number of converging interneurons was reduced by treatment with gap junction blockers, revealing that electrical synapses between interneurons contribute substantially to the spatial convergence. Remarkably, gap junction blockers affected convergence in sagittal slices, but not in coronal slices, indicating a sagittal bias in electrical coupling between interneurons. We conclude that electrical synapse networks spatially coordinate interneurons in the cerebellum and may also serve this function in other brain regions.
  • Article
    Next-generation transgenic mice for optogenetic analysis of neural circuits
    (Frontiers Media, 2013-11-26) Asrican, Brent ; Augustine, George J. ; Berglund, Ken ; Chen, Susu ; Chow, Nick ; Deisseroth, Karl ; Feng, Guoping ; Gloss, Bernd ; Hira, Riichiro ; Hoffmann, Carolin ; Kasai, Haruo ; Katarya, Malvika ; Kim, Jinsook ; Kudolo, John ; Lee, Li Ming ; Lo, Shun Qiang ; Mancuso, James ; Matsuzaki, Masanori ; Nakajima, Ryuichi ; Qiu, Li ; Tan, Gregory ; Tang, Yanxia ; Ting, Jonathan T. ; Tsuda, Sachiko ; Wen, Lei ; Zhang, Xuying ; Zhao, Shengli
    Here we characterize several new lines of transgenic mice useful for optogenetic analysis of brain circuit function. These mice express optogenetic probes, such as enhanced halorhodopsin or several different versions of channelrhodopsins, behind various neuron-specific promoters. These mice permit photoinhibition or photostimulation both in vitro and in vivo. Our results also reveal the important influence of fluorescent tags on optogenetic probe expression and function in transgenic mice.