Berglund Ken

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Berglund
First Name
Ken
ORCID
0000-0003-4341-0838

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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
    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.