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Lee, Jungryun,Song, Kiyeong,Lee, Kyoobin,Hong, Joohyeon,Lee, Hyojung,Chae, Sangmi,Cheong, Eunji,Shin, Hee-Sup National Academy of Sciences 2013 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.110 No.50
<P>T-type Ca<SUP>2+</SUP> channels in thalamocortical (TC) neurons have long been considered to play a critical role in the genesis of sleep spindles, one of several TC oscillations. A classical model for TC oscillations states that reciprocal interaction between synaptically connected GABAergic thalamic reticular nucleus (TRN) neurons and glutamatergic TC neurons generates oscillations through T-type channel-mediated low-threshold burst firings of neurons in the two nuclei. These oscillations are then transmitted from TC neurons to cortical neurons, contributing to the network of TC oscillations. Unexpectedly, however, we found that both WT and KO mice for <I>Ca<SUB>V</SUB>3.1</I>, the gene for T-type Ca<SUP>2+</SUP> channels in TC neurons, exhibit typical waxing-and-waning sleep spindle waves at a similar occurrence and with similar amplitudes and episode durations during non-rapid eye movement sleep. Single-unit recording in parallel with electroencephalography in vivo confirmed a complete lack of burst firing in the mutant TC neurons. Of particular interest, the tonic spike frequency in TC neurons was significantly increased during spindle periods compared with nonspindle periods in both genotypes. In contrast, no significant change in burst firing frequency between spindle and nonspindle periods was noted in the WT mice. Furthermore, spindle-like oscillations were readily generated within intrathalamic circuits composed solely of TRN and TC neurons in vitro in both the KO mutant and WT mice. Our findings call into question the essential role of low-threshold burst firings in TC neurons and suggest that tonic firing is important for the generation and propagation of spindle oscillations in the TC circuit.</P>
이동수,Lim Hocheol,Lee Jungryun,하고은,No Kyoung Tai,정은지 한국뇌신경과학회 2023 Experimental Neurobiology Vol.32 No.3
Anoctamin 2 (ANO2 or TMEM16B), a calcium-activated chloride channel (CaCC), performs diverse roles in neurons throughout the central nervous system. In hippocampal neurons, ANO2 narrows action potential width and reduces postsynaptic depolarization with high sensitivity to Ca2+ at relatively fast kinetics. In other brain regions, including the thalamus, ANO2 mediates activity-dependent spike frequency adaptations with low sensitivity to Ca2+ at relatively slow kinetics. How this same channel can respond to a wide range of Ca2+ levels remains unclear. We hypothesized that splice variants of ANO2 may contribute to its distinct Ca2+ sensitivity, and thus its diverse neuronal functions. We identified two ANO2 isoforms expressed in mouse brains and examined their electrophysiological properties: isoform 1 (encoded by splice variants with exons 1a, 2, 4, and 14) was expressed in the hippocampus, while isoform 2 (encoded by splice variants with exons 1a, 2, and 4) was broadly expressed throughout the brain, including in the cortex and thalamus, and had a slower calcium-dependent activation current than isoform 1. Computational modeling revealed that the secondary structure of the first intracellular loop of isoform 1 forms an entrance cavity to the calcium-binding site from the cytosol that is relatively larger than that in isoform 2. This difference provides structural evidence that isoform 2 is involved in accommodating spike frequency, while isoform 1 is involved in shaping the duration of an action potential and decreasing postsynaptic depolarization. Our study highlights the roles and molecular mechanisms of specific ANO2 splice variants in modulating neuronal functions.
Performance Evaluation of Vehicle-mounted Mobile Relay in Next Generation Cellular Networks
( Keunhang Heo ),( Hyunsik Kang ),( Un-chul Moon ),( Jungryun Lee ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.5
Compared to nomadic and fixed relay stations, vehicle-mounted mobile relay stations show different characteristics caused by the time-variant topology, due to their mobility. Especially, a relay mounted in a vehicle is differentiated from nomadic or fixed relay by the restricted distance between the relay and associated mobile station and the variable density of relay deployment in a cell. In this paper, we identify the characteristics of vehicle-mounted mobile relay stations and provide some parameters that highly influence the performance of vehicle-mounted relay. Through simulation, we measure the effect of relay density, zone ratio, relay transmission power, and frame transmission mode on the performance of vehicle-mounted relay. The results show that the performance of vehicle-mounted relay is highly susceptible to the above vehicle-mounted relay-specific parameters.
Shim, Hyun-Ji,Jung, Won Beom,Schlegel, Felix,Lee, Joonsung,Kim, Sangwoo,Lee, Jungryun,Kim, Seong-Gi Elsevier 2018 NeuroImage Vol.177 No.-
<P><B>Abstract</B></P> <P>Mouse fMRI is critically useful to investigate functions of mouse models. Until now, the somatosensory-evoked responses in anesthetized mice are often widespread and inconsistent across reports. Here, we adopted a ketamine and xylazine mixture for mouse fMRI, which is relatively new anesthetics in fMRI experiments. Forepaw stimulation frequency was optimized using cerebral blood volume (CBV)-weighted optical imaging (n = 11) and blood-oxygenation-level dependent (BOLD) fMRI with a gradient-echo time of 16 ms at 9.4 T, and 4 Hz stimulation with 0.5 ms and 0.5 mA pulses induced the highest hemodynamic response. For 20-s 4-Hz unilateral forepaw stimulation, localized BOLD activity was consistently found in the contralateral primary forelimb somatosensory cortex (S1FL), while no significant change was observed in the ipsilateral S1FL. The mean magnitude was 1.44 ± 0.20% SEM (n = 9) in the contralateral S1FL and 0.69 ± 0.10% in the contralateral thalamus. The variability of evoked fMRI responses across sessions was investigated by comparing with resting state fMRI (rsfMRI) functional connectivity (FC). Evoked responses in S1FL were correlated positively with rsfMRI FC between bilateral S1FL (r = 0.63 to 0.69) and negatively with FC between S1FL and the anterior cingulate cortex (r = −0.50 to −0.57), suggesting that rsfMRI FC is a good index of the evoked fMRI response and anesthetized animal condition. Finally, three weekly fMRI scans were performed in 5 mice, and localized activity was reproducibly observed in S1FL, with a success rate of 70–95%. In summary, our developed fMRI protocol can be used for mapping functions of mouse models.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bilateral BOLD response induced by forepaw stimulation is observed under isoflurane. </LI> <LI> Ketamine and xylazine anesthesia is used for mouse fMRI. </LI> <LI> Forepaw stimulation of 4 Hz evokes the highest hemodynamic response. </LI> <LI> BOLD activation is reproducibly localized at the contralateral somatosensory cortex. </LI> <LI> Resting-state functional connectivity predicts evoked fMRI responses. </LI> </UL> </P>