Inhibitory Effects of EGCG on the Dopaminergic Neurons

Tag-Heo,Sujeong Jang,Song-Hee Kim,Han-Seong Jeong,Jong-Seong Park 대한의생명과학회 2009 Biomedical Science Letters Vol.15 No.2

This study was designed to investigate the effects of high concentration of (-)-epigallocatechin-3-gallate (EGCG) on the neuronal activity of rat substantia nigra dopaminergic neurons. Sprague-Dawley rats aged 14 to 16 days were decapitated under ether anesthesia. After treatment with pronase and thermolysin, the dissociated dopaminergic neurons were transferred into a chamber on an inverted microscope. Spontaneous action potentials and potassium currents were recorded by standard patch-clamp techniques under current and voltage-clamp modes respectively. 18 dopaminergic neurons (80%) revealed inhibitory responses to 40 and 100 μM of EGCG and 4 neurons (20%) did not respond to EGCG. The spike frequency and resting membrane potential of these cells were decreased by EGCG. The amplitude of afterhyperpolarization was increased by EGCG. Whole potassium currents of dopaminergic neurons were increased by EGCG (n=10). These experimental results suggest that high concentration EGCG decreases the neuronal activity of the dopaminergic neurons by altering the resting membrane potential and afterhyperpolarization.

Effects of Sphingosine-1-phosphate on Vestibular Nuclear Neurons

Jae-Hyuk Lee,Sujeong Jang,Song-Hee Kim,Han-Seong Jeong,Jong-Seong Park(박종성) 대한의생명과학회 2010 Biomedical Science Letters Vol.16 No.1

This study was designed to investigate the effects of sphingosine-1-phosphate on the neuronal activity of rat medial vestibular nuclear neurons. Sprague-Dawley rats aged 14 to 16 days were decapitated under ether anesthesia. After treatment with pronase and thermolysin, the dissociated medial vestibular nuclear neurons were transferred into a chamber on an inverted microscope. Spontaneous action potentials and potassium currents were recorded by standard patch-clamp techniques under current and voltage-clamp modes respectively. 15 medial vestibular nuclear neurons revealed excitatory responses to 1 and 5 μM of sphingosine-1-phosphate. The spike frequency and resting membrane potential of these cells were increased by sphingosine-1-phosphate. The amplitude of afterhyperpolarization was decreased by sphingosine-1-phosphate. Whole potassium currents of medial vestibular nuclear neurons were decreased by sphingosine-1-phosphate (n=12). Sphingosine-1-phosphate did not affect the charybdotoxin-treated potassium currents. These experimental results suggest that sphingosine-1-phosphate increases the neuronal activity of the medial vestibular nuclear neurons by altering the resting membrane potential and afterhyperpolarization.

Calcium-activated chloride channels: a new target to control the spiking pattern of neurons

( Go Eun Ha ),( Eunji Cheong ) 생화학분자생물학회(구 한국생화학분자생물학회) 2017 BMB Reports Vol.50 No.3

The nature of encoded information in neural circuits is determined by neuronal firing patterns and frequencies. This paper discusses the molecular identity and cellular mecha-nisms of spike-frequency adaptation in the central nervous system (CNS). Spike-frequency adaptation in thalamocortical (TC) and CA1 hippocampal neurons is mediated by the Ca²⁺-activated Cl^- channel (CACC) anoctamin-2 (ANO2). Knockdown of ANO2 in these neurons results in increased number of spikes, in conjunction with significantly reduced spike-frequency adaptation. No study has so far demonstrated that CACCs mediate afterhyperpolarization currents, which result in the modulation of neuronal spike patterns in the CNS. Our study therefore proposes a novel role for ANO2 in spike-frequency adaptation and transmission of information in the brain. [BMB Reports 2017; 50(3): 109-110]

Spike Frequency Adaptation in Neurons of the Central Nervous System

Ha, Go Eun,Cheong, Eunji The Korean Society for Brain and Neural Science 2017 Experimental Neurobiology Vol.26 No.4

<P>Neuronal firing patterns and frequencies determine the nature of encoded information of the neurons. Here we discuss the molecular identity and cellular mechanisms of spike-frequency adaptation in central nervous system (CNS) neurons. Calcium-activated potassium (K<SUB>Ca</SUB>) channels such as BK<SUB>Ca</SUB> and SK<SUB>Ca</SUB> channels have long been known to be important mediators of spike adaptation via generation of a large afterhyperpolarization when neurons are hyper-activated. However, it has been shown that a strong hyperpolarization via these K<SUB>Ca</SUB> channels would cease action potential generation rather than reducing the frequency of spike generation. In some types of neurons, the strong hyperpolarization is followed by oscillatory activity in these neurons. Recently, spike-frequency adaptation in thalamocortical (TC) and CA1 hippocampal neurons is shown to be mediated by the Ca<SUP>2+</SUP>-activated Cl- channel (CACC), anoctamin-2 (ANO2). Knockdown of ANO2 in these neurons results in significantly reduced spike-frequency adaptation accompanied by increased number of spikes without shifting the firing mode, which suggests that ANO2 mediates a genuine form of spike adaptation, finely tuning the frequency of spikes in these neurons. Based on the finding of a broad expression of this new class of CACC in the brain, it can be proposed that the ANO2-mediated spike-frequency adaptation may be a general mechanism to control information transmission in the CNS neurons.</P>

전정 유모세포 통합 모델을 이용한 반강성 기전 기반 섬모번들 특성 추정에 관한 연구

김동영,홍기환,김규성,이상민,Kim, Dongyoung,Hong, Kihwan,Kim, Kyu-Sung,Lee, Sangmin 대한의용생체공학회 2013 의공학회지 Vol.34 No.4

In this paper hair bundle feature model and integration method for hair cell models were proposed. The proposed hair bundle feature model was based on spring-damper-mass model. Input of integrated vestibular hair cell model was frequency and output was interspike interval of hair cell that was reflected the feature of hair bundles. Irregular afferents that had a great gain variation showed reduction of negative stiffness section. Regular afferents that had a small gain variation, however, showed same feature with base negative stiffness feature. As a result, integrated vestibular hair cell model showed almost the same modeling data with experimental data in the modeled eleven frequency bands. It is verified that the proposed model is a good model for hair bundle feature modeling.

반강성 특성이 반영된 전정 유모세포 모델의 활동전위 생성에 관한 연구

김동영(Dongyoung Kim),홍기환(Kihwan Hong),김규성(Kyu-Sung Kim),이상민(Sangmin Lee) 대한전자공학회 2014 전자공학회논문지 Vol.51 No.9

본 논문에서는 섬모 번들 특성 모델과 통합 전정 유모세포 모델을 제안한다. 기존 전정기관 모델에 관한 연구는 외력이 없는 상태에서 전정 유모세포의 섬모 번들이 가지는 특성이나 시냅스에서 발생하는 활동전위만을 대상으로 진행되었으며 섬모번들의 고유 특성을 고려한 전정신경의 활동전위에 대한 연구는 이루어지지 않았다. 제안된 통합 전정 유모세포 모델은 외력을 반영하였고 서로 다른 규칙성을 가진 유모세포에 대해 각각의 섬모번들의 반강성 특성을 고려하였고 이를 기존의 외력없는 모델과 비교하였다. 그 결과 외부 자극의 변화에 따른 주파수 변화가 큰 불규칙적 신경섬유와 중간규칙적 신경섬유에서는 반강성 구간의 감소를 보였으나 그렇지 않은 규칙적 신경섬유에서는 기존의 반강성 특성과 유사한 특성을 보여주었다. 또한 제안된 전정 유모세포 모델을 통해 11개의 주파수 대역에서의 모델링 데이터와 기존의 동물 실험 데이터가 거의 일치함을 보여주었다. 제안된 섬모 번들 특성 모델이 적절히 모델링되었음이 확인된다. In this paper, the vestibular hair bundle feature model and integrated vestibular hair cell model were proposed. In conventional modeling studies of vestibular system, only partial mechanisms were modeled, such as the characteristics of the vestibular hair bundles without external forces or the action potential of synapse, and the study about action potential of vestibular afferent considering the characteristics of the vestibular hair bundle was not performed. The proposed integrated vestibular hair cell model reflects external forces considering negative stiffness features of each hair bundles with different regularities of hair cells and our model was compared with conventional model without external forces. As a result, irregular afferent and intermediate afferent with high ratio of firing frequency variations to the changes of external stimulation had small width of negative stiffness section, but the width of the negative stiffness of regular afferent with low ratio was similar to that of conventional negative stiffness features. And the proposed integrated vestibular hair cell model showed almost same results with conventional data with animal experiments in 11 chosen frequency bands. It is verified that our proposed hair bundle feature model is adequately modeled.