• The Korean Journal of Physiology and Pharmacology
• /
• 제7권6호
• /
• pp.317-323
• /
• 2003

Interneuron diversity is one of the key factors to hinder understanding the mechanism of cortical neural network functions even with their important roles. We characterized inhibitory interneurons in layer II/III of the rat primary visual cortex, using patch-clamp recording and confocal reconstruction, and classified inhibitory interneurons into fast spiking (FS), late spiking (LS), burst spiking (BS), and regular spiking non-pyramidal (RSNP) neurons according to their electrophysiological characteristics. Global parameters to identify inhibitory interneurons were resting membrane potential (＞-70 mV) and action potential (AP) width (＜0.9 msec at half amplitude). FS could be differentiated from LS, based on smaller amplitude of the AP (＜∼50 mV) and shorter peak-to-trough time (P-T time) of the afterhyperpolarization (＜4 msec). In addition to the shorter AP width, RSNP had the higher input resistance (＞200 $M{Omega}$) and the shorter P-T time (＜20 msec) than those of regular spiking pyramidal neurons. Confocal reconstruction of recorded cells revealed characteristic morphology of each subtype of inhibitory interneurons. Thus, our results provide at least four subtypes of inhibitory interneurons in layer II/III of the rat primary visual cortex and a classification scheme of inhibitory interneurons.

• 대한소아치과학회지
• /
• 제25권4호
• /
• pp.671-682
• /
• 1998

Electrophysiological phenomena of pyramidal cells in the CA1 area of the dorsal hippocampus were recorded from and filled with neurobiotin in anesthetized rats. The electropharmacological properties of membrane as well as the cellular-synaptic generation of rhythmic slow activity (theta) were examined. The intracellular response characteristics of these pyramidal cells were distinctly different from responses of interneurons. Pyramidal cells had a high resting membrane potential, a low input resistance, and a large amplitude action potential. A afterhyperpolarization was followed a single action potential. Most of pyramidal cells did not display a spontaneous firing. Pyramidal cells displayed weak inward rectification and anodal break excitation. The slope of the frequency-current relation was 53.4 Hz/nA for the first interspike interval and 15.9 Hz/nA for the last intervals, suggesting the presence of spike frequency adaptation. Neurobiotin-filled neurons showed pyramidal morphology. Cells were generally bipolar dendritc processes ramifying in stratum lacunosum-moleculare, radiatum, and oriens. Commissural stimulation discharged pyramidal cells, followed by excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs). The frequency of theta-related membrane potential oscillation was voltage-independent in pyramidal neurons. At strong depolarization levels (less than 30 mV) pyramidal cells emitted sodium spike oscillation, phase-locked to theta. The observations provide direct evidence that theta-related rhythmic hyperpolarization of principal cells is brought by the rhythmically discharging interneurons. Furthermore, the findings in which interneurons were also paced by rhythmic inhibitory postsynaptic potentials during theta suggest that they were periodically hyperpolarized by their GABAergic septal afferents.

• The Korean Journal of Physiology and Pharmacology
• /
• 제7권2호
• /
• pp.59-63
• /
• 2003

The medial vestibular nucleus (MVN) neurons are controlled by excitatory synaptic transmission from the vestibular afferent and commissural projections, and by inhibitory transmission from interneurons. Spontaneous synaptic currents of MVN neurons were studied using whole cell patch clamp recording in slices prepared from 13- to 17-day-old rats. The spontaneous inhibitory postsynaptic currents (sIPSCs) were significantly reduced by the $GABA_A$ antagonist bicuculline ($20{\mu}M$), but were not affected by the glycine antagonist strychnine ($1{\mu}M$). The frequency, amplitude, and decay time constant of sIPSCs were $4.3{\pm}0.9$ Hz, $18.1{\pm}2.0$ pA, and $8.9{\pm}0.4$ ms, respectively. Spontaneous excitatory postsynaptic currents (sEPSCs) were mediated by non-NMDA and NMDA receptors. The specific AMPA receptor antagonist GYKI-52466 ($50{\mu}M$) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. The AMPA mediated sEPSCs were characterized by low frequency ($1.5{\pm}0.4$ Hz), small amplitude ($13.9{\pm}1.9$ pA), and rapid decay kinetics ($2.8{\pm}0.2$ ms). The majority (15/21) displayed linear I-V relationships, suggesting the presence of GluR2-containing AMPA receptors. Only 35% of recorded MVN neurons showed NMDA mediated currents, which were characterized by small amplitude and low frequency. These results suggest that the MVN neurons receive excitatory inputs mediated by AMPA, but not kainate, and NMDA receptors, and inhibitory transmission mediated by $GABA_A$ receptors in neonatal rats.

• The Korean Journal of Physiology and Pharmacology
• /
• 제22권1호
• /
• pp.71-80
• /
• 2018

In patients with epilepsy, depression is a common comorbidity but difficult to be treated because many antidepressants cause pro-convulsive effects. Thus, it is important to identify the risk of seizures associated with antidepressants. To determine whether paroxetine, a very potent selective serotonin reuptake inhibitor (SSRI), interacts with ion channels that modulate neuronal excitability, we examined the effects of paroxetine on Kv3.1 potassium channels, which contribute to high-frequency firing of interneurons, using the whole-cell patch-clamp technique. Kv3.1 channels were cloned from rat neurons and expressed in Chinese hamster ovary cells. Paroxetine reversibly reduced the amplitude of Kv3.1 current, with an $IC_{50}$ value of $9.43{\mu}M$ and a Hill coefficient of 1.43, and also accelerated the decay of Kv3.1 current. The paroxetine-induced inhibition of Kv3.1 channels was voltage-dependent even when the channels were fully open. The binding ($k_{+1}$) and unbinding ($k_{-1}$) rate constants for the paroxetine effect were $4.5{\mu}M^{-1}s^{-1}$ and $35.8s^{-1}$, respectively, yielding a calculated $K_D$ value of $7.9{\mu}M$. The analyses of Kv3.1 tail current indicated that paroxetine did not affect ion selectivity and slowed its deactivation time course, resulting in a tail crossover phenomenon. Paroxetine inhibited Kv3.1 channels in a use-dependent manner. Taken together, these results suggest that paroxetine blocks the open state of Kv3.1 channels. Given the role of Kv3.1 in fast spiking of interneurons, our data imply that the blockade of Kv3.1 by paroxetine might elevate epileptic activity of neural networks by interfering with repetitive firing of inhibitory neurons.

• Journal of Korean Biological Nursing Science
• /
• 제24권2호
• /
• pp.77-85
• /
• 2022

Purpose: Aging process comes with cognitive impairment due to decreased neuronal cell number, activity, and neuronal circuit. Alteration of inhibitory neurons contributes to cognitive impairment in normal aging and is responsible for disrupting the excitation/inhibition balance by reducing the synthesis of gamma-aminobutyric acid (GABA). Morus nigra (Mulberry) is a natural physiologically active substance that has been proven to have anti-oxidant, anti-diabetic, and anti-inflammatory effects through many studies. This study aimed to evaluate the effects of the mulberry extract (ME) on cognitive function through anti-oxidant enzyme and GABAergic neuronal activity in aged rat brain. Methods: Sprague Dawley rats were randomly assigned as the young group (8 weeks, n= 8), aging group (67 weeks, n= 8), and aging+ mulberry extract group (67 weeks, n= 8). The aging+ mulberry extract group was orally administered 500 mg/kg/d mulberry extract for 6 weeks. Results: The aging+ mulberry extract group improved spatial and short-term memory. The antioxidant potential of ME increased the expression of superoxide dismutase-1 (SOD-1) and decreased inducible nitric oxide synthase (iNOS). Also, the aging+ mulberry extract group significantly increased the expression of GABAergic interneuron in hippocampus cornu ammonis1 (CA1) compared to the aging group. Conclusion: The number of GABAergic inhibitory interneurons was deceased and memory functions in the aging process, but those symptoms were improved and restored by mulberry extract administration.

• The Korean Journal of Physiology and Pharmacology
• /
• 제21권5호
• /
• pp.487-493
• /
• 2017

The anterior cingulate cortex (ACC) is known for its role in perception of nociceptive signals and the associated emotional responses. Recent optogenetic studies, involving modulation of neuronal activity in the ACC, show that the ACC can modulate mechanical hyperalgesia. In the present study, we used optogenetic techniques to selectively modulate excitatory pyramidal neurons and inhibitory interneurons in the ACC in a model of chronic inflammatory pain to assess their motivational effect in the conditioned place preference (CPP) test. Selective inhibition of pyramidal neurons induced preference during the CPP test, while activation of parvalbumin (PV)-specific neurons did not. Moreover, chemogenetic inhibition of the excitatory pyramidal neurons alleviated mechanical hyperalgesia, consistent with our previous result. Our results provide evidence for the analgesic effect of inhibition of ACC excitatory pyramidal neurons and a prospective treatment for chronic pain.

• Nuclear Medicine and Molecular Imaging
• /
• 제41권2호
• /
• pp.166-171
• /
• 2007

GABA is primary an inhibitory neurotransmitter that is localized in inhibitory interneurons. GABA is released from presynaptic terminals and functions by binding to GABA receptors. There are two types of GABA receptors, $GABA_{A}-receptor$ that allows chloride to pass through a ligand gated ion channel and $GABA_{B}-receptor$ that uses G-proteins for signaling. The $GABA_{A}$-receptor has a GABA binding site as well as a benzodiazepine binding sites, which modulate $GABA_{A}$-receptor function. Benzodiazepine GABAA receptor imaging can be accomplished by radiolabeling derivates that activates benzodiazepine binding sites. There has been much research on flumazenil (FMZ) labeled with $^{11}C-FMZ$, a benzodiazepine derivate that is a selective, reversible antagonist to GABAA receptors. Recently, $^{18}F-fluoroflumazenil$ (FFMZ) has been developed to overcome $^{11}C's$ short half-life. $^{18}F-FFMZ$ shows high selective affinity and good pharmacodynamics, and is a promising PET agent with better central benzodiazepine receptor imaging capabilities. In an epileptic focus, because the GABA/benzodiazepine receptor amount is decreased, using $^{11}C-FMZ$ PET instead of $^{18}F-FDG$ PET, restrict the foci better and may also help find lesions better than high resolution MR. $GABA_{A}$ receptors are widely distributed in the cerebral cortex, and can be used as an viable neuronal marker. Therefore it can be used as a neuronal cell viability marker in cerebral ischemia. Also, GABA-receptors decrease in areas where neuronal plasticity develops, therefore, $GAB_{A}$ imaging can be used to evaluate plasticity. Besides these usages, GABA receptors are related with psychological diseases, especially depression and schizophrenia as well as cerebral palsy, a motor-related disorder, so further in-depth studies are needed for these areas.

• 생명과학회지
• /
• 제16권5호
• /
• pp.750-758
• /
• 2006

칼슘 결합 단백질 calretinin은 칼슘의 완충작용에 중요한 역할을 한다고 알려져 있다. 최근에 우리는 햄스터 상구의 superficial layer에서 calretinin과 면역반응(immunoreactive)을 일으키는 신경세포의 형태, 분포와 안구적출 후 calretinin 면역반응의 영향에 대해 보고한 바 있다. 본 연구에서는, 상구의 deeper layer에서 면역세포화학 방법을 이용하여 면역표지 된 세포의 분포와 유형 그리고 안구적출 후 변화의 양상을 기술한다. 또한 중추 신경계에서 주요 억제성 신경전달물질인 GABA를 사용하여 calretinin 면역표지 된 세포와 비교하였다. Superficial layer와 비교하여, deeper layer는 calretinin 면역 반응을 일으키는 많은 신경세포들이 분포한다. 이 신경세포들은 두 층을 형성하며, 그 중 첫 번째 층은 intermediate gray layer에서 뚜렷한 층 구조를 나타내었다. 두 번째 층은 deep gray layer에서 발견되었다. 면역표지 된 신경세포는 형태학적으로 매우 다양하며, 수직 방추모양, 성상, 둥근/타원형 그리고 수평 신경세포를 포함한다. Superficial layer와 비교하여, 안구적출은 deeper layer에서 calretinin 면역반응의 분포에 영향이 없는 것으로 보여진다. 두 가지 색을 이용한 면역 형광법은 calretinin 면역반응 신경세포들이 하나도 GABA항체와 함께 표지 되지 않는 것을 보여준다. 본 연구 결과는 햄스터 상구에서 calretinin 함유 신경세포는 특이한 sublaminar 구조를 이루고 있는 것을 보여준다. 본 연구 결과는 또한 햄스터 상구에서 calretinin 면역 반응 신경세포들은 GABAergic interneuron이 하나도 없는 것을 증명한다. 많은 calretinin 면역 반응 세포들은 대부분 뇌의 다른 부분에서는 GABAergic interneuron 인데 비해, 햄스터 상구에서의 본 연구 현상은 예외적이다.

• The Korean Journal of Pain
• /
• 제11권1호
• /
• pp.23-29
• /
• 1998

Background: The present study was conducted to investigate effects of microinjection of bicuculline, GABA-A receptor antagonist, into the brain stem nuclei on the dorsal horn neuron responsiveness in rats with an experimental peripheral neuropathy. Methods: An experimental neuropathy was induced by a unilateral ligation of L5~L6 spinal nerves of rats. After 2~3 weeks after the surgery, single-unit recording was made from wide dynamic range (WDR) neurons in the spinal cord dorsal horn. Results: Responses of WDR neurons to both noxious and innocuous mechanical stimuli applied to the somatic receptive fields were enhanced on the nerve injured side. These enhanced responsiveness of WDR neurons were suppressed by microinjection of bicuculline into periaqueductal gray(PAG) or nucleus reticularis gigantocellularis(Gi). A similar suppression was also observed when morphine was microinjected into PAG or Gi. Suppressive action by Gi-bicuculline was reversed by naloxonazine, ${\mu}$-opioid receptor antagonist, microinjected into PAG whereas PAG-bicuculline induced suppression was not affected by naloxonazine injection into Gi. Gi-bicuculline induced suppression were reversed by a transection of dorsolateral funiculus(DLF) of the spinal cord. Conclusions: The results suggest that endogenous opioids, via acting on GABAergic interneurons in PAG and Gi, may be involved in the control of neuropathic pain by activating the descending inhibitory pathways that project to the spinal dorsal horn through DLF to inhibit the responsiveness of WDR neurons.

• 대한소아치과학회지
• /
• 제27권1호
• /
• pp.7-14
• /
• 2000

가바성 억제 신경세포는 해마의 정상적인 기능을 조절하는데 중요한 역할을 하며 해마 병변을 유발하는 중요한 요소이다. 본 연구는 in vivo 실험법을 사용하여 해마 CA1 영역에서의 전기 생리학적 반응을 측정함으로써 가바성 신경세포의 기능을 분석하고 이를 슬라이스 실험법과 비교하고자 하였다. Fimbria-fonix 전기자극시 전형적인 population spike가 나타났고 $10{\sim}M$ bicuculline 존재하에서는 전기자극에 의해 burst 형태의 population spike가 나타났다. Population spike의 크기는 자극 강도에 비례하였으며 그 숫자도 bicuculline 전극사용시와 같이 동일한 양상을 보였다. CA1 영역의 흥분성 수준을 측정하기 위해 paired-pulse 자극을 하였는데 짧은 자극 간격에서 억제성 반응을 보였고 burst형태의 afterdischarge를 나타내었다. CA1 영역에서 in vivo실험법을 사용한 가바성 신경세포반응의 결과는 추체세포의 흥분성 조절을 효과적으로 분석할 수 있으며 in vitro 실험법에 비해 기능적 평가가 더욱 이상적임을 알 수 있다.