• The Korean Journal of Physiology and Pharmacology
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• 제22권4호
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• pp.419-425
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• 2018

The superficial dorsal horn of the spinal cord plays an important role in pain transmission and opioid activity. Several studies have demonstrated that opioids modulate pain transmission, and the activation of ${\mu}$-opioid receptors (MORs) by opioids contributes to analgesic effects in the spinal cord. However, the effect of the activation of MORs on GABAergic interneurons and the contribution to the analgesic effect are much less clear. In this study, using transgenic mice, which allow the identification of GABAergic interneurons, we investigated how the activation of MORs affects the excitability of GABAergic interneurons and synaptic transmission between primary nociceptive afferent and GABAergic interneurons. We found that a selective ${\mu}$-opioid agonist, [$D-Ala^2$, $NMe-Phe^4$, Gly-ol]-enkephanlin (DAMGO), induced an outward current mediated by $K^+$ channels in GABAergic interneurons. In addition, DAMGO reduced the amplitude of evoked excitatory postsynaptic currents (EPSCs) of GABAergic interneurons which receive monosynaptic inputs from primary nociceptive C fibers. Taken together, we found that DAMGO reduced the excitability of GABAergic interneurons and synaptic transmission between primary nociceptive C fibers and GABAergic interneurons. These results suggest one possibility that suppression of GABAergic interneurons by DMAGO may reduce the inhibition on secondary GABAergic interneurons, which increase the inhibition of the secondary GABAergic interneurons to excitatory neurons in the spinal dorsal horn. In this circumstance, the sum of excitation of the entire spinal network will control the pain transmission.

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

• BMB Reports
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• 제46권2호
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• pp.80-85
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• 2013

We investigated the temporal alterations of adrenocorticotropic hormone (ACTH) immunoreactivity in the hippocampus after seizure onset. Expression of ACTH was observed within inter-neurons in the pre-seizure group of seizure sensitive gerbils, whereas its immunoreactivities were rarely detected in seizure resistant gerbil. Three hr after the seizure, ACTH immunoreac-tivity was significantly increased in interneurons within all hippocampal regions. On the basis of their localization and morphology through immunofluorescence staining, these cells were identified as $GABA_A$ ${\alpha}1$-containing interneurons. At the 12 hr postictal period, ACTH expression in these regions was down-regulated, in a similar manner to the pre-seizure group of gerbils. These findings support the increase in ACTH synthesis that contributes to a reduction of corticotrophin-releasing factor via the negative feedback system which in turn provides an opportunity to enhance the excitability of GABAergic interneurons. Therefore, ACTH may play an important role in the reduction of excitotoxicity in all hippocampal regions.

• 생명과학회지
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• 제16권5호
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• pp.750-758
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• 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.

• International Journal of Oral Biology
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• 제30권2호
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• pp.71-76
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• 2005

The mesencephalic trigeminal nucleus (Mes V) contains cell bodies of primary afferent sensory neurons that relay proprioceptive information from the periodontium and masticatory muscles and function as typical sensory neurons or potentially as integrative interneurons. In the present study, we studied these two potential functions using combined experimental approaches of retrograde labeling and whole cell patch clamp recording. Mes V neurons that presumably originate from periodontal nerve fibers in subsets of Mes V nucleus were identified by retrograde labeling with a fluorescent dye, DiI, which was applied onto inferior alveolar nerve. These cells were elliptical perikarya shaped cells about $40{\mu}m$ in diameter. In these neurons, we measured high voltage-activated calcium channel (HVACC) currents. $GABA_B$ agonist, baclofen, inhibited calcium currents, and the HVACC currents inhibition by baclofen was voltage-dependent, exhibited prepulse facilitation, indicating that it was mediated by $G_i/_G_o$ protein. Taken together, our results demonstrate that Mes V neurons not only have cell bodies originating from periodontium, but also receive synaptic inputs including GABAergic neurons suggesting that Mes V neurons function as both primary sensory neurons and integrative interneurons.

• 대한소아치과학회지
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• 제25권4호
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• pp.671-682
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• 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.

• BMB Reports
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• 제53권4호
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• pp.234-239
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• 2020

Epilepsy is a chronic neurological disease characterized by spontaneous recurrent seizures and caused by various factors and mechanisms. Malfunction of the olfactory bulb is frequently observed in patients with epilepsy. However, the morphological changes in the olfactory bulb during epilepsy-induced neuropathology have not been elucidated. Therefore, in the present study, we investigated the expression of parvalbumin (PV), one of the calcium-binding proteins, and morphological changes in the rat main olfactory bulb (MOB) following pilo-carpine-induced status epilepticus (SE). Pilocarpine-induced SE resulted in neuronal degeneration in the external plexiform layer (EPL) and glomerular layer (GL) of the MOB. PV immunoreactivity was observed in the neuronal somas and processes in the EPL and GL of the control group. However, six hours after pilocarpine administration, PV expression was remarkably decreased in the neuronal processes compared to the somas and the average number of PV-positive interneurons was significantly decreased. Three months after pilocarpine treatment, the number of PV-positive interneurons was also significantly decreased compared to the 6 hour group in both layers. In addition, the number of NeuN-positive neurons was also significantly decreased in the EPL and GL following pilocarpine treatment. In double immunofluorescence staining for PV and MAP2, the immunoreactivity for MAP2 around the PV-positive neurons was significantly decreased three months after pilocarpine treatment. Therefore, the present findings suggest that decreases in PV-positive GABAergic interneurons and dendritic density in the MOB induced impaired calcium buffering and reciprocal synaptic transmission. Thus, these alterations may be considered key factors aggravating olfactory function in patients with epilepsy.

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

• Molecules and Cells
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• 제21권1호
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• pp.34-41
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• 2006

The neuronal localization of alpha-amino-3-hydroxyl-5-methyl-4-isoxazole propionic acid (AMPA) glutamate receptor (GluR) subunits is vital as they play key roles in the regulation of calcium permeability. We have examined the distribution of the calcium permeable AMPA glutamate receptor subunit GluR1 in the mouse visual cortex immunocytochemically. We compared this distribution to that of the calcium-binding proteins calbindin D28K, calretinin, and parvalbumin, and of GABA. The highest density of GluR1-immunoreactive (IR) neurons was found in layers II/III. Enucleation appeared to have no effect on the distribution of GluR1-IR neurons. The labeled neurons varied in morphology; the majority were round or oval and no pyramidal cells were labeled by the antibody. Two-color immunofluorescence revealed that 26.27%, 10.65%, and 40.31% of the GluR1-IR cells also contained, respectively, calbindin D28K, calretinin, and parvalbumin. 20.74% of the GluR1-IR neurons also expressed GABA. These results indicate that many neurons that express calcium-permeable GluR1 also express calcium binding proteins. They also demonstrate that one fifth of the GluR1-IR neurons in the mouse visual cortex are GABAergic interneurons.

• 대한소아치과학회지
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• 제27권1호
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• pp.7-14
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• 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.