An Immunohistochemical Study of ErbB4 Receptor in Alzheimer’s Disease Hippocampus

우란숙,Ji-Hye Lee,Sung-Sam Jung,Yoon-Jung Choy2,Ha-Nul Yu,Kyoung-Min Oh,송대용,Jin Kwon,Tai-Kyoung Baik 대한해부학회 2009 Anatomy & Cell Biology Vol.42 No.4

Neuregulin-1 (NRG1) signaling participates in numerous neurodevelopmental processes. Although ErbB4, a key NRG1 receptor, is expressed in multiple regions in the adult animal brain, little is known about its expression in aged human brain. We show that ErbB4 immunoreactivity was shown regional difference in the hippocampus of age-matched control and that the distribution of these molecules was altered in Alzheimer’s disease (AD) brains. Immunohistochemical characterization of the distribution of ErbB4 receptor in the hippocampus relative to pathology staging were performed in age-matched control (Braak stage Ⅰ/Ⅱ, n=5), early AD (Braak stage Ⅲ/Ⅳ, n=5) and advanced AD(Braak stage Ⅴ/Ⅵ, n=10). The intensity of ErbB4 immunoreactivity was higher in neurons of the CA2 than that in CA1 or CA3 in the age-matched control. Particularly, in the early AD, ErbB4 immunoreactivity was significantly increased in the apoptotic cells of the CA2 field. In the advanced AD, ErbB4 immunostaining was more intense in the apoptotic cell of the CA2 field. In the dentate gyrus (DG), ErbB4-positive granular cell density was gradually increased in proportion to the progression of pathology of AD brains. We have also found that ErbB4 immunostaining was increased in the nucleus, suggesting that the presenilin-dependent cleavage of ErbB4 generates the soluble ErbB4 ICD (intracellular domain) that translocalized to the nucleus. Together, these results provide the immunohistochemical analysis of ErbB4 receptor in the human hippocampus staged by the progression of pathology of AD.

Expression of ErbB4 in the apoptotic neurons of Alzheimer’s disease brain

우란숙,Ji-Hye Lee,Ha-Nul Yu,송대용,백태경 대한해부학회 2011 Anatomy & Cell Biology Vol.43 No.4

Neuregulin-1 (NRG1) signaling participates in the synaptic plasticity, maintenance or regulation of adult brain. Although ErbB4, a key NRG1 receptor, is expressed in multiple regions in the adult animal brain, little is known about its localization in Alzheimer’s disease (AD) brains. We previously reported that ErbB4 immunoreactivity showed regional difference in the hippocampus of age-matched control. In the present paper, immunohistochemical characterization of the distribution of ErbB4 receptor in the hippocampus relative to pathology staging were performed in age-matched control (Braak stage 0, n=6) and AD (Braak stage I/V, n=10). Here, we found that ErbB4 immunoreactivity was significantly increased in apoptotic hippocampal pyramidal neurons in the brains of AD patients, compared to those of age-matched control subjects. In AD brains, ErbB4 immunoreactivity was demonstrated to colocalize with the apoptotic signal Bax in apoptotic hippocampal pyramidal neurons. These results suggest that up-regulation of ErbB4 immunoreactivity in apoptotic neuron may involve in the progression of pathology of AD.

신경계에서의 Neuregulins의 기능과 신호전달 경로

우란숙(Ran-Sook Woo) 대한해부학회 2008 Anatomy & Cell Biology Vol.41 No.2

신경계통에서 중요한 역할을 하고 있는 Neuregulins (NRGs)이라는 단백질에 대한 최근의 연구성과들을 간략하게 고찰하고자 한다. NRGs는 신경세포의 초기운명결정, 분화, 이동, 신경전달물질 수용체들의 발현 및 연접(synapse)의 활성을 조절하고 위성세포(satellite cell), 신경집세포, 희소돌기아교세포(oligodendrocyte)의 생존에 중요한 역할을하는 등 신경계에서 다양한 역할을 수행하고 있다. NRGs과 상호작용하는 ErbB tyrosine kinase수용체는 ErbB2, ErbB3, ErbB4가 있으며, 이종- 또는 동종이합체를 형성하여 세포내 신호전달을 활성화 한다. 최근 NRG1과 그 수용체 중 하나인 ErbB4는 정신분열증의 후보 유전자(candidate gene)중 하나로 알려짐으로써 그 중요성이 더욱 강조되었다. 이 종설에서는 발생과정 및 성체에서의 NRGs의 기능과 신경계질환과의 관련성에 초점을 두어 고찰하기로 한다. The neuregulins (NRGs) are a family of proteins containing an epidermal growth factor (EGF)-like motif that mediates important functions not only in the nervous system but also in the heart, breast and other organ systems. NRG1 was first found to function in the nervous system in the proliferation of Schwann cells, and in the regulation of nicotinic acetylcholine receptor (AChR) transcription at the neuromuscular junction (NMJ). NRGs have multiple biological functions. In the brain, NRG signaling regulates early fate determination, differentiation, migration, synaptic activity of target cell and the expression of other neurotransmitter receptors and survival of satellite cells, Schwann cells and oligodendrocytes. There is also evidence for involvement of NRGs signaling in the pathogenesis of disease, including breast cancer, multiple sclerosis, traumatic brain injury and Hirschsprung’s disease. Especially, both NRG1 and ErbB4 have emerged as susceptibility genes of schizophrenia. In this review, I will summarize the latest findings regarding the spectrum of NRG-ErbB action and signaling pathways in the developing and adult nervous system.

A rare bilateral variation on the dorsum of the hand: extensor digitorum brevis manus and extensor medii proprius

Dong Hyun Lee,Jae Hee Lee,우란숙,Dae Yong Song,Tai Kyung Baik,유홍일 대한해부학회 2019 Anatomy & Cell Biology Vol.52 No.1

A 78-year-old male cadaver showed bilateral anomalous muscles on the dorsum of the hand. An extensor digitorum brevis manus was noted on the dorsum of the right hand. It originated from the distal end of the radius and the radiocarpal joint ligaments and inserted into the metacarpophalangeal joint of the third digit. On the dorsum of the left hand, an extensor digiti medii proprius was identified. It originated from the distal third of the ulna near the extensor indicis proprius and the interosseous membrane and inserted into the metacarpophalangeal joint of the third digit. Awareness of these combined muscular variation would be helpful in understanding the identification of digital extensors and in requiring careful consideration for the reconstruction surgery of the hand.

Amyloid Precursor Protein Binding Protein-1 Is Up-regulated in Brains of Tg2576 Mice

양현정,주유영,홍보현,하성지,김혜선,우란숙,이상형,서유훈 대한약리학회 2010 The Korean Journal of Physiology & Pharmacology Vol.14 No.4

Amyloid precursor protein binding protein-1 (APP-BP1) binds to the carboxyl terminus of amyloid precursor protein and serves as a bipartite activation enzyme for the ubiquitin-like protein, NEDD8. Previously, it has been reported that APP-BP1 rescues the cell cycle S-M checkpoint defect in Ts41 hamster cells, that this rescue is dependent on the interaction of APP-BP1 with hUba3. The exogenous expression of APP-BP1 in neurons has been reported to cause DNA synthesis and apoptosis via a signaling pathway that is dependent on APP-BP1 binding to APP. These results suggest that APP-BP1 overexpression contributes to neurodegeneration. In the present study, we explored whether APP-BP1 expression was altered in the brains of Tg2576 mice, which is an animal model of Alzheimer’s disease. APP-BP1 was found to be up-regulated in the hippocampus and cortex of 12 month-old Tg2576 mice compared to age-matched wild-type mice. In addition, APP-BP1 knockdown by siRNA treatment reduced cullin-1 neddylation in fetal neural stem cells, suggesting that APP-BP1 plays a role in cell cycle progression in the cells. Collectively, these results suggest that increased expression of APP-BP1, which has a role in cell cycle progression in neuronal cells, contributes to the pathogenesis of Alzheimer’s disease.

Neuregulin-1 Protects Neuronal Cells Against Damage due to CoCl2-Induced Hypoxia by Suppressing Hypoxia-Inducible Factor-1α and P53 in SH-SY5Y Cells

유승연,유지영,김한별,백태경,이준호,우란숙 대한배뇨장애요실금학회 2019 International Neurourology Journal Vol.23 No.S1

Hypoxia-mediated neurotoxicity contributes to various neurodegenerative disorders, including Alzheimer disease. Neuregulin-1 (NRG1) plays an important role in the development and plasticity of the brain. The aim of the present study was to investigate the neuroprotective effect and the regulating hypoxic inducible factor of NRG1 in cobalt chloride (CoCl2) induced hypoxia. Methods: Hypoxia was induced in SH-SY5Y cells by CoCl2 treatment. SH-SY5Y cells were pretreated with NRG1 and then treated with CoCl2. Western blotting, immunocytochemistry, and lactate dehydrogenase (LDH) release assays were performed to examine neuroprotective properties of NRG1 in SH-SY5Y cells. Results: Our data showed that CoCl2 induced cytotoxicity and changes of hypoxia-inducible factor-1α (HIF-1α) and p53 expression in SH-SY5Y cells. However, pretreatment with NRG1 inhibited CoCl2-induced accumulation of HIF-1α and p53 stability. In addition, NRG1 significantly attenuated cell death of SH-SY5Y induced by CoCl2. Conclusions: NRG1 can regulate HIF-1α and p53 to protect neurons against hypoxic damage.

국소뇌허혈 후 허혈경계영역에서의 Activating Transcription Factor 3의 발현

송대용(Dae-Yong Song),오경민(Kyoung-Min OH),이지혜(Ji-Hye Lee),우란숙(Ran-Sook Woo),이윤정(Yun-Jeong Lee),한정태(Jung-Tae Han),백태경(Tai-Kyoung Baik) 대한해부학회 2008 Anatomy & Cell Biology Vol.41 No.3

c-Jun이나 fos와 같은 immediate early gene (IEGs)은 여러종류의 세포손상에 대해 즉각적으로 발현하여 손상 받은 신경세포의 운명을 결정함에 중요한 역할을 담당하는 것으로 알려져 있다. IEGs 중 activating transcription factor 3 (ATF3)는 다양한 신경손상에 반응하여 발현되며, 손상된 신경세포의 내∙외적 환경에 따라 신경세포의 생존 혹은 신경세포의 사멸에도 관여할 수 있기 때문에 매우 흥미로운 단백질이다. 그러나 아직까지 뇌허혈손상에서 신경세포내 ATF3의 발현 및 역할에 대한 연구는 매우 드물다. 이에 이 연구는 중간대뇌동맥 폐색-재관류로 야기된 국소적 뇌허혈손상에서 초래되는 신경조직의 형태적 변화와 신경세포에서 일어나는 ATF3 발현의 변화를 조사하기 위하여 시도되었다. 허혈-재관류손상이 야기된 흰쥐의 뇌를 절취한 후 2mm 간격으로 연속 관상절편을 제작하고 triphenyltetrazolium chloride (TTC) 염색을 시행하여 중간대뇌동맥 폐색-재관류에 따른 뇌손상의 범위를 확인하였으며, 허혈중심영역 (ischemic core region) 및 허혈경계영역 (ischemic penumbra region)으로 구분하여 관찰하였다. Haematoxylin 및 eosin 염색결과 양 영역 모두에서 핵농축과 호염기성 신경세포체 변성과 같은 세포사멸을 암시하는 소견을 나타내는 신경세포를 다수 확인할 수 있었으며, 또한 많은 수의 아교세포가 동원된 소견을 제시할 수 있었다. 동원된 아교세포의 종류 를 동정하기 위해 GFAP 및 OX42에 대한 항체를 이용한 면역조직화학염색을 실시한 결과, 활성 별아교세포 및 미세아교세포가 뇌손상부위에 운집되어 있었다. 그리고 ATF3 면역조직화학염색을 실시한 결과, ATF3에 면역양성반응을 보이는 신경세포들은 허혈-재관류에 의한 손상이 야기된 대뇌겉질에서만 관찰되었으며, 대조군으로 사용한 반대측 대뇌겉질에서는 관찰되지 않았다. 특히 ATF3 면역양성세포는 허혈중심영역보다 허혈경계영역에서 더 빈번히 관찰되었다. 허혈중심영역에서의 신경세포사멸은 주로 세포괴사(necrosis)에 의해, 허혈경계영역에서의 세포사멸은 주로 세포자멸사(apoptosis)에 의해 유도된다는 여러 학자들의 보고를 참고하면 이번 연구결과는 ATF3가 허혈에 의해 야기되는 세포자멸사 혹은 세포생존 신호전달과정에 관여하여 세포의 운명을 결정하는 매우 중요한 IEGs 중 하나일 것임을 강력히 시사한다. It has been demonstrated that some of immediate early genes (IEGs) such as c-Jun or fos are induced immediately following neuronal injury and they play an important role in determining the fate of the injured neurons. Of IEGs, the activating transcription factor 3 (ATF3) is focused by many investigators, because they are expressed in various types of neural insults and have been known to serve a diverse function in both neuronal survival and death. However, little is known about the functional role of ATF3 in ischemic brain injury. So in this study, the authors examined the expression pattern of the activating transcription factor 3 (ATF3) following middle cerebral artery (MCA) occlusion-reperfusion injury. According to the findings obtained by triphenyltetrazolium chloride (TTC) stains, the authors have classified the infarcted area into two regions, the ischemic core region and the ischemic penumbra region. In both regions, many neurons underwent neuronal degeneration, characterized by the shrunken nuclei with eosinophilic perikaryon. The H & E stain also demonstrated the increased number of probable activated astrocytes and microglia in the ischemic brain regions and this was confirmed by GFAP- and OX42-immunohistochemistry. Immunohistochemical study for ATF3 also demonstrated the specific upregulation of ATF3 in the nuclei of neurons under ischemic injury, but not in those of the contralateral regions. Interestingly, the number of the ATF3 positive neurons in the ischemic penumbra regions outnumbered that of the ischemic core regions. Based on many reports that the neuronal death in ischemic penumbra region is caused by programed cell death rather than by necrosis which is main cause of neuronal death in ischemic core region, our results could suggest that the ATF3 is an important IEGs which determine the fate of the ischemic neurons.

Case Report of the Bilateral Absence of the Musculocutaneous Nerve Combined with the Unilateral Brachioradial Artery

Dae-Yong Song(송대용),Kyoung-Min Oh(오경민),Ji-Hye Lee(이지혜),Ran-Sook Woo(우란숙),Ha-Nul Yu(유하늘),Tai-Kyoung Baik(백태경) 대한체질인류학회 2009 대한체질인류학회지 Vol.22 No.4

해부학실습 과정 중, 76세 한국인 남성 시신에서 양쪽 팔 모두에서 근육피부신경이 없고, 한쪽 팔에서 위팔노동맥이 형성된 사실을 발견하였다. 겨드랑꼭대기에서 팔신경얼기의 가쪽신경다발이 근육피부신경을 내지 않고 모두 정중신경으로 합쳐졌다. 정상적인 경우 근육피부신경에 의해 지배받는 위팔의 굽힘근들이 정중신경에서 기원한 두 가닥의 신경가지에 의해 지배받았다. 이 중 먼쪽 신경가지는 계속되어 가쪽아래팔피부신경이 되었다. 또한 왼쪽 팔의 노동맥이 위팔동맥의 중간 상분의 일 지점에서 기원하였다. 위팔동맥으로부터 분지되는 지점에서 노동맥은 정중신경의 깊은 곳을 안쪽으로 가로질렀다. 그러나, 팔꿈치 부위에서 노동맥은 다시 정중신경을 앞가쪽으로 가로질러 주행하였다. 팔오금 바로 위에서 노동맥은 위팔동맥과 연결되는 작은 문합가지롤 내었다. 오른팔의 동맥분포는 정상이었다. 근육피부신경의 부재와 위팔노동맥의 변이는 그동안 독립적으로 보고된 바 있다. 그러나 이번 연구에서와 같이 두 변이가 한 시신에서 동시에 발견된 보고는 일찍이 없었다. During the routine gross anatomical dissection, bilateral absence of the musculocutaneous nerve and unilateral brachioradial artery were found in a 76-year-old Korean male cadaver. At the apex of the axilla, the lateral cord of the brachial plexus united into the median nerve without branching off the musculocutaneous nerve. The flexor arm musculatures, normally innervated by the musculocutaneous nerve, were innervated by two separate branches from the median nerve. The distal one continued as the lateral antebrachial cutaneous nerve. In addition, the radial artery of the left arm was originated from the middle one-third of the brachial artery. At bifurcation, it lay deep to the median nerve and crossed it medially. However, at the elbow, it crossed again the median nerve anterolaterally. Just above the cubital fossa, it anastomosed with the brachial artery. The arterial distribution of the right arm was normal. The separate reports which described the absence of the musculocutaneous nerve or brachioradial artery have been reported. However, this combined variation has not been documented until now.

국소적 대뇌허혈 동물모델에서 Diazoxided의 신경보호효과

전영희(Young-Hee Cheon),서병현(Byeong-Hyun Suh),윤아람(A-Ram Yoon),이지혜(Ji-Hye Lee),우란숙(Ran-Sook Woo),송대용(Dae-Yong Song),백태경(Tai-Kyoung Baik) 대한해부학회 2009 Anatomy & Cell Biology Vol.42 No.4

허혈전조건화는 장시간의 허혈 발생 전에 일시적이고 반복적인 허혈을 유도하여 대뇌 손상을 감소시키는 것으로, 사립체의 K?ATP channel opener가 허혈전조건화를 유도하여 허혈세포에서 보호효과를 나타내는 것으로 보고되고 있으나 아직 자세한 기전은 알려져 있지 않다. 이 연구에서는 국소적 대뇌허혈 동물모델에서 허혈 손상시 K?ATP channel opener인 diazoxide 전처치에 의한 신경세포 보호효과의 기전을 밝히고자 하였다. 실험동물로는 300~350g 내외의 Sprague-Dawley계 흰쥐(n=34)를 사용하였으며, 정상대조군과 2시간 허혈군, 24시간 허혈군, diazoxide 전처치후 2시간 허혈군과 diazoxide 전처후 24시간 허혈군으로 세분하였다. 변형된 Longa법을 이용하여 국소적 뇌허혈술을 실시하였으며, diazoxide는 뇌허혈술 15분전에 3mg/kg을 넙다리동맥으로 투여하였다. 중간대뇌동맥 폐쇄에 의해 동측 대뇌겉질 대부분과 줄무늬체에서 뇌경색이 초래되었으며, diazoxide 전처치군에서는 허혈군에 비하여 경색부피가 감소되었다. 동시에 diazoxide 전처치군에서는 경색주변조직에서의 해면체성변형 및 신경세포의 퇴행성변화가 감소하는 소견을 보였다. 한편 2시간 허혈군에서는 정상대조군과 동일하게 TUNEL 염색에 양성반응을 보이는 세포를 관찰할 수 없었으나, 24시간 경과군에서는 다수의 신경세포가 양성반응을 보였다. 허혈군 및 diazoxide 전처치군 모두에서 허혈 2시간째 c-Fos에 면역양성반응을 보이는 신경세포의 수가 크게 증가하였으나, 24시간 경과군에서는 정상대조군 수준으로 다시 감소하였다. 한편 Bcl-2 혹은 pAkt에 면역양성반응으로 보이는 신경세포의 수는 허혈 2시간째부터 허혈대조군에 비해 통계적으로 유의하게 높게 나타났으며, 이러한 현상은 허혈 24시간째까지 지속되었다. 이상의 결과를 토대로, K?ATP channel opener인 diazoxide의 전처치는 허혈 초기 단계부터 세포자멸사 억제단백인 Bcl-2나 pAkt의 활성을 증가시키므로써 신경세포를 보호하고 세포 손상을 지연시킬 수 있을 것으로 여겨진다. Ischemic preconditioning is the earlier stress adaptive response that occurs during repeated episodes of the brief ischemia and reperfusion. It is now well known that this adaptive response can render the neuron more tolerant to the subsequent potential lethal ischemic injury. Although the selective mitochondrial K?ATP channel opener induces protective effects similar to that of ischemic preconditioning, the underlying mechanism is not konown yet. The purpose of this study was to investigate the mechanism of neuroprotective effect of diazoxide, a mitochondrial K?ATP channel opener, pretreatment on a focal cerebral ischemic injury of rat brain. Thirthy-four Sprague-Dawley rats were used. Animals were randomly divided into normal control group, middle cerebral artery (MCA) permanent occulusion group(experimental control group), and diazoxide pretreated group. Animals were sacrified at 2 hours or 24 hours after MCA occulusion injury. For inducing the focal cerebral ischemic injury, the left MCA was occuluded by modified Longa's method. Diazoxide (3mg/kg) was administrated though the femoral artery at 15 minutes earlier to surgical procedures. TTC-stained brain sections of experimental group showed a remarkable infarct injury in the ipsilateral cerebral cortex and striatum. However, the infarction volume of the diazoxide pretreated group was significantly reduced. Accordingly, the number of neurons undergoing eosinophilic degeneration and unclear chromatin condensation was reduced by diazoxide pretreatment. TUNEL-positive neurons were not detected at 2 hours after MCA permanent occlusion but lots of them were observed at 24 hours. The number of c-fos immunoreactive neurons was remarkably increased at 2 hours following MCA permanent occulusion and reduced to the basal level at 24 hours in both experimental control and diazoxide pretreated group. However, the number of Bcl-2 or pAkt immunoreactivitive neurons of the diazoxide pretreated group outnumbered those of the experimental control group at all timepoints in our experiment. In conclusion, the pretreatment of diazoxide, K? channel opener, could have neuroprtective effects on ischemic neurons by upregulating the expression of anti-apoptotic proteins, like Bcl-2 or pAkt.

쥐의 말초신경손상모델로서의 궁둥신경절단모델과 L5 척수신경절단모델의 비교연구

송대용(Dae- Yong Song),이지혜(Ji-Hye Lee),유하늘(Ha-Nul Yu),박채리(Chae-Ri Park),우란숙(Ran-Soak Woo),홍성엽(Sung- Yaup Hong),전영희(Young-Hee Cheon),구형남(Hyung-Nam Goo),백태경(Tai-Kyoung Baik) 대한체질인류학회 2012 해부·생물인류학 (Anat Biol Anthropol) Vol.25 No.1

연구자들은 L5 척수신경만을 선택적으로 절단하고 L5 척수분절을 다른 척수 부위와 구별하여 연구함으로써 기존의 궁둥신경절단 모델의 단점을 보완할 수 있는 새로운 말초신경절단 모델을 제안하고자 이 연구를 수행하였다. 300?350g Sprague Dawley계 흰쥐를 이용하여 4개의 실험군으로 나누어 연구하였다. 1. 궁둥신경 절단군: 궁둥신경이 온종아리신경과 정강신경으로 나눠지는 오금부위에서 궁둥신경을 절단한 군. 2. L5 절단군: L5 척수신경이 L5 척수사이구멍을 통과하여 출현하는 부위에서 L5 척수신경만을 선택적으로 절단한 군. 3. 접합군: L5 척수신경 절단 후 바로 봉합한 군. 4. 대조군: 시술 과정은 동일하게 수행하였으나 신경에 손상을 가하지 않은 군. 그리고 일부 실험동물의 경우에는 L5 척수분절을 확인하기 위하여 L5 척수신경을 절단한 후 FluoroGold를 주입하였다. L4와 L6의 척수신경뿌리를 기준으로 L4~L6 척수분절을 절단하고,40 ㎛의 두께로 관상절편을 제작한 결과 평균 180개 정도의 조직절편을 얻을 수 있었다. 이 중, 약 50개의 절편에서 FluoroGold에 양성반응을 보이는 척 수운동신경세포가 관찰되어 L5 척수분절범위는 50개의 절편, 즉 2mm로 하였다. L5 척수분절은 Cresyl violet 염색에서도 형태적으로 L4 및 L6 척수분절과 구별할 수 있었다. 시술 2주 및 4주 후에 동물을 희생하여 L5 척수 운동경세포의 수를 계수한 결과, 대조군과 비교하여 L5 절단군에서 약 8%의 신경세포 수 감소가 확인되었다. 접합군과 궁둥신경 절단군은 대조군과 비교하여 유의할 만한 변화를 보이지 않았다. 본 연구를 통해 제시한 L5 척수신경절단 모델은 L5 척수운동신경세포에서 기원하는 거의 대부분의 축삭을 절단하고, L5 척수분절에만 국한하여 연구를 수행한다는 점에서 기존의 궁둥신경절단 모델을 기반으로 한 연구 방법에 비해 매우 신뢰도가 높은 연구방법이라 제안하는 바이다. The aim of this study was to propose new more reliable peripheral nerve transection model to overcome the defect of the traditional sciatic axotomy model by specifically transecting L5 spinal nerve just after emerging from the intervertebral foramen and confining analysis area to the L5 spinal segment. The adult male Sprague-Dawley rats, weighing 300?350 g at the time of surgery, were used for the experiments. Four different experimental groups were used. 1. Sciatic nerve transection (Sc-Tx) group: transect the sciatic nerve in the popliteal fossa where it divided into the common peroneal nerve and tibial nerve. 2. L5 spinal nerve transection (L5-Tx) group: L5 spinal nerve was specifically transected. 3. Suture (Su) group: L5 spinal nerve was transected and immediately sutured. 4. Control group: the same surgical procedure with L5 spinal nerve transection group was performed except for the excision of L5 spinal nerve. To distinguish L5 motoneurons from the other level ones, the animals were received the retrograde tracer, FluoroGold into the axotomized proximal nerve stump. Serial coronal frozen sections at 40 ㎛ thick through the L4 to L6 spinal segment was performed and the resultant total number of sections was about 180. Approximate serial 50 sections (approximately 2 mm) could be considered as the L5 segment based on the number of the fluorescent signals (above 20). L5 spinal segment could be differentiated from L4 and L6 segment based on their morphological characteristics under Cresyl violet stain. In L5-Tx group, at 2 and 4 weeks post-transection, the number of L5 spinal motoneurons was reduced by 8%. Meanwhile, Sc-Tx and Su groups showed no statistically notable changes. In this study, the authors could propose more reliable peripheral nerve axotomy model than the conventional sciatic nerve axotomy model by specifically transecting L5 spinal nerve and confining the investigating area within the L5 spinal segment.