癫痫相关局灶性皮质发育不良的临床病理学研究

目的研究癫痫相关局灶性皮质发育不良（FCD）的临床病理学特征。方法对38例2005年在北京宣武医院接受致痫灶外科手术切除治疗并临床病理诊断为FCD患者的临床资料、神经影像学以及病理学资料进行回顾性分析。结果38例患者的平均发病年龄为9．2岁,平均病程为11．9年,发作形式以复杂部分性发作为主。神经影像学检查有21例可见海马硬化、灰质异常信号等改变。组织学具体分型为：FCDⅠA型3例,FCDⅠB型20例,FCDⅡA型5例以及FCDⅡB型5例,另有5例被诊断为轻微皮质发育不良（mild MCD）。从部位来看,FCDⅡ型病变多见于颞叶以外的脑叶（8／10）,尤以额叶多见（5／8）。具有双重病理改变的5例均为FCDⅠB型。在免疫组织化学染色,巨大神经元、未成熟神经元、形态异常神经元及白质内异位神经元均可由NeuN清晰的标记出来。少数气球细胞呈nestin阳性表达。结论FCD是难治性癫痫的常见病理组织学所见,其中又以FCDIB型最为多见,并且可伴有海马硬化。FCDⅠ型和Ⅱ型有着不同的临床病理学以及细胞病理学形特征。     

难治性癫痫患者脑组织中相关耐药蛋白表达情况的比较研究

目的探讨P-糖蛋白、多药耐药相关蛋白和穹隆主蛋白3种蛋白在难治性癫痫相关病变脑组织中的分布、表达部位及其在难治性癫痫发生过程中所发挥的作用。方法取18例难治性癫痫患者（包括局灶性皮质发育不良5例、结节性硬化3例、神经节细胞胶质瘤5例、胚胎发育不良性神经上皮瘤5例）致痫灶手术切除脑组织标本,利用针对上述3种蛋白的抗体进行免疫组织化学EnVision法染色。结果P-糖蛋白主要表达于病灶区域的毛细血管内皮细胞内,多药耐药相关蛋白的表达部位则主要为病灶区域内的神经元成分,而穹隆主蛋白在病变脑组织中的高度表达主要集中于毛细血管内皮细胞和气球细胞,另有部分神经元成分呈弱阳性表达。此外,P-糖蛋白和穹隆主蛋白在肿瘤性病变病灶区域毛细血管内皮细胞中的表达强于非肿瘤性病变,而在神经节细胞胶质瘤和胚胎发育不良性神经上皮瘤的肿瘤性胶质细胞中,多药耐药相关蛋白和穹隆主蛋白的表达情况也不尽相同。结论P-糖蛋白、多药耐药相关蛋白和穹隆主蛋白均参与了难治性癫痫的发生过程,其表达部位不同,作用机制各异。     

胚胎发育不良性神经上皮瘤与皮质发育不良

目的观察胚胎发育不良性神经上皮瘤（DNT）的病理形态学及免疫组织化学特点,探讨其与皮质发育不良之间的关系以及组织来源。方法应用光镜和免疫组织化学EnVision法对14例DNT进行观察分析,并对患者进行长期随访。结果肿瘤位于颞叶的有11例,镜下由神经元和神经胶质成分混合构成,9例可见“特异的胶质神经元结构”。1例为简单型,8例为复杂型,5例为非特异型。11例标本充足的病例10例伴有皮质发育不良改变,表现为分子层和（或）白质内异位神经元数量增多（7例）,分子层内可见成行的外颗粒细胞层残留（4例）,脑皮质的结构异常（10例）,以及出现异常形态的神经细胞。免疫组织化学染色少突胶质样细胞（OLC）均呈现Olig2的免疫反应性,部分OLC表达nestin、微管相关蛋白2、神经丝蛋白、胶质纤维酸性蛋白,但神经元核抗原呈阴性。癫痫控制结果Ⅰ级12例,Ⅱ级2例,无肿瘤复发。结论DNT与皮质发育不良关系密切,应用免疫组织化学染色有助于DNT和皮质发育不良的诊断。     

NMDA受体与癫痫及学习、记忆的关系

谷氨酸为中枢神经系统中兴奋性氨基酸,其离子型受体NMDA受体与癫痫的发生、发展密切相关,并且参与长时程增强(LTP)的产生.本文重点介绍近年对NMDA受体与癫痫关系的研究进展,及与学习、记忆的关系.     

雌激素β受体免疫阳性神经元在成年雌性大鼠脑内的分布

目的　探讨雌激素对神经系统的作用 ,研究雌激素 β受体 (ER β)免疫阳性细胞在雌性大鼠脑内的分布。　方法　应用硫酸镍铵增强显色的免疫组织化学技术。　结果　ER β免疫阳性物质主要位于神经元的细胞核内。最强的免疫阳性信号见于前嗅核、大脑皮质、小脑浦肯野细胞、斜角带垂直部、前庭上核、梨状内核、杏仁外侧核、红核和蓝斑 ;中等强度的染色见于隔内侧核、杏仁皮质后核、海马CA3、CA4区、齿状回、终纹床核、视上核等部位 ;较弱的阳性细胞见于下丘脑核团、屏状核、动眼神经核以及杏仁复合体的部分核团。　结论　雌激素 β受体免疫阳性神经元在成年雌性大鼠脑组织内有较广泛的分布 ,可能参与了雌激素对多种脑功能如学习记忆等的调控     

β淀粉样前体蛋白在难治性癫痫患者脑组织中的表达及其临床意义

目的研究β淀粉样前体蛋白(βAPP)在难治性癫痫(RE)患者脑组织中的表达及其临床意义。方法免疫组织化学染色法检测43例RE患者与5例非癫痫患者脑组织中βAPP的表达水平及其与临床特征的关系。结果βAPP在RE患者脑组织中的表达明显高于非癫痫患者(P0.05),表达水平与病理类型、手术预后有关(P0.05),βAPP水平高者术后再发作的可能性更高,而与性别、年龄、病程、发作频率和类型、病变部位无关(P0.05)。结论βAPP参与难治性癫痫的发生发展,可作为手术预后的判断指标。     

大鼠听皮质NMDA受体亚单位NR2B蛋白质的年龄-依赖性表达

目的：研究sD大鼠生后发育过程中,听皮质神经元NMDA受体亚单位NR2B蛋白质的表达规律。方法：采用免疫组织化学反应和蛋白质印迹技术,分别检测生后1、2、3周和成年动物听皮质神经元NMDA受体亚单位NR2B蛋白质的表达。结果：NR2B阳性神经元在生后第1周密度最高,随着生后周龄增长,NR2B阳性神经元密度递减．3周龄后降至成年动物的低表达水平。结论：大鼠生后发育过程巾．听皮质NR2B亚单位蛋白质呈现年龄-依赖性表达,此结果与mRNA水平上的表达趋势一致。     

前脑缺血再灌流后大鼠海马 NMDA受体亚单位NR1蛋白的表达变化

目的　观察大鼠前脑缺血再灌流后海马各区域NMDA受体亚单位NR1表达的变化和差异 ,探讨NR1在缺血性脑损伤中的作用。　方法　免疫组织化学和图像处理技术。　结果　 1 在前脑缺血再灌流后早期 ,海马各区域NR1的表达水平显著下降 (P <0 0 5 )。CA1区 ,下降趋势持续存在且不可逆 ,直至再灌流后第 7d ,NR1在该区域的染色强度降至对照组的 17% (P <0 0 5 )。CA3区及齿状回 ,NR1的表达下降是可逆的 ,再灌流后 72h ,齿状回的表达恢复正常 ,再灌后第 7d ,CA3区的表达也恢复到对照组的 96 % ,两组间染色强度无显著差异。 2 在迟发性神经元坏死出现前的缺血再灌流的早期 ,NR1在CA1区、CA3区及齿状回表达下降的幅度不一致 ,再灌后 6h以前 ,CA1区的下降幅度明显小于CA3区及齿状回 (P <0 0 5 ) ,再灌后 12h ,CA1区的下降幅度仍低于CA3区 (P <0 0 5 )。结论　短暂性前脑缺血后 ,NR1在海马CA1区、CA3区及齿状回表达下降的幅度和可逆性存在显著差异 ,这种差异可能是造成CA1区缺血敏感性的重要原因。     

乳腺癌中雄激素受体的表达及与雌激素、孕激素受体表达的关系

目的 研究乳腺癌组织中雄激素受体(AR)表达的意义及其与雌激素受体(ER)、孕激素受体(PR)表达的关系.方法 应用免疫组化染色检测200例乳腺癌中AR及ER、PR的表达,并结合相关临床病理指标进行比较分析.结果 乳腺癌组织中有113例表达AR,121例表达ER,109例表达PR.在肿瘤＜2cm者中AR阳性率为66.67％(42/63),肿瘤2～5cm者中AR表达率为55.17％ (64/116),肿瘤＞5cm者AR表达率为33.33％(7/21).组织学分级Ⅰ级者肿瘤AR阳性表达率为67.8％(36/53),组织学分级Ⅱ级及Ⅲ级者肿瘤AR的阳性表达率分别为56.5％(61/108)及36.11％(13/36),Ⅰ级及Ⅲ级间比较差异有统计学意义(P =0.0031);AR表达差异与淋巴转移无相关性.AR在乳腺癌中的表达与ER的表达相关(P＜0.001),而与PR的表达无关(P=0.3280).结论 AR高表达的乳腺癌可能具有较好的预后.     

雌二醇经雌激素受体调控分拣蛋白相关受体A对小鼠海马神经元树突棘密度和突触蛋白表达的影响

目的 探讨雌二醇(E₂)调控分拣蛋白相关受体A(SorLA)表达对小鼠海马神经元树突棘密度和突触蛋白表达的影响及机制。方法 32只C57BL/6雌性小鼠随机分为假手术(sham)组、卵巢切除(OVX)组、卵巢切除+E₂组(OVX+E₂)组、卵巢切除+氟维司琼(Fu)+E₂组(OVX+Fu+E₂)组,通过Western blotting和免疫组织化学染色检测小鼠海马CA1区SorLA表达;40只C57BL/6雌性小鼠随机分为假手术+空白病毒(sham+NC-sgRNA)组、卵巢切除+空白病毒(OVX+NC-sgRNA)组、卵巢切除+空白病毒+E₂(OVX+NC-sgRNA+E₂)组、卵巢切除+SorLA敲降病毒+E₂组(OVX+Sorl1-sgRNA+E₂)组,通过高尔基染色检测小鼠海马CA1区神经元树突棘密度;通过Western blotting和免疫组织化学染色检测小鼠海马CA1区突触后致...     

NMDA and non-NMDA receptors mediate taste afferent inputs to cortical taste neurons in rats

Two main subclasses of ionotropic receptors for excitatory amino acids (EAAs), N-methyl-d-aspartate (NMDA) receptors and non-NMDA receptors, are involved in neurotransmission in the cortex of mammals. To examine whether EAAs are transmitters at the cortical taste area (CTA) in rats and to elucidate which types of the two ionotropic receptors operate at these synapses, we studied the effects of microiontophoretic administration of EAA antagonists on the responses of 64 taste cortical neurons to four basic taste stimuli in urethane-anesthetized rats. Both d-2-amino-5-phosphonovalerate (APV), a selective antagonist for NMDA receptors, and 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), a selective antagonist for non-NMDA receptors, suppressed most of the taste responses. The percentage of neurons suppressed by APV (70.3%) was almost the same as that suppressed by CNQX (64.1%). These suppressive effects were independent of the effects of background discharges during the prestimulus, water-rinsing period. The percentage of neurons suppressed by the antagonists did not differ between any pairs of taste stimuli. The number of neurons possessing both receptors was larger in the granular insular area (area GI), one of the two CTAs, than in the dysgranular insular area (area DI). In addition, taste responses were suppressed by CNQX or by both APV and CNQX in area GI in a significantly larger number of layer V neurons than in area DI. The present results indicate that normal excitatory transmission of taste afferents in the CTA in rats was mediated by both NMDA and non-NMDA receptors. The finding that a large fraction of neurons in the CTA in rats mediated taste information through NMDA receptors in normal transmission might be related to the higher potency of the plasticity observed in the CTA.     

Alterations in NMDA receptors in a rat model of cortical dysplasia

Recent studies have demonstrated an important role for the N-methyl-D-aspartate receptor (NMDAR) in epilepsy. NMDARs have also been shown to play a critical role in hyperexcitability associated with several animal models of human epilepsy. Using whole-cell voltage clamp recordings in brain slices, we studied evoked paroxysmal discharges in the freeze-lesion model of neocortical microgyria. The voltage dependence of epileptiform discharges indicated that these paroxysmal events were produced by a complex pattern of excitatory and inhibitory inputs. We examined the effect of the NMDAR antagonist D-2-amino-5-phosphopentanoic acid (APV) and the NMDA receptor subunit type 2B (NR2B)-selective antagonist ifenprodil on the threshold, peak amplitude, and area of evoked epileptiform discharges in brain slices from lesioned animals. Both compounds consistently raised the threshold for evoking the discharge but had modest effects on the discharge peak and amplitude. For comparison with nonlesioned cortex, we examined the effects of ifenprodil on the epileptiform discharge evoked in the presence of 2 microM bicuculline (partial disinhibition). In slices from nonlesioned cortex, 10 microM ifenprodil had little effect on the threshold whereas 71% of the recordings in bicuculline-treated lesioned cortex showed a >25% increase in threshold. These results suggest that NR2B-containing receptors are functionally enhanced in freeze-lesioned cortex and may contribute to the abnormal hyperexcitability observed in this model of neocortical microgyria.     

Vascular endothelial growth factor‐C modulates cortical NMDA receptor activity in cortical lesions of young patients and rat model with focal cortical dysplasia

Emergence of dysmorphic neurons is the primary pathology in focal cortical dysplasia (FCD) associated pediatric intractable epilepsy; however, the etiologies related to the development and function of dysmorphic neurons are not fully understood. Our previous studies revealed that the expression of vascular endothelial growth factor‐C (VEGF‐C) and corresponding receptors VEGFR‐2, VEGFR‐3 was increased in the epileptic lesions of patients with tuberous sclerosis complex or mesial temporal lobe epilepsy. Here, we showed that the expression of VEGF‐C, VEGFR‐2, and VEGFR‐3 was increased at both mRNA and protein levels in patients with cortical lesions of type I, IIa, and IIb FCD. The immunoreactivity of VEGF‐C, VEGFR‐2 and VEGFR‐3 was located in the micro‐columnar neurons in FCD type I lesions, dysplastic neurons (DNs) in FCD type IIa lesions, balloon cells (BCs) and astrocytes in FCD type IIb lesions. Additionally, the amplitude of evoked‐EPSCs (eEPSC) mediated by NMDA receptor, the ratio of NMDA receptor‐ and AMPA receptor‐mediated eEPSC were increased in the dysmorphic neurons of FCD rats established by prenatal X‐ray radiation. Furthermore, NMDA receptor mediated current in dysmorphic neurons was further potentiated by exogenous administration of VEGF‐C, however, could be antagonized by ki8751, the blocker of VEGFR‐2. These results suggest that VEGF‐C system participate in the pathogenesis of cortical lesions in patients with FCD in association with modulating NMDA receptor–mediated currents.     

PDGF and its receptors following facial nerve axotomy in rats: expression in neurons and surrounding glia

We investigated the expression of platelet-derived growth factor (PDGF) and its receptors in rat facial nuclei following axotomy by in situ hybridization and immunohistochemistry. Facial nuclei were examined on days 3, 6, 12, 19 and 26 postoperatively (p.o.). Strong immunoreactivity for PDGF was found in facial neurons and surrounding astrocytes on the ipsilateral side of the brainstem already after 3 days p.o. and persisted at a high level until day 26 p.o. in rats with a facial nerve cut injury. After crushing of the facial nerve, a similar increase was seen in PDGF immunoreactivity which, however, decreased after day 19 p.o., when reinnervation had occurred. Reactive gliosis appeared on the operated side and was confirmed by an increase in intensity of GFAP staining. The kinetics of PDGF A-chain mRNA expression corresponded to the PDGF immunoreactivity, whereas the B-chain mRNA was present only in the neurons. The PDGF -receptor immunoreactivity as well as the mRNA were detected in scattered glial cells. The density of the PDGF -receptor mRNA expressing glial cells was higher on the injured side, but the intensity of the expression per cell did not change after axotomy. An increase in PDGF -receptor immunoreactivity was seen in the ipsilateral facial nuclei after 3–6 days p.o., however, the increase in the mRNA could not be detected. The staining persisted until day 26 p.o., when transected facial neurons showed heavier staining than those that had been crushed. Furthermore, both mRNA and protein of the -receptor were expressed in the blood vessels after 3–6 days p.o., increasing with time. These results imply a role for PDGF in the regeneration process following nerve injury.     

NMDA受体在癫痫发病机制中的作用

癫痫是慢性反复发作短暂脑功能失调综合征,是神经科常见疾病之一。目前有关癫痫的发病机制尚未阐明。研究表明,癫痫的发生与兴奋性神经递质和抑制性神经递质的失衡有关。谷氨酸作为一种主要的兴奋性神经递质,通过受体介导的兴奋性机制在癫痫的发生过程中具有重要作用。谷氨酸受体可以分为促离子型和促代谢型2类。     

Effects of gamma knife irradiation on the expression of NMDA receptor subunits in rat forebrain

OBJECTIVE: To examine the effects of gamma knife surgery (GKS) on the expression of N-methel-D-asparate receptor (NMDAR) subunits in rat forebrain. MATERIALS AND METHODS: Using stereotactic technique, we performed gamma knife irradiation on the left forebrain of 13 male Wistar rats with a maximum dose of 60 Gy. These animals were raised for 24h, 30 and 60 days before they were killed. Then immunohistochemistry was applied to detect the relative levels of NMDAR subunits (NR1, NR2A, and NR2B) in the target region. RESULTS: The expression of NR1 and NR2A but not NR2B increased significantly in the cortex 30 and 60 days after irradiation. However, no significant differences in the expression of these three subunits were detected in the caudate putamen at all time points. CONCLUSION: gamma knife irradiation induced the upregulation of NMDAR subunits, NR1, and NR2A, which might represent a possible mechanism underlying the therapeutic effects of gamma knife irradiation on many neurological diseases, including drug resistance epilepsy.     

The bulbar network of respiratory neurons during apneusis induced by a blockade of NMDA receptors

Summary Our aim was to study the mechanisms producing the transition from the inspiratory phase to the expiratory phase of the breathing cycle. For this purpose we observed the changes affecting the discharge patterns and excitabilities of the different types of respiratory neurons within the respiratory network in cat medulla, after inducing an apneustic respiration with the N-methyl-D-aspartate (NMDA) antagonist MK-801 given systemically. Respiratory neurons were recorded extracellularly through the central barrel of multibarrelled electrodes, in the ventral respiratory area of pentobarbital-anesthetized, vagotomized, paralyzed and ventilated cats. Inhibitions exerted on each neuron by the presynaptic pools of respiratory neurons were revealed when the neuron was depolarized by an iontophoretic application of the excitatory amino-acid analogue quisqualate. Cycle-triggered time histograms of the spontaneous and quisqualate-increased discharge of respiratory neurons were constructed in eupnea and in apneusis induced with MK-801. During apneustic breathing, the activity of the respiratory neuronal network changed throughout the entire respiratory cycle including the post-inspiratory phase, and the peak discharge rates of all types of respiratory neurons, except the late-expiratory type, decreased. During apneusis, the activity of the post-inspiratory neuronal pool, the post-inspiratory depression of other respiratory neurons, and the phrenic nerve after-discharge were reduced (but not totally suppressed), whereas the discharge of some post-inspiratory neurons shifted into the apneustic plateau. The shortened post-inspiration (stage 1 of expiration) altered the organization of the expiratory phase. Late-expiratory neurons (stage 2 of expiration) discharged earlier in expiration and their discharge rate increased. The inspiratory on-switching was functionally unaffected. Early inspiratory neurons of the decrementing type retained a decrementing pattern followed by a reduced discharge rate in the apneustic plateau, whereas early-inspiratory neurons of the constant type maintained a high discharge rate throughout the apneustic plateau. Inspiratory augmenting neurons, late-inspiratory and offswitch neurons also discharged throughout the apneustic plateau. During the apneustic plateau, the level of activity was constant in the phrenic nerve and in inspiratory neurons of the early-constant, augmenting, and late types. However, progressive changes in the activity of other neuronal types demonstrated the evolving state of the respiratory network in the plateau phase. There was a slowed but continued decrease of the activity of early-inspiratory decrementing neurons, accompanied by an increasing activity and/or excitability of off-switch, postinspiratory and late-expiratory neurons. In apneusis there was a decoupling of the duration of inspiration and expiration. The variability of inspiratory duration increased five-fold whereas the variability of expiration was unchanged. We conclude that in the apneustic state, (1) inspiratory on-switching and the successive activation of the different inspiratory neuronal types are preserved; (2) near the end of the inspiratory ramp, the reversible phase of inspiratory off-switching is prolonged, producing the apneustic plateau, and (3) the irreversible phase of offswitching is impaired by a reduced activity of postinspiratory neurons. These results support the 3-phase model of respiratory rhythm generation, in which key roles are played by early-inspiratory and post-inspiratory neurons.     

Abnormal expression of cdk5 in focal cortical dysplasia in humans

Focal cortical dysplasia (FCD) is an important cause of refractory epilepsy in humans. The origin of its pathognomonic abnormal cell types and the links between abnormal cell morphology and epileptogenicity remain unknown. The developmentally-regulated kinase cdk5 and its neuronal activator p35 are known to be central to a number of key components in neuronal development, cellular morphology, cytoskeletal function, synaptic plasticity and neurodegeneration. Here we examine eight cases of human FCD for expression of cdk5. We show abnormal cdk5 immunoreactivity and aggregation of protein suggesting alterations in cdk5 may also be involved in this important epileptogenic human pathology.     

胚胎期铅暴露对斑马鱼胚胎及幼鱼NMDA受体mRNA表达的影响

目的:了解胚胎期铅暴露对斑马鱼胚胎及幼鱼N-甲基-D-天冬氨酸(NMDA)受体mRNA表达的影响。方法:野生型AB品系斑马鱼胚胎醋酸铅暴露浓度分别为0、0.1、0.5、2.5和12.5 μmol/L,提取各组受精后24、48、72、96和120 h(hpf)斑马鱼胚胎或幼鱼总RNA,实时定量PCR检测NMDA受体亚基NR1.1、NR1.2和NR2B的mRNA表达量。结果:(1)对照组NR1.1和NR1.2及NR2B表达量在胚胎发育过程中逐渐升高,在孵化期(72 hpf)表达量增加明显,在幼鱼早期(96 hpf)时达到高峰(与24 hpf时比较, P<0.01),在120 hpf时仍处于较高水平。(2)随着铅暴露浓度增高,NR1.1表达量增加并有高峰前移的趋势,2.5 μmol/L和12.5 μmol/L铅暴露组NR1.1表达高峰期在72 hpf,并且显著高于对照组(P<0.05);铅暴露组NR1.2和NR2B动态表达也呈类似规律,但NR1.2表达高峰期呈平台化趋势,横跨72 hpf至120 hpf阶段,NR2B表达高峰期出现在72 hpf和120 hpf阶段。(3)NR1.1、NR1.2及NR2B mRNA表达量之间Pearson相关系数值分别为r_NR1.1-1.2 =0.681、r_NR1.1-2B=0.637和r_NR1.2-2B =0.514,均有统计学意义(P<0.01)。结论:在斑马鱼胚胎发育过程NR1.1、NR1.2及NR2B mRNA表达水平逐渐升高,在幼鱼早期达到高峰;胚胎和幼鱼阶段NR1.1、NR1.2及NR2B之间mRNA表达水平存在关联;铅有上调NR1.1、NR1.2和NR2B mRNA表达作用并使表达峰期前移,改变了正常的NMDA受体表达规律。     

Differential expression of NMDA receptors in serotonergic and/or GABAergic neurons in the midbrain periaqueductal gray of the mouse

N-methyl-d-aspartate (NMDA) receptors expressed in the midbrain periaqueductal gray (PAG) exert various physiological functions. The PAG contains various neurotransmitter phenotypes, which include GABAergic neurons and serotonergic neurons. In the present experiments, we made tight-seal whole-cell recordings from GABAergic and/or serotonergic neurons in mouse PAG slices and analyzed NMDA and non-NMDA receptor-mediated excitatory postsynaptic currents (EPSCs) evoked by electrical stimulation. The NMDA/non-NMDA ratio of EPSC amplitude was high and the decay time course of NMDA-EPSC was slow in non-serotonergic/GABAergic neurons. In contrast, serotonergic neurons exhibited a low NMDA/non-NMDA ratio and a fast decay time course of NMDA-EPSC. Peripheral nerve ligation-induced chronic pain was associated with an increased NMDA/non-NMDA ratio in serotonergic neurons. Additionally, single-cell real-time RT-PCR analysis showed that peripheral nerve ligation up-regulated NR2B subunit expression in non-serotonergic/non-GABAergic neurons. Such changes in NMDA receptor expression in the PAG result in an alteration of the descending modulation of nociception, which might be an underlying mechanism for peripheral nerve injury-evoked persistent pain. Finally, the expression of NMDA receptors seems differentially regulated among neurons of different neurotransmitter phenotypes in the PAG.