Bilateral dorsal root potentials in the lower sacral spinal cord

Summary Bilateral dorsal root potentials (DRPs) evoked in the S3 dorsal roots by stimulation of the S2 and L6 dorsal roots and the cutaneous afferents entering the spinal cord in the lumbar segments have been studied in spinal cats. Stimulation of all these afferents produces DRPs which have the same amplitude on both sides of the spinal cord. During longlasting repetitive stimulation the negativity of the ipsilateral dorsal root is maintained only when this stimulation is applied to the neighbouring dorsal root. Depression of the testing DRPs produced by preceding single volleys or repetitive stimulation is only slightly larger on the contralateral side of the cord. The difference between depression of the DRPs on both sides of the cord is significantly smaller in the S3 than in the L7 segment. Following conditioning tetanization both ipsi- and contralateral DRPs undergo depression. The pattern of bilateral DRPs in the S3 segment significantly differs from that observed in the L7 segment and these differences correspond to the already known distinct arrangement of the substantia gelatinosa in the two parts of the cord.     

大鼠坐骨神经受压和解压后背根节和脊髓内神经元nNOS表达的变化

目的 :观察坐骨神经受压及解压后大鼠腰段背根节和脊髓内神经元型一氧化氮合酶 (nNOS)表达的变化 ,借以探讨外周神经源性痛的发病和影响机制。方法 :大鼠随机分为压迫组、解压组和对照组 ,采用聚乙烯管压迫坐骨神经的动物模型 ,用免疫细胞化学方法并结合计算机图像分析进行研究。结果 :与对照组比较 ,压迫组和解压组腰4～ 6背根节中nNOS的表达显著增加 ,相应节段脊髓背角的表达则明显降低 ;解压组与压迫组比较 ,背根节中nNOS的表达明显减少 ,而脊髓背角的已经下调的nNOS表达则回升 ,但仍然低于对照组水平。结论 :NO可能与神经源性痛时在中枢和外周的痛觉敏感性形成和神经系统长时程改变有关。     

Heterosynaptic modulation of the dorsal root potential in the turtle spinal cord in vitro

In the somatosensory system, the flow of sensory information is regulated at early stages by presynaptic inhibition. Recent findings have shown that the mechanisms generating the primary afferent depolarization (PAD) associated with presynaptic inhibition are complex, with some components mediated by a non-spiking mechanism. How sensory inputs carried by neighbouring afferent fibres interact to regulate the generation of PAD, and thus presynaptic inhibition, is poorly known. Here, we investigated the interaction between neighbouring primary afferents for the generation of PAD in an in vitro preparation of the turtle spinal cord. To monitor PAD we recorded the dorsal root potential (DRP), while the simultaneous cord dorsum potential (CDP) was recorded to assess the population postsynaptic response. We found that the DRP and the CDP evoked by a primary afferent test stimulus was greatly reduced by a conditioning activation of neighbouring primary afferents. This depression had early and late components, mediated in part by GABA_A and GABA_B receptors, since they were reduced by bicuculline and SCH 50911 respectively. However, with the selective stimulation of C and Aδ fibres in the presence of TTX, the early and late depression of the DRP was replaced by facilitation of the GABAergic and glutamatergic components of the TTX-resistant DRP. Our findings suggest a subtle lateral excitatory interaction between primary afferents for the generation of PAD mediated by a non-spiking mechanism that may contribute to shaping of information transmitted by C and Aδ fibres in a spatially confined scale in analogy with the retina and olfactory bulb.     

神经营养因子-3对大鼠脊髓半横断后背根神经节c-Jun表达的影响

目的：研究神经营养因子-3(NT-3)对脊髓半横断后背根神经节c-Jun表达的影响,探索NT-3促进脊髓修复的作用机制。方法：将实验动物分为：对照组,损伤组和NT-3注射组,应用荧光免疫组化法结合激光扫描共聚焦显微镜,观察各组背根神经节c-Jun的表达,并计数细胞核完整的神经元数目。结果：脊髓损伤后,背根神经节的细胞内c-Jun的表达上调;NT-3注射组脊髓损伤侧背根神经节神经元的c-Jun表达明显上调,背根神经节内细胞核呈完整状态的神经元数量明显增多。结论：(1)c-Jun在轴突损伤后表达上调。(2)NT-3对轴突损伤后的神经元有保护作用。(3)NT-3可能通过使c-Jun表达上调而发挥其促神经再生作用。     

Electron microscopic identification of postsynaptic dorsal root terminals: a possible substrate of dorsal root potentials in the frog spinal cord

Summary Dorsal root fibers were labeled with cobaltous chloride iontophoresis for electron microscopic investigations. In the base of the dorsal horn, where most of the coarser collaterals of dorsal root fibers terminate, many dorsal root terminals were found in postsynaptic relation to synapsing profiles. According to their morphological characteristics, three kinds of presynaptic terminals could be discerned in these complex synapses: axon terminals with spheric vesicles, axon terminals with flattered vesicles and presynaptic dendrites. These latter terminals contained relatively few flattened vesicles accumulated adjacent to a short synaptic articulation surface, and they were rich in cytoplasmic organelles. The functional significance of these structural specializations in the mediation of dorsal root potentials and recurrent inhibition is discussed.     

The effects of gallamine on field and dorsal root potentials produced by antidromic stimulation of motor fibres in the frog spinal cord

Summary The effects of gallamine on the intraspinal field potentials and the dorsal root potentials produced by antidromic stimulation of motor fibres were studied in the isolated frog spinal cord preparation. After gallamine (10^-3 M), the duration of the negative field potential produced by antidromic activation of motoneurons (N₁ response) was increased often without changing its amplitude. This resulted in an increased passive spread of the antidromic action potential towards the dorsal dendritic regions, where afferent fibres terminate.In the untreated spinal cord, stimulation of motor axons produced a late negative dorsal root potential (VR-DRP) which was depressed after gallamine administration. Abolition of the VR-DRP was frequently associated with the appearance of a short latency, conducted response, in the dorsal roots (EVR-DRP). The earliest component of the EVR-DRP had a latency ranging between 0.5 and 2.5 ms measured after the peak of the N₁ response recorded at the motor nucleus. Such a brief latency of the EVR-DRP suggests that this response results from electrical interaction between motoneurons and afferent fibres. After gallamine, the primary afferent depolarization produced by orthodromic stimulation of sensory nerves facilitates the EVR-DRP without necessarily increasing the amplitude or duration of the N₁ response. Also, gallamine appears to increase directly the excitability of the afferent fibre terminal arborizations.The nature of the electrical interaction between motoneuron dendrites and afferent fibre terminal arborizations is discussed in terms of two hypotheses: interaction by current flows and by electrical coupling.     

T-激肽原在大鼠腰骶髓及背根节的分布

目的 探讨T-激肽原在神经系统的定位及作用.方法 应用免疫细胞化学方法,结合光镜观察.本实验研究了T-激肽原在大鼠腰骶髓及L_(4-6)背根节的分布.结果T-激肽原分布于L_(4-6)背根节及腰骶髓灰质的第Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅸ层神经元及脊髓白质的神经胶质细胞和神经纤维.结论 在上述部位的神经元和神经胶质细胞,T-激肽原和高分子量激肽原、低分子量激肽原及其代谢产物可能共存.     

Effects of picrotoxin on potassium accumulation and dorsal root potentials in the frog spinal cord.

The effects of picrotoxin on the changes of extracellular potassium concentration (Δ[K⁺]_e), field potentials and dorsal root potentials evoked by afferent stimulation, were studied in the isolated spinal cord of the frog. Δ[K⁺]_e was measured with potassium selective micro-electrodes. In a normal Ringer's solution the Δ[K⁺]_e evoked by a single pulse applied to a dorsal root did not exceed 0.05 mM. In solutions containing picrotoxin (10^?7?10^?5m) the Δ[K⁺]_e increased to 0.06–0.1 mm. At higher concentrations (10^?4?10^?3m) of picrotoxin the Δ[K⁺]_e reached 3–6 mm and spontaneous elevations of [K⁺]_e were observed synchronously with the dorsal root potentials. The latter were depressed by 20–40% and considerably prolonged. The time constant of their ascending phase increased from 9 to 10 ms to 30–40 ms. The second component of the negative field potential, recorded from the intermediate region, increased and its time course corresponded to that of the evoked dorsal root potentials. Impulse activity of motoneurones and interneurones evoked by afferent stimulation was greatly enhanced. Picrotoxin (10^?4?5.10^?4m) was found to have no effect on the ‘asynaptic’ component of evoked dorsal root potentials, which is resistant to 20 mm MgSO₄ and to the absence of Ca²⁺. It is therefore unlikely that the depressant effect of picrotoxin on the evoked dorsal root potentials is produced by its direct action on the potassium conductance of primary afferents.The findings are consistent with a dual mechanism of dorsal root potentials. The fast component of evoked dorsal root potentials which is depressed by picrotoxin is apparently produced by activation of axo-axonic synapses at the primary afferents, while the slow component is due to transient accumulation of extracellular K⁺. The potassium component of the evoked dorsal root potentials becomes dominant in solutions with high concentrations of picrotoxin (10^?4?10^?3m) when impulse transmission is greatly enhanced.     

人胎儿和新生儿脊髓和DRG内nNOS阳性神经元的表达和分布

目的：观察24～27w人胎儿和新生儿的脊髓和背根神经节(DRG)内神经元型一氧化氮合酶(nNOS)阳性神经元的表达和分布。方法：ABC免疫细胞化学方法。结果：(1)24～27w人胎儿胸髓和腰1～3节段的中间带外侧核和前角Ⅷ层和Ⅸ层内可观察到nNOS阳性神经元。颈、胸、腰各段DRG内nNOS免疫阳性神经元占DRG细胞总数的84％～88％。(2)新生儿脊髓和DRG内nNOS免疫阳性神经元的分布情况与上述胎儿相似。但DRG内nNOS免疫阳性神经元的体积有所增加,数量明显减少,约占DRG细胞总数的70％～73％。结论：人胎儿脊髓和DRG在发育的24～27w至出生时,nNOS阳性神经元的表达在定位分布上无差异,但随胚胎发育阳性神经元的数量明显减少。     

Longitudinal extent of dorsal root fibres in the spinal cord and brain stem of the frog

The longitudinal arrangement of dorsal root fibres was investigated with a modified cobalt labelling technique in the spinal cord and brain stem of frogs. The topographical order of dorsal root fibres in the dorsal white column closely resembles the well-known scheme of the mammalian spinal cord. A significant difference between frogs and mammals is the extension of fibres up to the cerebellar plate. The ascending fibres of different origin are organized in concentric rings in the medulla. An oval-shaped area and a triangular area in the dorsal horn, and the motor horn, receive fibre collaterals in the spinal cord. Thoracic dorsal root fibres terminate exclusively in the oval-shaped area. Fibre terminations clearly outline the dorsal column nuclei which begin in the obex region and end at the level of the glossopharyngeal nucleus. The spinal nucleus of the trigeminus is richly supplied by both thin and thick calibre dorsal root fibres in its entire rostrocaudal extension. Two parts of the reticular formation receive dorsal root fibres; the first is in the dorsal gray matter ventral and lateral to the solitary fascicle in the medulla, the second is the lateral reticular zone. In the vestibular region, the medial, lateral and superior vestibular nuclei are innervated by dorsal root fibres. The granular layer of the cerebellum receives a significant contingent of dorsal root fibres. Fibres terminating in the vestibular region and in the cerebellum arise from limb-innervating spinal ganglia.The results indicate a close similarity in the longitudinal arrangement of dorsal root fibres in frogs and in higher vertebrates. The several collaterals that terminate in the hindbrain may modulate the function of the receiving structures. On the basis of present and previous findings the aggregation of primary sensory fibres and the convergence of their terminations are surveyed in the hindbrain.     

Anatomical relationship and positions of the lumbar and sacral segments of the spinal cord according to the vertebral bodies and the spinal roots

Segments of the spinal cord generally do not correspond to the respective vertebral level and there are many anatomical variations in terms of the segment and the level of vertebra. The aim of this study is to investigate the variations and levels of lumbar and sacral spinal cord segments with reference to the axilla of the T11, T12, and L1 spinal nerve roots and adjacent vertebrae. Morphometric measurements were made on 16 formalin fixed adult cadaveric spinal cords. We observed termination of the spinal cord between the axilla of the L1 and L2 spinal nerve roots in 15 specimens (93.8%). In all cadavers the emergence of the T11, T12, and the L1 spinal nerve roots was at the level of the lower one‐third of the same vertebral body. In 15 specimens (93.8%), the beginning of the lumbar spinal cord segment was found to be above the T11 spinal nerve root axilla and corresponded to the upper one‐third of the T11 vertebral body. The beginning of the sacral spinal cord segment occurred above the L1 spinal nerve root axilla and corresponded to the upper one‐third of the L1 vertebral body. The results of this study showed that when the conus medullaris is located at the L1–L2 level, the beginning of the lumbar spinal cord segment always corresponds to the body of T11 vertebra. This study provides detailed information about the correspondence of the spinal cord segments with reference to the axilla of the spinal nerve roots. Clin. Anat. 27:227–233, 2014. © 2013 Wiley Periodicals, Inc.     

Intersegmental synchronization of spontaneous activity of dorsal horn neurons in the cat spinal cord

Extracellular recordings of neuronal activity made in the lumbosacral spinal segments of the anesthetized cat have disclosed the existence of a set of neurons in Rexed's laminae III–VI that discharged in a highly synchronized manner during the occurrence of spontaneous negative cord dorsum potentials (nCDPs) and responded to stimulation of low-threshold cutaneous fibers (<1.5×T) with mono- and polysynaptic latencies. The cross-correlation between the spontaneous discharges of pairs of synchronic neurons was highest when they were close to each other, and decreased with increasing longitudinal separation. Simultaneous recordings of nCDPs from several segments in preparations with the peripheral nerves intact have disclosed the existence of synchronized spontaneous nCDPs in segments S1–L4. These potentials lasted between 25 and 70 ms and were usually larger in segments L7–L5, where they attained amplitudes between 50 and 150 μV. The transection of the intact ipsilateral hindlimb cutaneous and muscle nerves, or the section of the dorsal columns between the L5 and L6, or between the L6 and L7 segments in preparations with already transected nerves, had very small effects on the intersegmental synchronization of the spontaneous nCDPs and on the power spectra of the cord dorsum potentials recorded in the lumbosacral enlargement. In contrast, sectioning the ipsilateral dorsal horn and the dorsolateral funiculus at these segmental levels strongly decoupled the spontaneous nCDPs generated rostrally from those generated caudally to the lesion and reduced the magnitude of the power spectra throughout the whole frequency range. These results indicate that the lumbosacral intersegmental synchronization between the spontaneous nCDPs does not require sensory inputs and is most likely mediated by intra- and intersegmental connections. It is suggested that the occurrence of spontaneous synchronized nCDPs is due to the activation of tightly coupled arrays of neurons, each comprising one or several spinal segments. This system of neurons could be involved in the modulation of the information transmitted by cutaneous and muscle afferents to functionally related, but rostrocaudally distributed spinal interneurons and motoneurons, as well as in the selection of sensory inputs during the execution of voluntary movements or during locomotion. Electronic Publication     

电刺激排尿中圆锥部完全性骶部去传入的解剖学研究

目的:为从脊髓圆锥部进行完全性骶部去传入手术提供解剖基础。方法:解剖１０具成人脊柱脊髓标本,测量圆锥终末点至不同骶髓节段的距离。结果:脊髓圆锥长约３ｃｍ,位于Ｔ１２至Ｌ１椎体水平。从圆锥终末点Ｓ３和Ｓ２节段的长度分别为(１５．９±２．３)ｍｍ和(２１．６±２．７)ｍｍ。结论:在电刺激排尿时,切除圆锥终末背侧最远段２５ｍｍ的后根根丝,可完全切断Ｓ２及其以下的骶部传入纤维,获得彻底的膀胱去传入效果。     

胰岛素受体在猕猴腰段脊髓及相应背根神经节中的分布

目的:观察胰岛素受体在猕猴脊髓腰段第4~6(L4~L6)节段及相应节段背根神经节(dorsal root ganglion,DRG)中的形态学分布特点。方法:取1只成年猕猴的L4~L6节段脊髓并留取相应节段的DRG置于固定液中。脊髓冷冻水平切片(30μm)平均分为4组,分别行Nissl染色、荧光免疫组织化学染色、免疫组织化学染色和对照组处理,再于光学显微镜下观察;DRG平均分为2组,分别行免疫组织化学染色和对照组处理,再于光学显微镜下观察。结果:胰岛素受体分布于猕猴腰段脊髓L4~L6节段及相应节段的DRG中:(1)在腰段脊髓L4~L6节段,背角可见胰岛素受体阳性神经元胞体及终末,并大量分布于背角浅层(集中在第I、II层),腹角也可观察到散在胰岛素受体阳性神经元;(2)在L4~L6节段对应的DRG中,胰岛素受体阳性产物主要集中分布于中型(20μm直径≤40μm)、小型(直径≤20μm)神经元。结论:本研究为进一步研究灵长类动物脊髓和DRG中胰岛素受体的功能提供形态学依据。     

前列腺酸性磷酸酶在慢性痛大鼠脊髓背角和背根神经节的表达变化

目的:观察前列腺酸性磷酸酶(prostatic acid phosphatase,PAP)在多种慢性痛大鼠脊髓背角(spinaldorsal horn,SDH)和背根神经节(dorsal root ganglion,DRG)内的表达变化。方法:应用免疫组织化学染色法以及免疫荧光多重染色技术在多种慢性痛模型大鼠观察PAP的表达变化。结果:在正常大鼠,PAP阳性反应产物主要位于DRG的中、小型的非肽能神经元,PAP阳性神经元约占DRG神经元总数的64±4.3%;在脊髓背角,PAP阳性纤维和终末主要位于Ⅱ层。在神经病理性痛模型大鼠,术侧脊髓背角Ⅱ层的PAP阳性初级传入终末较对侧减少甚至消失,DRG内PAP阳性神经元较对侧明显减少。在慢性炎性痛模型大鼠,双侧脊髓背角和DRG内PAP的表达未见明显改变。结论:PAP特异地定位于DRG神经元以及脊髓背角Ⅱ层,可能与神经病理性痛信号的传递和加工密切相关。     

Galanin receptors and their second messengers in the lumbar dorsal spinal cord

The ligand binding properties of galanin receptors were examined in crude synaptosomal fraction preparations of lumbar dorsal spinal cord, using chloramin-T mono-iodinated porcine Tyr²⁶ galanin as ligand. The equilibrium binding of [¹²⁵I]galanin showed the presence of a single population of high-affinity binding sites with K_D= 0.6±0.2 nM in a concentration of 55±15 fmol mg^-1 protein (B_max. The N-terminal fragments galanin (1–16) and galanin (1–12) fully displaced specific [¹²⁵1]galanin binding from membranes with IC₅₀ values 6 nM and 4 μM, respectively. The C-terminal fragment galanin (17–29) did not displace [¹²⁵I]galanin when applied in the concentration range 10^-11–10^-4 M. GTP inhibited the specific binding of [¹²⁵I] galanin in a concentration dependent manner, with 54% inhibition at 1 mM, suggesting that the galanin receptor found in lumbar dorsal spinal cord is G-protein coupled. Second messenger systems, through which the galanin receptor in lumbar dorsal spinal cord may exert its effect, were also studied. A galanin (10,μm) produced inhibition (58%) of the depolarization induced cGMP increase was found, whereas galanin (10 μM) did not inhibit the noradrenalin (100 μM) activated CAMP synthesis or phosphoinositide turnover in tissue slices of the spinal cord. Bilateral transection of the sciatic nerve at midthigh level 14 days prior to the binding experiment was performed, a treatment which is known to cause a dramatic increase of galanin-like immunoreactivity in the superficial layers of the dorsal spinal cord, dorsal root ganglion and in galanin mRNA levels, but no significant effect on B_max or K_D of the galanin receptor was found.     

Nociceptive neurones in the superficial dorsal horn of cat lumbar spinal cord and their primary afferent inputs

Summary The morphology, background activity and responses to stimulation of primary afferent inputs of small neurones in the superficial dorsal horn which could only be excited from the skin by noxious stimulation were investigated by intracellular recording and ionophoresis of HRP. Neurones which gave similar responses to afferent stimulation were morphologically heterogeneous with respect to dendritic tree geometry and axonal projection, but were located around the lamina I/II border. Cutaneous excitatory receptive fields responding to noxious stimulation were generally small; most neurones had more extensive inhibitory fields responding to innocuous mechanical stimulation, in many cases overlapping the excitatory fields. Generally, stimulation of the excitatory field resulted in depolarization of the neurone and increased action potential firing, and stimulation of the inhibitory field resulted in hyperpolarization. Electrical stimulation of peripheral nerves revealed the existence of converging excitatory inputs carried by different fibre groups, and all neurones received an inhibitory input activated at low threshold. Excitatory responses were short-lived and occurred consistently in response to repeated stimulation. Central delay measurements gave evidence of a number of A monosynaptic inputs but only one A monosynaptic input; inhibitory inputs along A fibres were polysynaptic. The constant latency and regularity of the C response suggested monosynaptic connections. Low intensity stimulation of inhibitory inputs elicited a short-lived i.p.s.p. which increased in amplitude with increasing stimulus strength until it disappeared into a more prolonged hyperpolarization. This was associated with inhibition of background action potentials, and increased in duration with increasing stimulus strength up to C levels, indicating an A and C component. It is suggested that the level of excitability of these neurones depends on the relative amounts of concurrent noxious and innocuous stimulation, and that the resultant output, which is conveyed mainly to other neurones within the spinal cord, could modulate reflex action at the spinal level as well as affecting components of ascending sensory pathways.Supported by grant no. 11853/1.5 from the Wellcome Trust     

Projection field of primary afferent fibers innervating the ventral portion of the lumbar intervertebral disc in the spinal cord dorsal horn

In the present study, we investigated the central projection of afferent fibers innervating the lumbar intervertebral disc using the fluorescent neurotracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil). The tracer Dil was applied to the ventrolateral portion of the L5-L6 intervertebral disc in 11 adult rats. Fluorescent sites were observed microscopically on spinal cord transverse sections. Fluorescent spots in laminae I-III were plotted on the central projection map of cutaneous afferents. In six of 11 rats, Dil was restricted to the application site. Of these six rats, three showed no evident fluorescent sites. In the remaining three rats, small fluorescent spots were scattered in the dorsal horn. Fluorescent spots in dorsal horn lamina I were located in the central projection fields of the low back and groin skin. Fluorescent spots were observed, also sporadically, in Clarke's column in T12-L1 segments. The central projection of afferent fibers innervating the rat lumbar intervertebral disc was indistinct with Dil labeling. We presumed this was due to the scarcity of central terminal arbors of disc afferent fibers. Spotty projections in laminae I-IllIIere present near the central projection fields of the loin and groin, indicating that pain would be perceived in the groin.     

ClC-3在神经病理性痛大鼠脊髓背角及背根神经节的表达及其参与痛行为调控的研究

目的:观察电压门控性氯通道(voltage-gated chloride channel,ClC)3型在腓总神经结扎神经病理性痛模型大鼠脊髓背角(spinal dorsal horn,SDH)和背根神经节(dorsal root ganglion,DRG)内的表达变化及阻断氯离子通道后痛行为的改变。方法:应用免疫组织化学染色法、蛋白印迹法以及痛行为检测观察ClC-3在神经病理性痛大鼠SDH和DRG的变化和作用。结果:在正常大鼠,ClC-3主要位于DRG神经元胞膜;在SDH,ClC-3阳性纤维主要位于Ⅰ层。在腓总神经结扎大鼠,1周内结扎侧背角Ⅰ层及DRG的ClC-3表达增加,2～4周表达逐渐减少,在DRG也观察到相同的现象。给予氯离子通道阻断剂后,腓总神经结扎大鼠的痛阈下降。结论:ClC-3在神经病理性痛早期表达上调,随病程发展逐渐下降;阻断ClC-3可使大鼠痛阈下降。     

Chronic constriction injury induces aquaporin-2 expression in the dorsal root ganglia of rats

Aquaporins are a family of water channel proteins involved in water homeostasis in several tissues. Current knowledge of aquaporin expression in the nervous system is very limited. Therefore the first aim of this study was to assess, by immunohistochemistry and immunoblotting analysis, the presence and localization of aquaporin-2 in the spinal cord and dorsal root ganglia of naïve adult rats. In addition, we evaluated aquaporin-2 expression in response to chronic constriction injury of the sciatic nerve, a model of neuropathic pain. Our results showed that aquaporin-2 expression was not detectable either in the spinal cord or the dorsal root ganglia of naïve rats. However, we showed for the first time an increase of aquaporin-2 expression in response to chronic constriction injury treatment in small-diameter dorsal root ganglia neurons but no expression in the lumbar spinal cord. These data support the hypothesis that aquaporin-2 expression is involved in inflammatory neuropathic nerve injuries, although its precise role remains to be determined.