人工反射弧建立后大鼠膀胱胆碱能神经的形态学变化(英文)

目的观察体神经—内脏神经人工反射弧建立后,大鼠膀胱肌间神经丛分布的改变以及神经肌肉接头处的变化。方法Sprague-Dawley大鼠随机分为三组:对照组、脊髓横断组和手术重建组。手术重建组大鼠术后饲养3个月,与脊髓横断组大鼠一起进行脊髓横断,再继续饲养3个月,对照组不做任何处理。DiI进行逆行神经追踪;免疫荧光的方法显示DiI阳性标记细胞中的胆碱乙酰转移酶(choline acetyltransferase,ChAT);改良的Karnovsky-Roots法检测膀胱铺片中神经纤维的分布。结果DiI阳性标记细胞主要分布于脊髓L3尾部至L5头侧前角,ChAT阳性细胞和DiI阳性标记细胞部分重叠。手术重建组和对照组相比,膀胱肌间神经纤维的数量较少,染色浓度也较浅(P<0.05);而手术重建组神经纤维密度较脊髓横断组增大,染色浓度增强(P<0.05),且出现明显的神经再分布。结论人工体内脏神经反射弧建立后,新的传出支为体神经,可以长入副交感神经纤维,传出神经元的递质仍为乙酰胆碱,膀胱内胆碱能神经纤维再生和乙酰胆碱活性增强且出现神经再分布,这可能在膀胱的控制性排尿中起作用。     

神经生长因子及其结合肌基膜管移植修复脊髓横断性损伤的组织学观察

目的 对应用神经生长因子（ＮＧＦ）及其结合肌基膜管（ＭＢＬ）修复脊髓横断性损伤进行组织学评价。方法 横断雌性家犬脊髓后,分为三组：（Ａ）ＭＢＬ移植结合注射ＮＧＦ组７只。（Ｂ）脊髓单纯横断注射ＮＧＦ组６只。（Ｃ）对照组切除脊髓０．５ｃｍ４只。六个月后用免疫且化学方法对神经轴突和胶质细胞网络框架结构,进行特异染色,并用图像分析方法对脊髓横断处的远近端横截面进行神经纤维数量对比。结果 各组远端神经纤维数     

生物素标记葡聚糖胺神经束路示踪见证神经干细胞移植后皮质脊髓书的再生

实验旨在运用生物素标记葡聚糖胺神经束路示踪标记神经干细胞移植治疗脊髓损伤后皮质脊髓束的再生和神经的重新支配状况,结果表明神经干细胞移植治疗胸10脊髓横断损伤大鼠运动功能评分在横断损伤3周后逐渐升高。治疗后12周有部分生物素标记葡聚糖胺阳性标记的皮质脊髓束再生通过脊髓横断损伤部位,电镜检查发现再生的生物素标记葡聚糖胺阳性标记的神经终末与损伤远端神经元形成新的突触联系。说明生物素标记葡聚糖胺神经束路示踪能有效提供脊髓损伤后神经恢复的解剖形态学依据。     

高压氧预处理对大鼠急性脊髓损伤后神经细胞凋亡的影响

目的探讨高压氧预处理对急性脊髓损伤后不同时期神经细胞凋亡的影响及神经保护机制。方法将55只SD大鼠随机分为高压氧预处理组（25只）、正常损伤组（25只）及对照组（5只）。大鼠急性脊髓损伤模型制作采用改良Allen＇s法，分别于伤后1d、5d、7d、10d和14d在脊髓损伤部位取材，应用苏木精-伊红染色、原位缺口末端标记（TUNEL）方法检测大鼠脊髓损伤后的神经细胞凋亡情况。结果预处理组和单纯损伤组均见TUNEL阳性凋亡细胞，而预处理组凋亡细胞数减少；在各时间点预处理组与单纯损伤组差异均有统计学意义（P〈0．05）。结论高压氧预处理可减少继发性脊髓损伤细胞凋亡，因而可促进脊髓损伤后修复，对中枢神经系统损伤具有保护作用。     

脊髓损伤大鼠脊髓VRI表达及意义

目的了解脊髓损伤后逼尿肌反射亢进的原因。方法建立反射亢进型神经原性膀胱SD大鼠模型,于不同时间点取L4、L5、L6、S1脊髓节段,进行VRI免疫组化染色,观察各脊髓节段VRI表达。结果 VRI阳性表达局限于脊髓后角浅层（I层、Ⅱ层）的神经纤维,在模型组的表达高于对照组。结论脊髓损伤后脊髓中VRI表达增强可能是膀胱逼尿肌反射亢进的原因。     

局部注射骨髓间充质干细胞治疗大鼠脊髓损伤：运动功能有改善吗？

背景：目前研究多为骨髓间充质干细胞的体外培养及细胞移植对颅内疾病的治疗,对植入细胞在损伤脊髓中的成活、分化、迁移、结构重建等了解有限。 目的：探讨局部骨髓间充质干细胞移植在脊髓损伤修复中的作用和骨髓间充质干细胞替代治疗的可行性。 方法：成年健康雌性SD大鼠随机分为细胞移植组和对照组,建立SD大鼠脊髓横断损伤模型,伤后即刻分别向损伤区局部移植大鼠骨髓间充质干细胞悬液或无钙镁磷酸缓冲液。在术前和术后1 d,1周,2周,3周,4周和8周进行BBB评分,观测大鼠的运动功能,并于移植后1周免疫组织化学染色法观察BrdU标记的骨髓间充质干细胞在脊髓损伤处的存活情况,移植后4周进行损伤脊髓的大体观察和组织学检测。 结果与结论：移植后第1~8周细胞移植组BBB评分均髙于对照组;术后1周免疫组织化学染色结果显示在细胞移植组大鼠脊髓远端检测到BrdU阳性细胞,术后4周脊髓损伤处发现有神经纤维。证实通过损伤后立即局部注射的方式将骨髓间充质干细胞移植进大鼠脊髓损伤区,细胞可在损伤区存活;存活的骨髓间充质干细胞可分化为神经元,在损伤局部形成神经元通路,从而促进脊髓神经纤维传导功能的恢复,并促进高位脊髓损伤后大鼠后肢运动功能恢复。     

嗅黏膜嗅鞘细胞与肌基膜管联合移植修复脊髓损伤

目的：观察嗅黏膜来源的嗅鞘细胞与肌基膜管联合移植后对脊髓损伤的修复效果。 方法：1只SD大鼠行背正中切口，顺椎旁肌纤维切除约1.5 cm×0.8 cm×0.6 cm的肌条，复温、漂洗并挤压肌条以排出肌浆，制成肌基膜管。4只SD大鼠麻醉后取出嗅黏膜，胶原酶消化法分离培养嗅鞘细胞，调整浓度至1011 L-1。取SD大鼠50只，随机分成5组：嗅鞘细胞+肌基膜管联合组、嗅鞘细胞组、肌基膜管组、模型组、正常组，10只/组。除正常组外，其余组均建立脊髓损伤模型，于T10横断脊髓并切除约2 mm，将培养7 d的嗅鞘细胞与肌基膜管按组别分别植入脊髓断端，模型组用浸有DMEM的凝胶海绵桥接横断的脊髓。 结果：移植后第8周，嗅鞘细胞+肌基膜管联合组、嗅鞘细胞组大鼠运动功能明显恢复，出现大关节大幅度运动，且前者运动功能BBB评分升高尤为显著（P < 0.01）；肌基膜管组大鼠仅见小关节轻微活动；模型组大鼠后肢挛缩重，无明显功能恢复。嗅鞘细胞+肌基膜管联合组后肢体感诱发电位及运动诱发电位的潜伏期显著低于其他各组（P < 0.01）。苏木精-伊红染色和核转录因子免疫组化染色结果显示，嗅鞘细胞+肌基膜管联合组、嗅鞘细胞组的移植物与损伤脊髓整合较好，未见明显空洞，有大量染色呈阳性的纤维，纤维较长，由近侧端长入远侧端；肌基膜管组有空洞形成，染色阳性的纤维数量少，纤维细小且排列紊乱；模型组端断间充满瘢痕组织，未见明显染色阳性纤维。 结论：嗅鞘细胞移植可促进脊髓损伤后的轴突再生，肌基膜管作为一种生物管道，两者联合应用可明显促进脊髓损伤后的轴突再生及功能恢复。     

自体肋间神经联合酸性成纤维细胞生长因子移植治疗高位脊髓损伤

背景：酸性成纤维细胞生长因子具有调节细胞增殖、移行、分化和生存的作用,也可以下调已知轴突再生的抑制因子如蛋白聚糖等,帮助轴突克服这些抑制因子,对神经纤维再生有重要作用。 目的：观察酸性成纤维细胞生长因子联合周围神经移植治疗大鼠高位脊髓损伤的可行性及效果。 方法：健康成年雌性SD大鼠108只随机抽签法分为自体神经组、自体神经联合生长因子组、高位脊髓横断组。咬除大鼠T8~10棘突、椎板,显露硬膜囊,水平切断高位脊髓并切除3 mm,显微镜下确认无神经纤维相连。自体神经组、自体神经联合生长因子组取双侧第8~10对肋间神经各2 cm,将肋间神经交叉移植入高位脊髓缺损处(近端白质与远端灰质、远端白质与近端灰质),分别以纤维蛋白凝胶、含有酸性成纤维细胞生长因子的纤维蛋白凝胶固定植入的肋间神经,缝合硬膜。高位脊髓横断组断端间旷置。术后90 d,行体感诱发电位及运动诱发电位检测观察神经电生理恢复情况。术后76 d,生物素葡聚糖胺顺行神经示踪观察运动传导束恢复情况。术后60 d,后肢BBB运动功能评分观察肢体运动恢复情况。 结果与结论：高位脊髓横断组大鼠均未引出体感及运动诱发电位波形。自体神经组、自体神经联合生长因子组均可引出体感及运动诱发电位,自体神经联合生长因子组体感诱发电位及运动诱发电位的平均潜伏期和波幅、BBB评分均明显优自体神经组(P < 0.01)。自体神经组和自体神经联合生长因子组在损伤区有较多生物素葡聚糖胺标记阳性神经纤维通过,明显多于高位脊髓横断组(P < 0.01),自体神经联合生长因子组多于自体神经组(P < 0.01)。提示自体周围神经移植酸性成纤维细胞生长因子能更好地恢复高位脊髓损伤后大鼠肢体运动功能。     

大鼠脊髓损伤后PLGA支架细胞髓内移植的组织学观察

目的 观察神经干细胞(NSC)、许旺细胞(SCs)和组织工程材料乙交酯-丙交酯共聚物(PLGA)大鼠髓内共移植后的病理形态学改变.方法 36只Wistar大鼠,随机分为PLGA移植组、NSC/PLGA组和NSC+SCs/PLGA组.体外培养、鉴定胚胎脊髓源NSC和SCs,制备和构建PLGA支架细胞复合体并移植到大鼠脊髓Tq半横断损伤部位,应用HE染色、电镜和免疫组织化学染色方法在形态结构上观察材料的组织相容性、轴突髓鞘再生及NSC在脊髓内的存活、迁移和分化情况.结果 HE染色观察损伤12周时移植材料内可见细胞生长及新生的毛细血管;扫描电镜观察随着时间的延长,PLGA逐渐降解;材料正中横断面透射电镜观察可见新牛的无髓及有髓神经纤维;脊髓标本免疫组织化学染色可见移植的NSC可以在宿主脊髓内存活、迁移并分化成类神经元样细胞和少枝胶质细胞,未分化成星形胶质细胞.结论 NSC、SCs和PLGA共移植可以在形态学上促进大鼠脊髓半横断损伤的修复.     

神经干细胞与许旺细胞共移植于大鼠损伤脊髓

目的 观察神经干细胞与许旺细胞共移植于大鼠半横断脊髓损伤处神经干细胞的迁移、存活、分化及对损伤脊髓的修复作用.方法 绿色荧光蛋白(GFP)标记脊髓神经下细胞后与许旺细胞共移植于大鼠半横断脊髓损伤处,免疫荧光染色和电镜技术分别观察神经下细胞的迁移、存活、分化及新生的髓鞘.皮层运动诱发电位(CMEPs)及BBB评分分别检测大鼠运动功能的恢复.结果 在神经干细胞与许旺细胞共移植组,损伤脊髓的头端、尾端及对侧町见明显的GFP阳性细胞及GaLC/GFP、GFAP/GFP、NSE/GFP、SYN/GFP舣阳性细胞,电镜下新生的髓鞘最多,CMEPs恢复百分率和振幅明显高于其他两组,但BBB评分与神经干细胞单移植组差异无统计学意义.结论 神经干细胞和许旺细胞体内共移植可促进神经干细胞的辽移、存活、分化及脊髓运动功能的恢复.     

Botulinum toxin A modulates afferent fibers in neurogenic detrusor overactivity

Background: Although botulinum toxin (BoNT/A) injected into the detrusor muscle improves overactive bladder symptoms in patients with neurogenic detrusor overactivity, how it does so remains unclear. In this study, we investigated whether BoNT/A improves detrusor overactivity by modulating bladder afferent activity. Methods: To do so, during urodynamic assessment, we tested the soleus muscle Hoffmann (H) reflex during bladder filling before and after intradetrusor BoNT/A in patients with Parkinson’s disease (PD) and in patients with complete chronic spinal cord lesion (SCI) and detrusor overactivity refractory to conventional therapy. Healthy subjects underwent H reflex studies during urodynamic assessment and acted as controls. Results: Our findings show that BoNT/A injected into the detrusor muscle effectively reduces clinical overactive bladder symptoms in patients with PD and SCI. In healthy subjects and patients with PD, bladder filling [at maximum cystometric capacity, (MCC)] significantly decreased the H reflex size, whereas in patients with SCI, it slightly facilitated the H reflex size. At MCC, in patients with PD, BoNT/A significantly reduced the expected H reflex inhibition, whereas in those with SCI, BoNT/A turned the H reflex facilitation at maximum bladder filling into a slight inhibition. Conclusions: These findings show that BoNT/A injected into the detrusor muscle in patients with PD and SCI modulates bladder afferent activity. Modulation of bladder afferents possibly explains why BoNT/A improves detrusor overactivity.     

The Role of Vasoactive Intestinal Polypeptide and Pituitary Adenylate Cyclase-Activating Polypeptide in the Neural Pathways Controlling the Lower Urinary Tract

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are expressed in the neural pathways regulating the lower urinary tract. VIP-immunoreactivity (IR) is present in afferent and autonomic efferent neurons innervating the bladder and urethra, whereas PACAP-IR is present primarily in afferent neurons. Exogenously applied VIP relaxes bladder and urethral smooth muscle and excites parasympathetic neurons in bladder ganglia. PACAP relaxes bladder and urethral smooth muscle in some species (pig) but excites the smooth muscle in other species (mouse). Intrathecal administration of VIP in cats with an intact spinal cord suppresses reflex bladder activity, but intrathecal administration of VIP or PACAP in rats enhances bladder activity and suppresses urethral sphincter activity. PACAP has presynaptic facilitatory effects and direct excitatory effects on lumbosacral parasympathetic preganglionic neurons. Chronic spinal cord transection produces an expansion of VIP-IR (cats) and PACAP-IR (rats) in primary afferent axons in the lumbosacral spinal cord and unmasks spinal excitatory effects of VIP on bladder reflexes in cats. Intrathecal administration of PACAP6-38, a PAC1 receptor antagonist, reduces bladder hyperactivity in chronic spinal-cord-injured rats. These observations raise the possibility that VIP or PACAP have a role in the control of normal or abnormal voiding.     

Anatomical evidence for two spinal 'afferent-interneuron-efferent' reflex pathways involved in micturition in the rat: a 'pelvic nerve' reflex pathway and a 'sacrolumbar intersegmental' reflex pathway

We labeled interneurons in the L1-L2 and L6-S1 spinal cord segments of the rat that are involved in bladder innervation using transneuronal retrograde transport of pseudorabies virus (PRV) in normal animals and in animals with selected nerve transections. Preganglionic neurons were identified using antisera against choline acetyltransferase (ChAT). In some experiments we labelled parasympathetic preganglionic neurons (PPNs) in the L6-S1 spinal cord by retrograde transport of Fluorogold from the major pelvic ganglion. We identified bladder afferent terminals using the transganglionic transport of the anterograde tracer cholera toxin subunit b. We present anatomical evidence for two spinal pathways involved in innervation of the bladder. First, in the intact rat, afferent information from the bladder connects, via interneurons in L6-S1, to the PPNs that provide the efferent innervation of the bladder. The afferent terminals were located mainly in close apposition to interneurons located dorsal to the retrogradely labeled PPNs. Second, using L6-S1 ganglionectomies or L6-S1 ventral root rhizotomies we limited viral transport to the sympathetic pathways innervating the bladder. This procedure also labelled interneurons (but not PPNs) with PRV in the L6-S1 spinal cord in a location very similar to those described in the intact rat. These interneurons also receive bladder afferent terminals but we propose that they project to sympathetic preganglionic neurons, most of which are in the L1-L2 spinal segments. Based on this anatomical evidence, we propose the existence of two spinal reflex pathways involved in micturition: a pathway limited to a reflex arc in the pelvic nerve (presumably excitatory to the detrusor muscle); and a pathway involving the pelvic nerve and sympathetic nerve fibers, some of which may travel in the hypogastric (presumably inhibitory to the detrusor muscle).     

Degeneration of vagal efferent axons and terminals in cardiac ganglia of aged rats

Baroreflex control of the heart rate is significantly reduced during aging. However, neural mechanisms that underlie such a functional reduction are not fully understood. We injected the tracer DiI into the left nucleus ambiguus (NA), then used confocal microscopy and a Neurolucida Digitization System to examine qualitatively and quantitatively vagal efferent projections to cardiac ganglia of young adult (5-6 months) and aged (24-25 months) rats (Sprague Dawley). Fluoro-Gold was injected intraperitoneally to counterstain cardiac ganglionic principal neurons (PNs). In aged, as in young rats, NA axons projected to all cardiac ganglia and formed numerous basket endings around PNs in the hearts. However, significant structural changes were found in aged rats compared with young rats. Vagal efferent axons contained abnormally swollen axonal segments and exhibited reduced or even absent synaptic-like terminals around PNs, such that the numbers of vagal fibers and basket endings around PNs were substantially reduced (P < 0.01). Furthermore, synaptic-like varicose contacts of vagal cardiac axons with PNs were significantly reduced by approximately 50% (P < 0.01). These findings suggest that vagal efferents continue to maintain homeostatic control over the heart during aging. However, the marked morphological reorganization of vagal efferent axons and terminals in cardiac ganglia may represent the structural substrate for reduced vagal control of the heart rate and attenuated baroreflex function during aging.     

Anatomical evidence for two spinal ‘afferent–interneuron–efferent’ reflex pathways involved in micturition in the rat: a ‘pelvic nerve’ reflex pathway and a ‘sacrolumbar intersegmental’ reflex pathway

We labeled interneurons in the L1–L2 and L6–S1 spinal cord segments of the rat that are involved in bladder innervation using transneuronal retrograde transport of pseudorabies virus (PRV) in normal animals and in animals with selected nerve transections. Preganglionic neurons were identified using antisera against choline acetyltransferase (ChAT). In some experiments we labelled parasympathetic preganglionic neurons (PPNs) in the L6–S1 spinal cord by retrograde transport of Fluorogold from the major pelvic ganglion. We identified bladder afferent terminals using the transganglionic transport of the anterograde tracer cholera toxin subunit b. We present anatomical evidence for two spinal pathways involved in innervation of the bladder. First, in the intact rat, afferent information from the bladder connects, via interneurons in L6–S1, to the PPNs that provide the efferent innervation of the bladder. The afferent terminals were located mainly in close apposition to interneurons located dorsal to the retrogradely labeled PPNs. Second, using L6–S1 ganglionectomies or L6–S1 ventral root rhizotomies we limited viral transport to the sympathetic pathways innervating the bladder. This procedure also labelled interneurons (but not PPNs) with PRV in the L6–S1 spinal cord in a location very similar to those described in the intact rat. These interneurons also receive bladder afferent terminals but we propose that they project to sympathetic preganglionic neurons, most of which are in the L1–L2 spinal segments. Based on this anatomical evidence, we propose the existence of two spinal reflex pathways involved in micturition: a pathway limited to a reflex arc in the pelvic nerve (presumably excitatory to the detrusor muscle); and a pathway involving the pelvic nerve and sympathetic nerve fibers, some of which may travel in the hypogastric (presumably inhibitory to the detrusor muscle).     

Mechanisms underlying the pathogenesis of urinary bladder instability - new perspectives for the treatment of reflex incontinence

The urine storage ability of the urinary bladder is markedly impaired following inflammation of the urinary bladder and spinal cord injury because of a hyperexcitability of micturition reflexes. Using two rat models of inflammation-induced bladder overactivity and detrusor hyper-reflexia following spinal cord injury we investigated changes in the neuronal pathways to the urinary bladder which may underlie the development of this instability. Our results suggest that among the factors involved in inflammation-induced bladder instability are significant changes in the expression of the neuropeptides substance P, calcitonin gene-related peptide and galanin at the primary afferent level, as well as of the enzyme neuronal nitric oxide synthase (nNOS) at the afferent and postganglionic efferent level. In the lumbar and sacral spinal cord nNOS-immunoreactivity was depleted from dorsal horn neurones in both cystitis and spinal cord injured rats and from preganglionic parasympathetic neurones after spinal cord injury. Distension of the bladder in chronically spinalized rats elicited c-Fos expression in a significantly greater number of neurones throughout the lumbar and sacral segments than in rats with an intact neuraxis. Thus, under pathological conditions rather complicated changes in the synthesis of neuropeptides and nNOS occur at the primary afferent, spinal cord and postganglionic efferent level that together control the activity of the urinary bladder. Further mechanisms like unmasking of silent synapses and axonal sprouting in the spinal cord might further contribute to an increase in activity in micturition reflex pathways. Local cooling of the dorsal spinal cord at the level L6/S1 with temperatures between 14 and 20 °C proved a simple technique to control the unstable bladder and restore continence in both inflammation-induced detrusor overactivity and detrusor hyperreflexia following spinal cord injury. The effects of cooling are probably the result of a blockade of synaptic transmission within the dorsal cord which eliminates neuronal overactivity. Thus, local spinal cord cooling could offer a new method to treat bladder instability and reflex incontinence.     

Mechanisms underlying the pathogenesis of urinary bladder instability - new perspectives for the treatment of reflex incontinence

The urine storage ability of the urinary bladder is markedly impaired following inflammation of the urinary bladder and spinal cord injury because of a hyperexcitability of micturition reflexes. Using two rat models of inflammation-induced bladder overactivity and detrusor hyper-reflexia following spinal cord injury we investigated changes in the neuronal pathways to the urinary bladder which may underlie the development of this instability. Our results suggest that among the factors involved in inflammation-induced bladder instability are significant changes in the expression of the neuropeptides substance P, calcitonin gene-related peptide and galanin at the primary afferent level, as well as of the enzyme neuronal nitric oxide synthase (nNOS) at the afferent and postganglionic efferent level. In the lumbar and sacral spinal cord nNOS-immunoreactivity was depleted from dorsal horn neurones in both cystitis and spinal cord injured rats and from preganglionic parasympathetic neurones after spinal cord injury. Distension of the bladder in chronically spinalized rats elicited c-Fos expression in a significantly greater number of neurones throughout the lumbar and sacral segments than in rats with an intact neuraxis. Thus, under pathological conditions rather complicated changes in the synthesis of neuropeptides and nNOS occur at the primary afferent, spinal cord and postganglionic efferent level that together control the activity of the urinary bladder. Further mechanisms like unmasking of silent synapses and axonal sprouting in the spinal cord might further contribute to an increase in activity in micturition reflex pathways. Local cooling of the dorsal spinal cord at the level L6/S1 with temperatures between 14 and 20 degrees C proved a simple technique to control the unstable bladder and restore continence in both inflammation-induced detrusor overactivity and detrusor hyperreflexia following spinal cord injury. The effects of cooling are probably the result of a blockade of synaptic transmission within the dorsal cord which eliminates neuronal overactivity. Thus, local spinal cord cooling could offer a new method to treat bladder instability and reflex incontinence.     

Location and completeness of reinnervation by two types of neurons at a single target: The feline muscle spindle

Muscle spindles from the tenuissimus muscle of the cat were examined microscopically to assess the precision and completeness of reinnervation of intrafusal muscle fibers by efferent and afferent neurons. Positions of motor and sensory nerve terminals were charted relative to the cross-sectional area enclosed by the outer capsule of the spindle. Profiles of nerve endings were measured for normally innervated and reinnervated spindles. The tenuissimus was deprivedof innervation by freezing its nerve, sometimes in conjunction with either spinal ganglion removal or ventral rhizotomy. Sensory and motor terminals occupied separate locales along the length of normal muscle spindles. Nerve terminals of efferent and afferent neurons were located in appropriate positions along the length of spindles when axons of both types of neurons regrew-together and when either category of axon regenerated alone. Precise reinnervation of muscle spindles occurred in spite of a diminished diameter of intrafusal fibers. Repopulation of the spindle with motor endings was less complete than that by sensory endings, based on the proportion and size of the regenerated terminals. We conclude that under optimal conditions for axonal regrowth, efferent and afferent neurons reinnervate their respective regions along intrafusal muscle fibers but motor lags sensory reinnervation within the spindle. The mechanism by which positional specificity happens during reinnervation of intrafusal fibers requires neither an interaction between terminals of the two types of neurons nor target cells of normal bulk. © 1993 Wiley-Liss, Inc.     

Morphological plasticity in efferent pathways to the urinary bladder of the rat following urethral obstruction

Partial urethral ligation in female Wistar rats produces changes in the neural control of the lower urinary tract including bladder hyperactivity and facilitation of a spinal micturition reflex pathway. To gain insight into the mechanisms underlying these changes, axonal tracing studies were conducted to examine the postganglionic efferent limb of the micturition reflex pathway which originates in the major pelvic ganglion (MPG). Forty microliters of the tracer Fluoro-Gold (4%) were injected into the right side of the bladder in urethral-obstructed (n = 10) and control (n = 4) rats 6 weeks after urethral ligation or sham surgery. As a control Fast blue (40 microliters, 5%) was injected into the colon to label neurons in the MPG innervating the intestine. Obstructed rats exhibited a 6-fold increase (p less than 0.001) in bladder weight (0.848 gm) compared to controls (0.148 gm). A significant increase (p less than 0.001) in the size of labeled bladder postganglionic neurons in the MPG was noted in obstructed rats (576.4 microns 2, n = 4) as compared to controls (299.6 microns 2). However, labeled, colon postganglionic neurons in the MPG in obstructed (312.9 microns 2) rats were not enlarged compared to controls (359.4 microns 2). Neuronal hypertrophy was not associated with a change in the number of labeled MPG neurons in control and obstructed groups.(ABSTRACT TRUNCATED AT 250 WORDS)