聚丙烯阴道无张力悬吊带对压力性尿失禁大鼠模型膀胱和尿道结构及功能的长期影响

目的：观察应用人工材料由内向外经闭孔阴道无张力吊带 (transobturator tension-free vaginal tape, TVT-O)治疗雌性大鼠压力性尿失禁模型的长期疗效，以及聚丙烯吊带对膀胱尿道结构功能的影响。 方法：实验于2006-06/2007-06在华北煤炭医学院动物中心实验室完成。选取青春期雌性SD大鼠24只，随机分为4组：①对照组只游离阴部神经，但不切断。②压力性尿失禁组、假手术组和TVT-O组行双侧阴部神经切断术建立压力性尿失禁模型。然后假手术组按TVT-O术操作，但不置入吊带；TVT-O组行标准的TVT-O术。于术后6周行腹压漏尿点压测定和膀胱测压。 结果：23只大鼠进入结果分析。①腹压漏尿点压：压力性尿失禁组低于对照组(P = 0.028)，TVT-O组恢复到对照组水平(P = 0.686)。②最大逼尿肌收缩压：各组比较差异无显著性意义(P > 0.05)。③膀胱容量：TVT-O组高于对照组和压力性尿失禁组(P < 0.05)。④膀胱顺应性：TVT-O组高于压力性尿失禁组(P < 0.05)。 结论：①应用人工合成材料聚丙烯吊带行TVT-O治疗大鼠压力性尿失禁安全、长期有效，不影响膀胱的收缩功能，但可以使膀胱容量和顺应性增加。②双侧阴部神经切断术可以建立长期稳定的压力性尿失禁大鼠模型。     

中成药天智颗粒对血管性痴呆大鼠脑内神经细胞增殖的影响

目的观察中成药天智颗粒对血管性痴呆大鼠学习记忆能力和神经前体细胞与星形胶质细胞增殖水平的影响。方法老年雄性SD大鼠192只,随机分为治疗组、模型组、假手术组和正常对照组,每组48只。治疗组、模型组采用双侧颈总动脉结扎方法建立血管性痴呆大鼠模型,于造模60d后治疗组大鼠应用天智颗粒5g/(kg·d)治疗30d。采用三等分Y型电迷宫测试各组大鼠的学习记忆能力,应用免疫组织化学尿嘧啶脱氧核苷(BrdU)和胶质纤维酸性蛋白(GFAP)染色方法标记并观察神经细胞增殖变化,以比较各组大鼠学习记忆能力和神经细胞增殖的变化规律和差异。结果与正常对照组相比,假手术组大鼠的学习记忆能力和免疫组织化学检测结果无明显变化。经天智颗粒治疗30d后,治疗组大鼠学习记忆能力明显改善,与模型组相比差异有统计学意义(P<0.05),BrdU阳性细胞显著增加(P<0.05),而星形胶质细胞明显减少(P<0.05);但与正常对照组相比,其学习记忆能力、BrdU阳性细胞和星形胶质细胞数量仍未恢复至正常水平(P<0.05)。结论天智颗粒可通过促进神经前体细胞的增殖而抑制星形胶质细胞的增殖,从而改善血管性痴呆大鼠的学习记忆能力。     

肛门失禁动物模型的造模方法

背景：各种类型人工肛门括约肌的出现,为肛门失禁开创出一条新的治疗途径,同时也存在许多不足之处,仍需要探索和改进。肛门失禁动物模型作为人工肛门体内实验研究的第一步,其重要性不容置疑。 目的：探讨一种新型肛门失禁动物模型造模方法的应用价值。 设计、时间及地点：随机对照动物实验,于2007-08/2008-06在广州南方医科大学附属南方医院动物实验中心完成。 材料：8月龄健康成年雄性新西兰兔30只,随机分为3组。 方法：对照组6只,局部注射药物为生理盐水,术后8周取局部组织做病理检查;罗哌卡因模型组12只,采用局部注射高浓度罗哌卡因的方法构建动物模型;乙醇模型组12只,采用局部注射体积分数为99%乙醇的方法构建动物模型。功能性定位双侧第4荐神经,神经周围注射药物。两组模型组分别于术后4和8周各取6只局部组织做病理检查。 主要观察指标：检测实验动物操作前后肛管内静息压力,计算操作前后肛管内静息压力的差值,观察肛门外括约肌及其双侧支配神经的神经肌电图和组织病理学变化。 结果：与对照组相比,模型组术后肛管内静息压力明显下降,第4荐神经无冲动传导;电镜扫描显示模型组术后神经变性严重,各模型组间无明显差别;神经周围组织病理结果显示,乙醇模型组纤维成分明显增多,少量炎症细胞浸润,其他组未见明显异常改变。 结论：局部注射神经毒性药物破坏肛门外括约肌双侧支配神经可成功制作出紧迫失禁的动物模型。注射高浓度罗哌卡因来制作紧迫性肛门失禁动物模型的方法,其短期造模效果确切,且创伤小,但在远期造模效果方面,仍需进一步的研究。注射体积分数为99%的乙醇来制作紧迫性肛门失禁动物模型的方法,其远期造模效果确切且稳定。 关键词：肛门失禁;疾病模型,动物;组织构建     

女贞子对大鼠脊髓损伤后细胞凋亡及Bcl-2、Bax的表达影响

目的 通过观察女贞子对大鼠脊髓损伤后细胞凋亡及Bcl-2、Bax表达的影响,探讨其对脊髓损伤的保护作用.方法 选用90只SD大鼠随机分为假手术组、模型组和治疗组,制成脊髓损伤动物模型.治疗组取女贞子液3.0 g/(kg·d)腹腔注射,假手术组与模型组取等量生理盐水腹腔注射,于各时间点制成脊髓切片,行苏木素一伊红(HE)...     

咬肌去神经对下颌骨发育影响的实验研究

目的 探讨咬肌去神经对大鼠下颌骨发育的影响.方法 24只28日龄雄性Wistar大鼠按随机数字表法分为手术组(n=9)、假手术组(n=9)、对照组(n=6),手术组切断大鼠右侧咬肌神经,假手术组仅解剖暴露出咬肌神经,不切除,对照组仅将大鼠麻醉.大鼠75日龄时行头颅CT平扫+三维重建,测量重建下颌骨相关线距;CT扫描完成后处死大鼠,切取双侧咬肌称其质量.结果 手术组大鼠手术侧咬肌质量小于非手术侧,差异有统计学意义(P<0.05);大鼠下颌骨长度Ⅰ、下颌骨长度Ⅱ、下颌骨长度Ⅲ、下颌骨高度Ⅰ 3组之间比较差异均无统计学意义(P>0.05);与对照组比较,手术组大鼠的下颌骨高度Ⅱ、下颌间距较低,手术组、假手术组大鼠的下颌骨高度Ⅲ较低,差异有统计学意义(P<0.05).结论 咬肌去神经使下颌骨高度Ⅱ和下颌间距减小,对下颌骨长度发育无明显影响.     

慢性脑供血不足大鼠脑中脑红蛋白的表达

目的 探讨慢性脑供血不足大鼠大脑皮质和纹状体中脑红蛋白的表达以及神经节苷脂GM1对其表达的影响。方法 24只大鼠随机分为3组：假手术组、慢性脑供血不足模型组、神经节苷脂GM1干预模型组，每组各8只。模型组通过结扎大鼠双侧颈总动脉建立慢性脑供血不足动物模型，模型建立8周后，GM1干预组每天腹腔注射GM130mg／kg，持续2周，应用免疫组化方法，观察脑组织中脑红蛋白的表达。假手术组只作双侧颈总动脉分离，不行血管结扎，其余步骤同模型组。结果 脑红蛋白主要表达于神经元中，在大脑中分布广泛。假手术组大鼠皮质和纹状体中有一定数量的脑红蛋白免疫反应阳性细胞，而慢性脑供血不足模型组较假手术组显著增多，GM1干预组较模型组进一步增加。结论 慢性脑供血不足后脑红蛋白的表达有部分代偿性提高，GM1可部分提高脑红蛋白的表达。     

双侧坐骨神经及股神经离断并固定大鼠神经肽Y水平对骨密度的影响

背景：以往研究认为,刺激坐骨神经及中枢神经受伤可使神经肽Y含量发生改变,神经肽Y对破骨细胞产生作用,影响骨代谢。 目的：验证双侧坐骨神经、股神经失神经及固定后神经肽物质对大鼠双侧胫骨骨密度的影响,并进行相关性分析。 设计、时间及地点：随机对照动物实验,于2006-09/11在湘南学院附属医院完成。 材料：10周龄SD雄性大鼠96只,体质量220~250 g,用于制备失神经支配模型。 方法：96只SD大鼠按数字表法随机分为3组,每组32只。①失神经支配组：切断大鼠两侧后肢坐骨神经和两侧股神经,远端游离5 mm,缝合切口。②固定组：大鼠切断神经,程序同前,继之采用管型石膏固定。③对照组：行假手术,仅暴露神经,然后缝合伤口。 主要观察指标：实验期间大鼠的一般情况。造模后1,10,30,60 d每组分别处死大鼠8只,观察双侧胫骨骨密度和神经肽Y的变化及神经肽Y水平与骨密度水平的相关性。 结果：96只SD大鼠均进入结果分析。①失神经后神经肽Y含量先降低,后升高,随着失神经支配时间的延长,神经肽Y持续升高,超过正常水平。②固定组神经肽Y含量先升高,后下降,但随着固定时间的延长,逐步升高并超过正常水平。③随着神经肽Y含量变化,大鼠双侧胫骨骨量也相应发生改变,大鼠失神经、固定30 d后双侧胫骨骨密度明显下降。失神经及固定后神经肽Y与骨密度含量变化高度相关(P < 0.01)。 结论：失神经支配及固定后大鼠神经肽Y含量变化均与骨密度改变具有高度相关,故可认为神经肽Y可作为骨质疏松形成的关键指标之一。     

脑出血偏瘫大鼠瘫肢正中神经不同时期的超微结构变化

目的观察脑出血大鼠瘫肢正中神经超微结构的变化。方法 Wistar大鼠60只,模型组及假手术各30只,通过胶原酶加肝素联合注射法建立大鼠脑出血动物模型。造模成功后第3天、14天分别分离瘫肢和健肢正中神经,活检、固定,切片、染色,观察正中神经镜下变化(光镜、电镜)。结果无论是模型组还是假手术祖,光镜下计数大鼠正中神经有髓神经髓鞘无明显变化。同时电镜下观察正中神经超微结构未发现有髓神经轴突肿胀、未出现髓鞘脱失、间质水肿等超微结构改变。结论脑出血偏瘫大鼠瘫肢周围神经结构无明显损害。     

脂肪来源神经干细胞移植局灶性脑缺血模型大鼠的血管新生

背景：脂肪组织来源的神经干细胞移植可改善脑缺血大鼠神经功能,但其机制尚不明确。 目的：观察人脂肪组织来源神经干细胞移植对大鼠局灶性脑缺血后血管新生的影响。 方法：体外培养脂肪基质细胞,诱导分化为神经干细胞。60只健康雄性SD大鼠分为4组：正常组6只,假手术组6只,缺血对照组24只,移植治疗组24只。后两组线栓法制作大鼠大脑中动脉缺血2 h再灌注模型,又分为缺血2 h再灌注7,14,21,28 d组,每个时点各6只。假手术组不闭塞大脑中动脉。造模成功后24 h,移植治疗组经尾静脉移植人脂肪组织来源神经干细胞悬液,细胞浓度为2×109 L-1;缺血对照组经尾静脉注射生理盐水。免疫组织化学法进行微血管密度计数,观察脑缺血区血管增生情况。 结果与结论：免疫组织化学结果显示,与缺血对照组比较,移植治疗组缺血2 h再灌注7,14,21,28 d的微血管密度值均显著高于缺血对照组,差异有显著性意义(P < 0.05~0.01)。提示脂肪组织来源的神经干细胞移植可促进脑缺血区新生血管的形成。     

金纳多对血管性痴呆大鼠认知功能及生长抑素表达的影响

目的研究金纳多对血管性痴呆(vascular dementia,VD)大鼠认知功能及生长抑素(SS)表达的影响。方法采用结扎双侧颈总动脉方法制备慢性前脑缺血动物模型。将100只老龄大鼠随机分为假手术组、模型组和金纳多组。应用水迷宫及免疫组化方法对各组大鼠学习记忆及SS表达进行观察。结果模型组与假手术组学习记忆能力差异有统计学意义(P<0.05);与模型组比较,金纳多治疗30 d后大鼠学习记忆能力明显改善(P<0.05),SS阳性神经元表达增加(P<0.05)。结论金纳多可增加SS阳性神经元表达,改善VD大鼠学习记忆能力。     

Human muscle-derived cell injection in a rat model of stress urinary incontinence

We investigated the use of human muscle-derived cells (hMDCs) for the treatment of stress urinary incontinence (SUI) in a nude rat model. hMDCs were isolated from adult skeletal muscle. Three groups of six animals consisting of controls, animals undergoing sciatic nerve transection (SNT) with periurethral sham-injection, and SNT with hMDCs (1 x 10(6) cells/20 microl saline) were utilized. Leak point pressure (LPP) was measured 4 weeks following injection. Bilateral SNT resulted in a significantly lower LPP that was significantly higher following hMDCs than sham injection. The results demonstrate the efficacy of human muscle cell therapy alone in improving physiologic outcomes in an animal model of SUI.     

Direct projections from the dorsolateral pontine tegmentum to pudendal motoneurons innervating the external urethral sphincter muscle in the rat

Direct projections from the dorsolateral pontine tegmentum to pudendal motoneurons innervating the external urethral sphincter and the external anal sphincter muscles were examined in the rat by the tract-tracing methods utilizing retrograde transport of cholera toxin B subunit and anterograde transport of biotinylated dextran amine. The dorsolateral pontine tegmental region, corresponding to the micturition reflex center of Barrington, was confirmed to send bilaterally, with an ipsilateral dominance, projection fibers to the spinal parasympathetic nucleus (inferior intermediolateral nucleus). The micturition reflex center of Barrington, however, did not seem to send many projection fibers to the ventral horn of the lumbosacral cord segments, whereas the region immediately ventral to the micturition reflex center of Barrington was found to send bilaterally, with a contralateral dominance, projection fibers to the dorsolateral group of pudendal motoneurons in both the male and female rats. In the female rat, the dorsolateral group of pudendal motoneurons are comprised primarily of motoneurons that innervate the external urethral sphincter muscle. The dorsomedial group of pudendal motoneurons, which contain motoneurons that innervate the external anal sphincter and the bulbocavernosus muscles, did not seem to receive major projections from the dorsolateral pontine tegmental regions. It was also observed that the locus coeruleus sent some projection fibers bilaterally to the spinal parasympathetic nucleus but only a few to the ventral horn of the lumbosacral cord segments. Thus, the present results indicate that the dorsolateral group of pudendal motoneurons containing those innervating the external urethral sphincter muscle receive pontospinal projection fibers mainly from the dorsolateral pontine tegmental region immediately ventral to the micturition reflex center of Barrington. © 1995 Wiley-Liss, Inc.     

Pattern of sensory innervation of the perineal skin in the female rat

Here we describe the nerves innervating the perineal skin together with their sensory fields in the adult female rat. Electrophysiological recording showed that the lumbosacral and L6-S1 trunks, in part by way of the sacral plexus, transmit sensory information from the perineal skin via four nerves: the viscerocutaneous branch of the pelvic nerve innervating the skin at the midline between the vaginal opening and anus, the sensory branch of the pudendal nerve innervating the clitoral sheath, the distal perineal branch of the pudendal nerve innervating a broad area of skin adjacent to the vaginal opening and anus, and the proximal perineal branch of the sacral plexus innervating a broad area of skin adjacent to the clitoris and vaginal opening. The sensory fields of three of these nerves overlapped to some degree: the viscerocutaneous branch of the pelvic and the distal perineal branch of the pudendal nerves at the midline skin between the vaginal opening and the anus, and the distal perineal branch of the pudendal nerve and the proximal perineal branch of the sacral plexus at the skin lateral to the vaginal opening. Such overlap might provide a safeguard helping to ensure that somatosensory input from the perineal region important for triggering reproductive and nonreproductive reflexes reaches the CNS.     

Dynamic change of proximal conduction in demyelinating neuropathies: a cervical magnetic stimulation combined with maximum voluntary contraction.

OBJECTIVE: To evaluate conduction abnormalities in the nerves innervating the proximal muscles in demyelinating neuropathies (DN) using cervical magnetic stimulation. METHODS: We applied cervical root magnetic stimulation in the biceps brachii muscles and examined its activity-dependent conduction changes produced by maximal voluntary contraction (MVC) in 12 DN patients (seven chronic inflammatory demyelinating polyradiculoneuropathy and five multifocal motor neuropathy), six motor neuron disease (MND) patients, and 12 healthy volunteers. RESULTS: Defining the upper normal limit of motor threshold (31%) and latency (6.7 ms) of the compound muscle action potential (CMAP) as mean+2SD, most DN patients revealed an abnormality in motor threshold (10/12) and latency (11/12) in contrast to MND patients (motor threshold (1/6) and latency (0/6)). These parameters contribute to the differentiation of DN from MND (P<0.01). Furthermore, the MVC maneuver transiently decreased the CMAP amplitude ratio (after MVC/before MVC x 100) in DN (83+/-18 %) compared with MND (P<0.01). Two of three DN patients who showed normal motor threshold or latency as in MND were successfully differentiated from MND by the MVC maneuver. CONCLUSIONS: In DN patients, conduction abnormality in the nerves innervating the proximal muscles was revealed by cervical magnetic stimulation combined with the MVC maneuver. SIGNIFICANCE: Our results suggested that conduction abnormalities in the proximal nerves innervating the proximal muscles could be evaluated by this method.     

单侧输尿管梗阻模型大鼠肾间质纤维化过程中血小板衍生生长因子D的表达

背景：血小板衍生生长因子在肾间质中通过诱导肾小管间质细胞增生、表型转化、炎性细胞浸润等导致肾小管间质纤维化。 目的：观察血小板衍生生长因子D在单侧输尿管梗阻模型大鼠肾脏组织中的表达水平及随时间的演变情况。 方法：将成年健康雄性SD大鼠60只随机分为模型组及假手术组,将模型组大鼠左侧输尿管结扎剪断建立单侧输尿管梗阻模型,假手术组大鼠不结扎剪断仅游离左侧输尿管。术后3,7,14,21,28 d,通过免疫组化检测血小板衍生生长因子D在肾脏组织中的表达分布情况,实时荧光定量RT-PCR方法检测血小板衍生生长因子D mRNA的表达水平及变化。 结果与结论：假手术组血小板衍生生长因子D仅少量表达于肾小球系膜细胞及血管平滑肌细胞,而在模型组,血小板衍生生长因子D同时表达于肾间质纤维化区域,随纤维化程度加重,表达增多。同时模型组血小板衍生生长因子D mRNA表达量较假手术组显著增多(P < 0.05),且表达随时间延长逐渐增多。提示血小板衍生生长因子D在单侧输尿管梗阻模型肾间质纤维化过程中发挥着促纤维化的重要意义。     

Gamma-Aminobutyric Acid-Inhibitory Motor Innervation of Leg Muscles of the Shore Crab

The inhibitory motor innervation of a crustacean leg was studied in the crab, Carcinus maenas. In in vitro preparations of the central nervous system and the proximal leg nerves, motor nerve recordings demonstrate the presence of a single common inhibitory motor neuron which elicits picrotoxin-sensitive inhibitory junction potentials in a distal leg muscle, the accessory flexor. This inhibitor is the common inhibitor (CI). Immunohistochemical detection of the inhibitory motor neuron neurotransmitter, gamma-aminobutyric acid (GABA), allows us to identify three immunoreactive motor neuron axons in sections of the distal leg nerves and of proximal leg nerves. One corresponds to the CI whereas the other two are the specific inhibitors, one to the stretcher and one to the opener muscles. After nickel chloride backfills of the CI in proximal leg nerves, GABA immunodetection fails and thus confirms that CI is the single inhibitor having branches in proximal leg nerves. These results demonstrate that the inhibitory motor innervation of a crab leg comprises three and only three inhibitors: the common inhibitor innervating all leg muscles and the two specific inhibitors, each innervating a single distal leg muscle. Further conclusions can be drawn: first, a muscle innervated by more than one excitatory axon has no specific inhibitor; second, sensory afferents are not mediated by GABA. Finally, during locomotion, the leg muscles receive two very distinct types of motor input: (1) one common to all the muscles coming from the common inhibitor which was previously shown by other authors to prevent build-up of tension in the muscles, thus allowing each muscle to contract according to (2) the specific motor input it receives from its own excitors.     

The absence of dystrophic characteristics in normal muscles successfully cross-reinnervated by nerves of dystrophic genotype: physiological and cytochemical study of crossed solei of normal and dystrophic parabiotic mice.

Dystrophic mice and normal littermates were joined in parabiotic union between 20 to 23 days of age with a cross of the “fast” tibial nerve of one partner to the slow soleus muscle of the other. This preparation allowed us (a) to monitor the “neurotrophic” influences of “fast” nerves on slow muscles and (b) to assess the influence of these nerves on the expression of hereditary muscular dystrophy. Twelve parabiotic pairs examined 3 to 6 months postoperatively reveal that the cross-reinnervated solei, either normal or dystrophic, exhibit post-tetanic potentiation, a mean 30% decrease in contraction time, and a mean 48% decrease in half-relaxation time as compared to the contralateral control muscles which were self-reinnervated. Self-reinnervated dystrophic solei generate 60% less tension than do self-reinnervated normal solei. The contractile capabilities of solei of the dystrophic mice cross-reinnervated by nerves of the normal partners are not enhanced, nor are these parameters reduced in normal solei receiving nerves of dystrophic genotype. Instead, cross-reinnervated solei exhibit twitch and tetanic tensions similar to those of their contralateral control muscles. Cytochemical and structural analyses indicate that the crossed “fast” nerves of normal or of dystrophic genotype are effective in altering the cytochemical pattern of the slow muscles to fiber types characteristic of fast muscles. However, normal nerves innervating solei of the dystrophic parabiont do not arrest the progress of the disease, and nerves of dystrophic genotype innervating muscles of the normal parabiont do not induce a pathological state. The results indicate that the peripheral motor nerves of dystrophic mice are normal in exerting “neurotrophic” influences and that muscular dystrophy progresses in spite of the presence of normal “neurotrophic” influences. This unique approach of a double nerve cross achieved through parabiosis gives strong evidence that the etiology of hereditary muscular dystrophy in this species is not nerve mediated.     

The organization of the motoneurons innervating the axial musculature of vertebrates. II. Florida water snakes (Nerodia fasciata pictiventris)

The motor pools of axial muscles in Florida water snakes (Nerodia fasciata pictiventris) were studied by applying horseradish peroxidase (HRP) to branches of spinal nerves innervating individual muscles or groups of muscles. Motor pools of different muscles or muscle groups were located in characteristic positions in both the transverse and the longitudinal extent of the motor column. Epaxial pools were located ventromedially in the column, segregated from most hypaxial ones, which were dorsolateral. The only exception to this general rule was the motoneurons innervating the levator costae muscle. Some of the motoneurons innervating this hypaxial muscle were located in the ventral part of the motor column, like epaxial motoneurons, but they were segregated longitudinally from epaxial ones. The arrangement of the motor pools was strikingly similar to the motor pools of presumptive homologous muscles in rats (Smith and Hollyday: J. Comp. Neurol. 220:29-43, '83), even though the locomotor mechanics in the two animals are very different. The similarities may reflect a comparable relationship between the location of motoneurons in the motor column and the location, in embryonic life, of the muscles they innervate. They also suggest that differences in the locomotor mechanics in the two species are accomplished without any dramatic reorganization of the medial motor column, in marked contrast to the substantial reorganization necessary to account for differences in the motor columns of amniotes and anamniotes.     

Organization of hindlimb nerve projections to the rat spinal cord: A choleragenoid horseradish peroxidase study

The aim of the present study has been to investigate the projections of hindlimb muscle afferent fibers to the spinal cord with particular emphasis on the ventral horn and the column of Clarke. Following transections of the appropriate ventral roots, injections of the B-subunit of cholera toxin conjugated to horseradish peroxidase were made into the tibial, peroneal, hamstring, superior gluteal, femoral, and obturator nerves in one group of adult rats. In another group of rats, similar experiments were done with intact ventral roots in order to map the location in the ventral horn of the motoneuron cell columns supplying each investigated nerve. An extensive overlap was found for the different nerve projections to Rexed's laminae V-VII. A somatotopic organization of the nerve projections was seen in the lamina IX cell groups of the ventral horn as well as in the column of Clarke, even though an overlap existed. The densest primary afferent projection from each injected nerve was to its homonymous motoneurons. Only a small to moderate overlap between the projections of the tributary branches of the sciatic nerve was found in the ventral horn, whereas the obturator and femoral nerve projections showed more profound overlap. In the column of Clarke, hindlimb nerves innervating distal muscles projected medially, and nerves innervating proximal muscles projected laterally. © 1996 Wiley-Liss, Inc.     

Accuracy of reinnervation of rat internal intercostal muscles by their own segmental nerves

The positions of internal intercostal motoneurons within their motor pool were studied, following reinnervation of the intercostal muscles by their original nerves. Six to 9 weeks after proximal nerve section in 10-d-old and adult rats, 0.1 microliter injections of wheat germ agglutinin (WGA)-HRP were made in the distal part of the reinnervated internal intercostal muscle. The corresponding region of the contralateral control muscle was also injected. The positions of the retrogradely labeled motoneurons were mapped in 100 microns transverse sections of thoracic spinal cord that had been stained for HRP according to the method of Mesulam (1982). In normal rats, motoneurons innervating distal muscle fibers are found largely in the more dorsal part of the internal intercostal motoneuron pool (Hardman and Brown, 1985). In adult rats, regenerated motor axons did not show any selectivity; distal muscle fibers were innervated by motoneurons whose cell bodies were distributed throughout the internal intercostal pool. However, in rats operated on at 10 d of age, distal intercostal muscle fibers were reinnervated by motoneurons that were distributed mainly in the dorsal part of the motor pool. These results support the view that positional signals may be of importance in organizing the distribution of axon terminals within muscles during development.