Modulation of CREB expression and phosphorylation in the rat nucleus accumbens during nicotine exposure and withdrawal

The nucleus accumbens region of the brain has been shown to play a role in reward and reinforcing mechanisms of drugs of abuse. To understand the molecular mechanisms of nicotine addiction, the present investigation examined the effects of acute and chronic nicotine treatment and its withdrawal on cAMP-responsive element binding (CREB) protein expression and phosphorylation (serine-133) in nucleus accumbens (NAc) structures of rats. it was found that acute treatment (1 and 18 hr of withdrawal) with nicotine had no effects on total creb and phosphorylated CREB (p-CREB) protein levels in shell or core structures of rat NAc. On the other hand, 18-hr withdrawal after chronic nicotine exposure produced significant reductions in the total CREB and p-CREB protein levels in the shell but not in core structures of nac. interestingly, nicotine withdrawal (1 hr) after chronic exposure maintained normal levels of total CREB and p-CREB protein levels in the shell and core structures of NAc. These results suggest the possibility that decreased CREB activity in the shell of NAc may be associated with abnormal reward mechanisms during nicotine withdrawal after chronic exposure.     

The contribution of cholinergic enzymes and acetylcholine from the lumbar sympathetic chain to the rat sciatic nerve

Summary This study was performed to investigate how much of the acetylcholine (ACh), cholineacetyltransferase (ChAT) and ACh-esterase (AChE) in the rat sciatic nerve originate from the somatic motor input and from the automatic sympathetic input, respectively. The somatic motor axons to the sciatic nerve were eliminated by surgical transsection of the spinal roots, (rhizotomy) and the autonomie component was removed by surgical resection of the lumber sympathetic chain bilateraly (sympathectomy). Also combined operations were performed.In intact (non-crushed) sciatic nerve rhizotomy caused a reduction in ACh content by 70%, in ChAT-activity by 55%, and in AChE-activity by 41%. Sympathectomy alone had very little influence on ACh and ChAT, but reduced AChE by 20%. After crushing the nerve 13 hours before sacrifice, all three substances accumulated proximal to the crush region as described previously. When compared to the control group, sympathectomy alone caused a reduction in accumulated amounts of AChE only, while ACh and ChAT accumulations were essentially unchanged. Rhizotomy alone caused a substantial reduction in accumulated amounts of all three substances, but most prominently in ACh and ChAT-amounts. After symphathectomy in combination with rhizotomy ACh-accumulations were very low, and enzyme activities were reduced more than in the group with rhizotomy alone. A certain amount of residual ChAT and AChE was present in the nerve, and the location of this is discussed. The fact that combined sympathectomy and rhizotomy lowered ACh accumulations significantly more than would be expected from the results after either operation alone is commented upon.The results thus indicate that the major part of ACh enzymes in rat sciatic nerve is located in somatic motor axons. Very little ACh and ChAT, but about 20% of the ACh E is confined to the sympathetic axons. Some extraneuronal enzyme appears to be present.     

Effect of spinal cord ischemia on axonal transport of cholinergic enzymes in rabbit sciatic nerve

The fast axonal transport of acetylcholinesterase (AChE) and the slow transport of choline acetyltransferase (ChAT) were measured by the stop-flow ligation technique in the sciatic nerve of rabbits 6 and 24 h after ischemia performed by the occlusion of the abdominal aorta which lasted 40 min. Activities of these enzymes were also measured in punched samples of the spinal cord (L5-6). Results were correlated with those obtained from the sham-operated control group. Six h after ischemia, its only apparent effect was a different distribution of accumulated enzymes in the central nerve segments. Twenty-four h after ischemia, the transport of AChE was markedly depressed; proximodistal accumulation decreased by 68%, whereas enzyme activity in the intact contralateral nerve and in the ventral horns of the spinal cord was preserved. No effect of ischemia on the retrograde axonal transport of AChE was observed in this experimental model. Cytoplasmic ChAT is much more susceptible to necrotic degeneration than membrane-bound AChE; 24 h after ischemia its activity decreased significantly in all investigated parts of the sciatic motoneurones but the rate of slow axonal transport did not seem to be affected.     

Axoplasmic transport of thioredoxin and thioredoxin reductase in rat sciatic nerve

Thioredoxin and thioredoxin reductase were localized immunohistochemically in the rat sciatic nerve by immunofluorescence using specific rabbit antisera. Both proteins showed strong immunoreactivity in the cytoplasm of Schwann cells and at the nodes of Ranvier. The axoplasm of myelinated axons also showed a low, evenly distributed immunoreactivity for both proteins. A single or double crush of the nerve caused accumulation of immunoreactivity in dilatated axons both proximally and distally to the crush for up to 8 h. Local cooling of the nerve or subepineural injection of either colchicine or vinblastine prevented the accumulation indicating a role of microtubules. The results showed that thioredoxin and thioredoxin reductase are synthesized in nerve cell bodies and rapidly transported in axons both in anterograde and retrograde directions.     

Axonal transport of substance P-like immunoreactivity in regenerating rat sciatic nerve

Anterograde axonal transport of substance P-like immunoreactivity (SPLI) decreases after injury (crush or resection) to rat sciatic nerve. If the axons regenerate a partial recovery of transport occurs. If regeneration is impeded the decrease in transport is more severe and prolonged. No changes in the proportion of mobile SPLI (31%) or transport velocity (10.0 mm/h) occur. The decrease in SPLI transport largely accounts for the decline in SPLI content which occurs in nerve following injury and probably reflects decreased cell body synthesis.     

Axonal transport of glycerophospholipids in regenerating sciatic nerve of the rat during aging

The effect of age upon the axoplasmic transport of glycerophospholipids has been studied using as a model the regenerating sciatic nerve of young (2-month-old), young adult (6-month-old), middle-aged (16-month-old), and aged (20-month-old) male rats. The right sciatic nerve was crushed 0.5 mm down the incisura ischiadica. Four and nine days after the lesion, a mixture of [2-3H] glycerol and [methyl-14C] choline was bilaterally injected into the spinal cord, at a level of the L4-L5 vertebrae. The animals were killed 18 hr after the isotope injection. Proximal and distal portions of crushed nerve and of contralateral sham-operated ones were dissected and consecutive 5-mm segments were subjected to lipid extraction and analysis. The findings of the present study are summarized as follows: (1) The accumulation of labeled lipid material axonally transported four days after nerve injury was mainly located at the crush site in young, young adult, middle-aged, and aged rats. The accumulation of both 3H-glycerolipids and 14C-choline phospholipids in postcrush segments was markedly higher for young and young adult than for aged rats, four and nine days after crush; (2) the average rate of axonal regeneration, determined between days 4 and 9 following crush injury was 3.6 and 4.2 mm/day for 2-month-old and 6-month-old rats, respectively; it decreased to the value of 2.5 mm/day for 16-20-month-old rats.     

Chronic bupropion attenuated the anhedonic component of nicotine withdrawal in rats via inhibition of dopamine reuptake in the nucleus accumbens shell

Bupropion, a dopamine reuptake inhibitor, is an effective therapy for smoking cessation, but the behavioral and neurochemical mechanisms mediating its antismoking properties are relatively unknown. To explore the hypothesis that bupropion ameliorates nicotine withdrawal partly by a dopamine-dependent mechanism, we investigated the effects of chronic bupropion on potassium-stimulated dopamine overflow in the nucleus accumbens shell in nicotine-withdrawing rats. We also assessed the effects of chronic bupropion on behavioral aspects of nicotine withdrawal measured by elevations in brain reward thresholds and somatic signs of withdrawal. Rats were treated with nicotine or saline for 7 days and then coadministration of bupropion or saline was initiated. After 14 days of coadministration of bupropion/saline and nicotine/saline, nicotine/saline administration was terminated, whereas bupropion/saline administration continued. These conditions mimic bupropion administration in human smokers. Cessation of nicotine administration in non-bupropion-treated rats elevated reward thresholds reflecting a reward deficit, increased somatic signs and diminished potassium-evoked dopamine overflow in the nucleus accumbens shell. Chronic bupropion lowered reward thresholds and increased potassium-evoked dopamine release regardless of previous nicotine exposure, possibly by inhibition of dopamine reuptake, and thus attenuated the anhedonic and neurochemical effects of nicotine withdrawal. Chronic bupropion blocked withdrawal-associated increased somatic signs. Finally, acute experimenter-administered nicotine enhanced brain reward function equally in all groups, indicating that bupropion does not alter the reward-facilitating effects of experimenter-administered nicotine. In conclusion, the bupropion-induced increase in extracellular dopamine in the nucleus accumbens shell may ameliorate the anhedonia associated with nicotine withdrawal, which in turn may facilitate smoking cessation.     

Chronic effect of nicotine on serotonin transporter mRNA in the raphe nucleus of rats: reversal by co-administration of bupropion

Aim:  Epidemiologic studies suggest the existence of a biological link between nicotine withdrawal and depression. To investigate the neuronal mechanisms of the precipitation of depression during smoking cessation, an animal model of nicotine withdrawal was used, and the expression of serotonin transporter (5HTT), abnormality of which is implicated in the pathogenesis of depression, was investigated. The effect of co-administration of bupropion, which has been clinically shown to ameliorate nicotine withdrawal symptoms, was also investigated in this model.
Methods:  Male Wistar rats were implanted with a minipump s.c., which delivered nicotine at a rate of 6 mg/kg per day for 12 days (days 1–12). Rats given chronic nicotine were killed on day 13, or 2 days after the removal of minipump (withdrawal day 2). In a separate experiment, bupropion (15 or 30 mg/kg per day) was injected into the nicotine infused rats on days 2–12. The expression of mRNA for 5HTT in the dorsal raphe was determined on in situ hybridization.
Results:  Chronic nicotine infusion resulted in the reduction of 5HTT mRNA expression, which lasted through withdrawal day 2. Co-administration of bupropion, however, significantly antagonized this reduction.
Conclusions:  Chronic nicotine infusion reduces the synthesis of 5HTT protein, which may consequently precipitate depression during nicotine withdrawal, but co-administration of bupropion may ameliorate withdrawal symptoms by counteracting nicotine's effect on 5HTT.     

Axonal transport of the voltage-dependent Na channel protein identified by its tetrodotoxin binding site in rat sciatic nerves

Na+ channels levels were measured in different segments of rat vagus and sciatic nerves by in vitro binding using a tritiated ethylene-diamine tetrodotoxin derivative ([3H]en-TTX). Binding sites were found to accumulate on both sides of a ligature tied on the sciatic nerve indicating an anterograde and retrograde axoplasmic transport of Na+ channels. Accumulation of Na+ channels at the ligature was time-dependent and appeared to occur through fast axoplasmic transport mechanisms. This accumulation on both sides of a ligature was also visualized by autoradiographic studies in longitudinal sections of sciatic nerves using [3H]en-TTX.     

Expression changes and bioinformatic analysis of Wallerian degeneration after sciatic nerve injury in rat

Wallerian degeneration (WD) remains an important research topic. Many genes are differentially expressed during the process of WD, but the precise mechanisms responsible for these differentiations are not completely understood. In this study, we used microarrays to analyze the expression changes of the distal nerve stump at 0, 1, 4, 7, 14, 21 and 28 days after sciatic nerve injury in rats. The data revealed 6 076 differentially-expressed genes, with 23 types of expression, specifically enriched in genes associated with nerve development and axonogenesis, cytokine biosynthesis, cell differentiation, cytokine/chemokine production, neuron differentiation, cytokinesis, phosphorylation and axon regeneration. Kyoto Encyclopedia of Genes and Genomes pathway analysis gave findings related mainly to the MAPK signaling pathway, the Jak-STAT signaling pathway, the cell cycle, cytokine-cytokine receptor interaction, the p53 signaling pathway and the Wnt signaling pathway. Some key factors were NGF, MAG, CNTF, CTNNA2, p53, JAK2, PLCB1, STAT3, BDNF, PRKC, collagen II, FGF, THBS4, TNC and c-Src, which were further validated by real-time quantitative PCR, Western blot, and immunohistochemistry. Our findings contribute to a better understanding of the functional analysis of differentially-expressed genes in WD and may shed light on the molecular mechanisms of nerve degeneration and regeneration.     

Axonal transport of α-bungarotoxin binding sites in rat sciatic nerve

[¹²⁵I]α-Bungarotoxin (α-BuTX) binding sites accumulate both proximal and distal to a ligature positioned around the sciatic nerve of rats. [¹²⁵I]α-BuTX binding sites, localized using quantitative receptor autoradiography, were found to accumulate at nerve ligatures at a relatively constant rate which suggests that they undergo both anterograde and retrograde axonal transport. [¹²⁵I]α-BuTX binding to sections of ligated sciatic nerve was saturable with apparent dissociation constants of 0.97 nM proximal and 0.53 nM distal to the ligature.d-Tubocurarine, nicotine, decamethonium and atropine displaced [¹²⁵I]α-BuTX from sciatic nerve sections with affinities comparable to those previously reported for the toxin binding component of rat brain. These data indicate that [¹²⁵I]α-BuTX binding sites pharmacologically similar to those of rat brain are transported in sciatic nerve. Axonally transported toxin binding sites may correspond to those previously localized to the plasma membrane of peripheral nerve axons and on the terminals of motor neurons.     

Nodes of ranvier above a neuroma in the rat sciatic nerve: Voltage clamp analysis and electron microscopy

Neuroma formation was induced in adult rat sciatic nerves and the animals were allowed to survive for 1-10 months. In 10 animals single large myelinated fibres from the nerve segment above the neuroma were subjected to voltage clamp analysis. Six animals were fixed by glutaraldehyde perfusion and nodes of Ranvier or large myelinated fibres above the neuroma were examined in the electron microscope (EM). Most fibres exhibited normal action potentials, but a few had a reduced excitability and small action potentials. Some fibres had increased membrane time constant and leak conductance and a markedly increased membrane capacitance. Most of the examined nodes of Ranvier exhibited abnormally large delayed K currents, which could be blocked with 4-aminopyridine (4-AP). The Na current was normal. In the EM most large cross-cut myelinated axons were markedly atrophic, particularly after long survival times. Evaginations from the paranodal region of these axons penetrated between the terminating paranodal myelin lamellae. The nodal axolemmal undercoating could be very prominent and in some cases the nodal axon was irregular. These findings show that large myelinated peripheral nerve fibres, which are chronically disconnected from their peripheral targets, exhibit specific structural and functional abnormalities of the nodes of Ranvier.     

The effect of chronic administration of C-amphetamine on regional changes in catecholamines in the rat brain

Changes in the dopamine, noradrenaline and dihydroxyphenylacetic acid (DOPAC) concentrations were determined in 6 regions of the rat brain following chronic amphetamine administration for 2 weeks and at intervals of up to 7 days after drug withdrawal. Chronic amphetamine administration caused pronounced stereotypy; following withdrawal the animals were behaviourally depressed for at least 7 days. The noradrenaline concentration of all brain areas investigated was decreased throughout most of the experimental period; only in the midbrain and the olfactory lobes did the noradrenaline concentration return to control values 7 days after drug withdrawal. In contrast, the dopamine concentration was raised in the midbrain, hippocampus, and olfactory lobes following drug administration but reduced in the striatum, brain stem, and amygdaloid cortex. Following amphetamine withdrawal, most of the brain areas showed a decrease in the dopamine concentration apart from the olfactory lobes which showed an increase and the midbrain and hippocampus which were largely unchanged. The concentrations of the intraneuronal metabolite DOPAC were decreased in most brain areas throughout the duration of the experiment, suggesting that the turnover of dopamine was decreased. These results are discussed with reference to the possible decreased activity in tyrosine hydroxylase both during drug treatment and after withdrawal.     

Effect of Chronic Nicotine Treatment and its Withdrawal on the Vasopressinergic System in Rats

We have studied the effect of chronic nicotine treatment and its withdrawal on the hypothalamo-neurohypophyseal Vasopressinergic system in male Sprague-Dawley rats. They were subcutaneously infused with low and high doses of nicotine, free base (0.6 and 6.0 mg/kg/day, respectively) for 28 days, via Alzet osmotic pumps. The studies were carried out immediately after the period of infusion and 1, 7, 14 and 28 (the latter in high dose only) days later. Basal, high K⁺-stimulated and total vasopressin release from the superfused neural lobes, the residual vasopressin content in the neural lobes, and hypothalamus and plasma vasopressin concentration were measured by radioimmunoassay. Treatment with the high dose of chronic nicotine alone decreased vasopressin content in and release from the neural lobe and its plasma concentration, but it did not change significantly the vasopressin content in the hypothalamus. A similar pattern of changes in vasopressin release and plasma concentration, though less pronounced, was observed in the rats infused with the low dose of nicotine. The withdrawal of the high dose of chronic nicotine gradually returned the decreased plasma vasopressin concentration, and its content in and release from the neural lobe to control values within 2 weeks. However, vasopressin content in the hypothalamus started to decline 1 week after nicotine withdrawal and persisted to decline for at least 3 subsequent weeks. The withdrawal of the high dose was associated with a marked suppression of high K⁺-stimulated vasopressin release from the neural lobe for a period of 4 weeks. The withdrawal of the low dose of nicotine exhibited a significant decline in plasma vasopressin concentration for up to 2 weeks only following chronic nicotine withdrawal, tending to return subsequently to control levels.     

Local transport kinetics of glucose during acute and chronic nicotine infusion in rat brains

Summary. Acute and chronic infusion of nicotine is known to result in a distinct increase in local cerebral glucose utilization (LCGU) in several brain structures. The present study addresses the question whether this increase in LCGU is paralleled by a local change in glucose transport in rat brain. Nicotine was infused either acutely for 3 hours or chronically by osmotic minipumps for one week. Local rate constants for glucose transport were measured in brain cryosections using the 3-O-[¹⁴C]methylglucose method. Local rate constants K₁ and k₂ were lower in part of the brain structures during acute (−10% to −20%) and in nearly all structures during chronic (−39% to −41%) nicotine. The finding of a decreased glucose transport during chronic nicotine was confirmed by additional experiments of 3-O-[¹⁴C]methylglucose transfer in an epithelial cell culture. It is concluded that acute and chronic nicotine infusion results in decreased glucose transport although LCGU is either unchanged or increased. Received December 12, 1997; accepted February 2, 1998     

Electrophysiological study of conditioning lesion effect on rat sciatic nerve regeneration following either prior section or freeze. I. Intensity and time course

A peripheral nerve lesion performed distally prior to a proximal axotomy is known to result in an increase in the rate of regeneration of both sensory and motor fibres. This phenomenon is called the 'conditioning lesion effect'. The aim of this study was to determine whether or not the kind of the conditioning lesion influences the intensity and the time course of the conditioning lesion effect. The prior lesion was performed on the tibial nerve of rats at the ankle either by cutting the nerve or freezing it by means of a 1 mm diameter liquid nitrogen cryod. At several points in time up to 28 days a second (or test) lesion consisting of a freeze was performed on the sciatic nerve at the middle part of the thigh. The regeneration of the fastest growing fibres of the sciatic nerve was measured electrophysiologically 5, 7 and 9 days after the test lesion. The nerve was surgically removed, immediately mounted in a recording nerve chamber and stimulated proximally to the test lesion. The distance between the test lesion and the most distal point where an evoked nerve potential was detectable was taken as the regenerated nerve length. Then the rate of regeneration was calculated and the initial delay was estimated by means of a linear regression plotting the regenerated nerve lengths against the days of recording. All the results were compared to those of a control group where the test lesion alone was performed. The increase in the maximal rate of regeneration was greater following a prior section (+25%) than following a prior freeze (+12%). Following a prior section, the rate of regeneration began to be significantly increased for a conditioning interval of 4 days, and went on until a conditioning interval of 28 days. By contrast, after a prior freeze the rate of regeneration was significantly increased solely for an interval of 14 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of an autologous transplant on patterns of regeneration in rat sciatic nerve

Autologous transplants are often used in repair of peripheral nerve injury. Quantitative evaluation of the results of such a transplant is obviously desirable. In previous study, we determined numerical and cytologic parameters of the regeneration that followed transection of rat sciatic nerve, but no transplant was used. This work now serves as a basis for evaluating the use of an autologous transplant in the same transection paradigm. Our procedure is to remove 8 mm of sciatic nerve in the thigh. The removed segment is then put into the center of a silicone tube and the proximal and distal stumps of the severed nerve are placed into the ends of the tube. The data show: (1) a high percentage of successful regenerations; (2) a relatively large nerve in the gap; (3) a typical outer perineurium underlying the epineurium; (4) a well-developed fascicular perineurium; and (5) approximately equal numbers of myelinated and unmyelinated axons in the gap and distal stump. If a transplant is not used there are: (1) a greater number of failures of regeneration; (2) a smaller nerve in the gap; (3) a less well-developed fascicular perineurium; (4) unequal numbers of axons in the gap as compared to the distal stump; and (5) no outer perineurium forms. The presence of a typical outer perineurium after a transplant and its absence if a transplant is not used is probably the most striking cytologic difference between the two paradigms. The equal numbers of axons in the gap and distal stump following regeneration after transplantation presumably indicate that all axons in the gap enter the distal stump without branching or ending blindly, a situation that is presumably beneficial and contrasts with the findings when a transplant is not used. Both paradigms show a remarkable increase in the density of blood vessels in the regenerated nerve in the gap between the two stumps. These findings will serve as a basis for further studies on the mechanisms of peripheral nerve regeneration.     

Proteolytic processing, axonal transport and differential distribution of chromogranins A and B, and secretogranin II (secretoneurin) in rat sciatic nerve and spinal cord

The chromogranin family comprises chromogranin A and B, and secretogranin II. The present study has focused on the axonal transport of chromogranins/secretogranin II and their detailed distribution in peripheral nerves and the spinal cord. With radioimmunoassay (RIA) and column chromatography, we first studied the processing of chromogranin B and secretogranin II during axonal transport. No larger precursors of these peptides were detected in the sciatic nerves, indicating that they are already processed to a high degree early during axonal transport. We also analysed nerve segments above and below a crush, using RIA, in order to compare these accumulation data with those obtained by the cytofluorimetric-scanning (CFS) technique. For the latter technique, the amounts of accumulation distal to the crush (presumably representing recycling and retrogradely transported peptides) were 30-40% of the amounts in the proximal accumulation for chromogranin A and secretoneurin, in contrast to chromogranin B, which showed 15% recycling. With the RIA, the corresponding values for secretoneurin and PE-11 (antibody against chromogranin B) were 42% and 14%, respectively. Therefore, the data obtained by CFS were in excellent agreement with those obtained by RIA. In crushed sciatic nerves, chromogranin A was present in large axons as well as in small- and medium-sized axons. Chromogranin B was mainly restricted to large axons, while secretoneurin was localized to bundles of small axons. This differential distribution was also found in the spinal roots and in the peripheral terminals. Chromogranin A was present in both ventral and dorsal roots, and chromogranin B was detected in ventral roots and in large sensory axons in the dorsal roots. Secretoneurin was dominant in the dorsal root. Double-labelling studies with antibodies against choline acetyltransferase/vesicular acetylcholine transporter, or against tyrosine hydroxylase, confirmed that chromogranin A was distributed in cholinergic, sensory, as well as adrenergic neurons. Chromogranin B was mainly present in cholinergic motor neurons and large sensory neurons, and secretoneurin was restricted to adrenergic and sensory neurons. The present study demonstrates that chromogranins A and B, and secretoneurin are transported with fast axonal transport in the peripheral nerves, with different amounts of recycling, and that they are differentially distributed in different types of neurons in the peripheral nervous system and the spinal cord, suggesting that each of them may play a special role in subsets of neurons.     

维拉帕米与神经生长因子促进大鼠坐骨神经再生的协同作用

背景：实验证明周围神经损伤时,轴突的变性与神经元凋亡都与Ca2+的超载有着极其密切的关系。 目的：利用大鼠坐骨神经损伤模型观察L型钙离子通道阻滞剂维拉帕米联合神经生长因子促进周围神经再生的协同作用。 设计、时间及地点：随机对照动物实验,于2007-04/2008-11在辽宁医学院手外科实验室完成。 材料：同系健康雄性SD大鼠32只,体质量220~260 g;维拉帕米为辽宁卫星制药厂产品,国药准字H21022847;神经生长因子为sigma公司产品。 方法：同系SD大鼠32只随机分为4组,每组8只,分别在右侧梨状肌下缘5 mm切断坐骨神经后立即原位缝合造成坐骨神经损伤模型。①维拉帕米+神经生长因子组：腹腔注射维拉帕米4 mg/(kg•d),术侧腓肠肌肉注射神经生长因子0.6 μg/d。②维拉帕米组：腹腔注射维拉帕米4 mg/(kg•d),术侧腓肠肌注射等量生理盐水。③神经生长因子组：术侧腓肠肌注神经生长因子0.6 μg/d,并腹腔注射等量生理盐水。④空白对照组：分别腹腔,肌注等量生理盐水。以左侧坐骨神经为正常对照。 主要观察指标：术后12周对各组再生神经进行大体观察,神经电生理测定,组织学观察及有髓神经纤维计数。 结果：术后12周,维拉帕米+神经生长因子组足部溃疡的出现与愈合以及展抓反射出现的时间均早于其他各组。神经传导速度恢复率和有髓神经纤维计数恢复率分析表明：维拉帕米+神经生长因子组>维拉帕米组>神经生长因子组>空白对照组。光镜和电镜下可见：维拉帕米+神经生长因子组再生的神经纤维最多,轴突较为粗大。有髓神经纤维多,髓鞘完整,优于其他3组。神经纤维直径恢复率分析表明：维拉帕米+神经生长因子组>神经生长因子组>维拉帕米组>空白对照组。 结论：维拉帕米与神经生长因子对促进周围神经形态结构和功能的恢复均具有明显的协同作用。     

Axonal transport of substance P in the vagus and sciatic nerves of the guinea pig

The axonal transport and apparent subcellular distribution of substance P-like immunoreactive material (SPLI) were examined in nerves of guinea pigs by means of a sensitive radioimmunoassay and by immunohistofluorescence. Crushes or ligations were made at various levels above and below the nodose ganglion of the vagus, on the sciatic nerve, and on the central process of the S1 spinal ganglion. From the relative rates of accumulation of SPLI in the adjacent segments, it was concluded that the bulk of the substance P produced in the sensory ganglion cells was being exported toward the terminal regions of their peripheral branches. The average velocity of transport of SPLI in the peripheral direction was calculated to be 1 mm/h in the sciatic nerve and 1.25 mm/h in the vagus. The removal of SPLI from regions of nerve distal to a ligature indicated that only 26% of the peptide in vagus nerve and 17% of the peptide in sciatic nerve was available for rapid transport. It was therefore estimated that the mean velocity of the moving fraction was 5-6 mm/h. Stop-flow experiments with local cooling and rewarming in vivo suggested that some SPLI may have been transported as rapidly as 10 mm/h. The behavior of SPLI during ultracentrifugation of nerve and ganglion extracts indicated that this peptide was normally present both in a soluble form and in association with particles but was transported primarily in the latter form.