Orphanin FQ antagonizes the analgesic effect of 5-HT in rat brain

Orphanin FQ (OFQ) is a new modulatory peptide which was found in 1994. It mediates in morphine analgesia and electroacupuncture analgesia. The interaction between OFQ and 5-hydroxytryptamine (5-HT) on analgesia was observed using the method of intracere-broventricular microinjection. The results showed that cumulative i. c. v. administration of gradually increasing doses of 5-HT produced a dose-dependent analgesia, and administration of different doses of OFQ separateness had no significant effect on tail flick latency, but 1 or 10 μg OFQ could reverse the analgesia induced by 5-HT, suggesting that OFQ could antagonize the analgesia induced by 5-HT in rat brain.     

八肽胆囊收缩素抗血清翻转针刺耐受的电生理学研究

动物整体水平研究证实，八肽胆囊收缩素抗血清（ＣＣＫ－ＡＳ）可翻转电针耐受，而ＣＣＫ－ＡＳ本身不影响基础痛阈。本文采用记录神经元放电的方法证明：脑室注射ＣＣＫ－ＡＳ能翻转对长时间电针产生耐受效应的大鼠丘脑束旁核痛兴奋神经元（ＰＥＮ）和痛抑制神经元（ＰＩＮ）的电活动，使电针镇痛效应重新出现。而脑室注射正常兔血清（ＮＲＳ）对产生电针耐受效应的ＰＥＮ和ＰＩＮ的电活动无影响。从细胞水平得到的这一结果与整体水平研究的证据相一致。提示，内源性ＣＣＫ－８参与电针耐受可能是电针镇痛受到拮抗的机制之一。这一发现同时为临床医学实践提供了进一步的依据。     

硬膜外注射吗啡用于下腹部手术后镇痛

目的 观察下腹部术后硬膜外注射吗啡镇痛的疗效。方法 择期下腹部手术病人５１例,待手术缝皮时,经硬膜外导管注射吗啡液（吗啡２ｍｇ加生理盐水１０ｍＬ）用于术后镇痛。结果 注药前后ＨＲ,ＭＡＰ,ＳＰＯ２无显著性并异（Ｐ〉０．０５）;术后２４ｈＶＡＳ显著高于术后４ｈ（Ｐ〈０．０５）,但无临床意义;术后并发恶心呕吐６例,尿潴留２例,瘙痒１例。结论 硬膜外注射吗啡用于腹部手术后镇育取得了良好的疗效,值得推广。     

BDNF from microglia causes the shift in neuronal anion gradient underlying neuropathic pain

Neuropathic pain that occurs after peripheral nerve injury depends on the hyperexcitability of neurons in the dorsal horn of the spinal cord. Spinal microglia stimulated by ATP contribute to tactile allodynia, a highly debilitating symptom of pain induced by nerve injury. Signalling between microglia and neurons is therefore an essential link in neuropathic pain transmission, but how this signalling occurs is unknown. Here we show that ATP-stimulated microglia cause a depolarizing shift in the anion reversal potential (E(anion)) in spinal lamina I neurons. This shift inverts the polarity of currents activated by GABA (gamma-amino butyric acid), as has been shown to occur after peripheral nerve injury. Applying brain-derived neurotrophic factor (BDNF) mimics the alteration in E(anion). Blocking signalling between BDNF and the receptor TrkB reverses the allodynia and the E(anion) shift that follows both nerve injury and administration of ATP-stimulated microglia. ATP stimulation evokes the release of BDNF from microglia. Preventing BDNF release from microglia by pretreating them with interfering RNA directed against BDNF before ATP stimulation also inhibits the effects of these cells on the withdrawal threshold and E(anion). Our results show that ATP-stimulated microglia signal to lamina I neurons, causing a collapse of their transmembrane anion gradient, and that BDNF is a crucial signalling molecule between microglia and neurons. Blocking this microglia-neuron signalling pathway may represent a therapeutic strategy for treating neuropathic pain.     

大鼠SNL神经性疼痛模型的建立

摘要:目的　建立大鼠L5和L6脊神经结扎(Spinal nerve ligation,SNL)疼痛模型并进行评价, 方法　根据大鼠痛阈值测定结果,选择90只符合要求的SD雄性大鼠进行手术操作,术后每隔1d测定大鼠后足的机械痛阈值,比较术前和术后大鼠对疼痛刺激的反应变化。 结果　术后大鼠左足的痛阈值逐渐降低,至10d 后趋于稳定,与术前有明显差异(P≤0.01);右足的痛阈值微有升高,保持在稳定的水平内。 结论　本研究建立的大鼠SNL模型机械痛阈变化明显,稳定性好,可靠性高,可以作为大鼠一种神经病理性疼痛的模型。     

Vasopressin alters female sexual behaviour by acting on the brain independently of alterations in blood pressure

Subcutaneous (s.c.) administration of Arg-vasopressin (AVP) prolongs retention of a learned behaviour and elevates arterial blood pressure. Intracerebroventricular (i.c.v.) injection of a thousandfold lower dose of AVP than needed with s.c. injection produces the same behavioural effect, suggesting that AVP acts on the brain to control behaviour. However, as i.c.v. injection of AVP also elevates arterial blood pressure, it was suggested that AVP, and perhaps other peptides as well, influences behaviour indirectly by eliciting a peripheral response, for example blood pressure changes, rather than by acting directly on the brain. The suprachiasmatic nuclei (SCN) of the hypothalamus, a source of vasopressin production, inhibit sexual receptivity in oestradiol-17 beta-treated ovariectomized rats during the light phase of the daily lighting cycle, leading to speculation that vasopressin might inhibit sexual behaviour. Here we report that i.c.v. injections of AVP (1, 4 or 10 ng) inhibit sexual behaviour in receptive rats. This behavioural response is prevented by i.c.v. injection of an antiserum to AVP 30 min before AVP injection. Subcutaneous injection of a high dose of AVP (1 microgram) has no behavioural effect but elevates arterial blood pressure within 30 min of administration. Intracerebroventricular injection of a behaviourally effective dose of AVP (1 ng) has no effect on blood pressure. The results provide direct evidence that AVP can alter behaviour by an action on the brain and independently of its effect on blood pressure.     

Reversal of pathological pain through specific spinal GABAA receptor subtypes

Inflammatory diseases and neuropathic insults are frequently accompanied by severe and debilitating pain, which can become chronic and often unresponsive to conventional analgesic treatment. A loss of synaptic inhibition in the spinal dorsal horn is considered to contribute significantly to this pain pathology. Facilitation of spinal gamma-aminobutyric acid (GABA)ergic neurotransmission through modulation of GABA(A) receptors should be able to compensate for this loss. With the use of GABA(A)-receptor point-mutated knock-in mice in which specific GABA(A) receptor subtypes have been selectively rendered insensitive to benzodiazepine-site ligands, we show here that pronounced analgesia can be achieved by specifically targeting spinal GABA(A) receptors containing the alpha2 and/or alpha3 subunits. We show that their selective activation by the non-sedative ('alpha1-sparing') benzodiazepine-site ligand L-838,417 (ref. 13) is highly effective against inflammatory and neuropathic pain yet devoid of unwanted sedation, motor impairment and tolerance development. L-838,417 not only diminished the nociceptive input to the brain but also reduced the activity of brain areas related to the associative-emotional components of pain, as shown by functional magnetic resonance imaging in rats. These results provide a rational basis for the development of subtype-selective GABAergic drugs for the treatment of chronic pain, which is often refractory to classical analgesics.     

Inhibiting pain with pain— A basic neuromechanism of acupuncture analgesia

(i) The structure and function of the meridian (channel and collateral) described by ancient medical doctors may correspond to the blood circulation, nerve control and neurohumoral modulation of modern medicine. (ii) The needling, which can injure the tissue, is a noxious stimulation inducing pain. Acupuncture manipulation, such as lifting and thrusting, twisting and twirling, or electroacupuncture (EA) with the sufferable biggest intensity for patients should be a stronger pain stimulation. The needling sensation of soreness, numbness, distension and heaviness is a deep pain. (iii) There is an intrinsic analgesic system in brain, which centers around the periventricular and periaqueductal grey matter, contains endorphins as possible mediators, goes through the descending inhibition system in medulla oblon-gata, and acts on the gating mechanism in spinal cord. Itcould be producing analgesia while the system is activated. (iv) NRM might be a supraspinal center modulating pain, and the R-S neurons could form a basic circuit of negative feedback modulating pain. The discovery of excitatory-inhibitory reversible R-S neurons may give a neuro-physiological explanation for the double direction modulation of acupuncture at acupoint. (v) Non-noxious stimulation such as massage or stroking could excite type I and n afferent fibers, producing a weaker and transient analgesia through the spinal mechanism. When the acupoint is near the pain area, the afferent information from them could be converged on the same and neighboring spinal segments, the light acupuncture or low intensity of EA also has analgesic effects, showing acupoint specificity. But the acupoint specificity is not limited in a specially designated channel line, and it is closely related to the segment of innervation. (vi) While acupuncture manipulation of lifting and thrusting, twisting and twirling or a high intensity of EA is used, because the intensities of these stimulations exceed the threshold of afferent C fibers, they could fully excite Ⅲ(Aδ) and Ⅳ (C) afferent fibers, producing a strong and lasting analgesia, mainly through the supraspinal negative feedback mechanism modulating pain, it has curative effects. Therefore, the essence of acupuncture analgesia may chiefly be inhibiting pain with pain.     

Analgesia and hyperalgesia from GABA-mediated modulation of the cerebral cortex

It is known that pain perception can be altered by mood, attention and cognition, or by direct stimulation of the cerebral cortex, but we know little of the neural mechanisms underlying the cortical modulation of pain. One of the few cortical areas consistently activated by painful stimuli is the rostral agranular insular cortex (RAIC) where, as in other parts of the cortex, the neurotransmitter gamma-aminobutyric acid (GABA) robustly inhibits neuronal activity. Here we show that changes in GABA neurotransmission in the RAIC can raise or lower the pain threshold--producing analgesia or hyperalgesia, respectively--in freely moving rats. Locally increasing GABA, by using an enzyme inhibitor or gene transfer mediated by a viral vector, produces lasting analgesia by enhancing the descending inhibition of spinal nociceptive neurons. Selectively activating GABA(B)-receptor-bearing RAIC neurons produces hyperalgesia through projections to the amygdala, an area involved in pain and fear. Whereas most studies focus on the role of the cerebral cortex as the end point of nociceptive processing, we suggest that cerebral cortex activity can change the set-point of pain threshold in a top-down manner.     

P2X4 receptors induced in spinal microglia gate tactile allodynia after nerve injury

Pain after nerve damage is an expression of pathological operation of the nervous system, one hallmark of which is tactile allodynia-pain hypersensitivity evoked by innocuous stimuli. Effective therapy for this pain is lacking, and the underlying mechanisms are poorly understood. Here we report that pharmacological blockade of spinal P2X4 receptors (P2X4Rs), a subtype of ionotropic ATP receptor, reversed tactile allodynia caused by peripheral nerve injury without affecting acute pain behaviours in naive animals. After nerve injury, P2X4R expression increased strikingly in the ipsilateral spinal cord, and P2X4Rs were induced in hyperactive microglia but not in neurons or astrocytes. Intraspinal administration of P2X4R antisense oligodeoxynucleotide decreased the induction of P2X4Rs and suppressed tactile allodynia after nerve injury. Conversely, intraspinal administration of microglia in which P2X4Rs had been induced and stimulated, produced tactile allodynia in naive rats. Taken together, our results demonstrate that activation of P2X4Rs in hyperactive microglia is necessary for tactile allodynia after nerve injury and is sufficient to produce tactile allodynia in normal animals. Thus, blocking P2X4Rs in microglia might be a new therapeutic strategy for pain induced by nerve injury.     

The effects of the synthetic nocistatin on blood vessel activities

Nocistatin was synthesized by the solid-phase peptide synthesis method. Its effects on rat systemic arterial pressure; rat hindquarter vascular bed resistance; tension of rabbit pectoral, abdominal, femoral aorta muscle strips without endothelium; and nociceptin induced decreases of rat systemic arterial pressure were determined. The results showed that nocistatin can increase the systemic arterial pressure, increase the hindquarter vascular bed resistance and induce the contraction significantly of abdominal, femoral aorta muscle strips without endotheiium; it has no significant effect on tension of pectoral aorta muscle strips, it cannot antagonize significantly the decrease of rat systemic arterial pressure induced by nociceptin. These results suggest that nocistatin has some important effects on blood vessel activities.     

Mechanism for chronic pain generation

Neuropathic pain and the other abnormalities of sensation induced by axon injury or by peripheral nerve inflammation should result from functional compensations of the injured neurons during their regeneration. Ectopic distribution of proteins related to Na⁺, K⁺ and Ca²⁺ channels as well as of receptors on both membranes of injured axon and its cell body becomes a main pacemaker from which spontaneous ectopic afferent of primary sensatory neurons and crosstalk between neurons occur. Abnormal ectopic afferent activities lead to disorders of the sensation, such as hyperalgesia, allodynia, spontaneous pain and paraesthesia. Administration of some ion channel agents and/or α2-adrenergic blockers has shown efficiency in preventing neuropathic pain development and in relieving neuropathic pain.     

吗啡人工抗原的合成及多克隆抗体的制备

利用化学法合成吗啡人工抗原,将此抗原免疫新西兰大白兔制备抗吗啡多克隆抗体.利用混合酸酐法将吗啡人工抗原分别与蛋白质载体BSA及OVA偶联,经蛋白质电泳以及紫外扫描检测,证明吗啡人工抗原合成成功.用间酶联免疫检测法检测,证明制备得到了高效价的吗啡多克隆抗体血清,且与吗啡人工抗原具有高特异性反应,可用于吗啡免疫学检测方法的研究.     

牛肾上腺髓质8-22肽增强吗啡的抗伤害作用

采用甩尾反射实验研究椎管内注射感觉神经元特异性受体的激动剂牛肾上腺髓质8-22肽(bovine adrenal medulla 8-22,BAM8-22)对吗啡抗伤害作用的影响.结果表明,BAM8-22本身并不能改变伤害性热刺激引起的甩尾反射潜伏期,但与吗啡混合使用时,能明显增强吗啡的抗伤害作用.0.1,1,10 nmol BAM8-22与0.3 μg 吗啡混合进行椎管内注射,能剂量依赖地增强吗啡的抗伤害作用.0.1 nmol BAM8-22分别与0.2,1,5 μg吗啡混合进行椎管内注射后,吗啡的抗伤害作用分别为35.1%,61.8%,72.7%,明显高于吗啡对照组的13.0%,30.7%,52.8%(P＜0.01).本研究表明,BAM8-22能增强吗啡的抗伤害作用,暗示感觉神经元特异性受体(SNSR)参与调制阿片受体的抗伤害过程.     

卡马西平对吗啡依赖小鼠戒断症状的影响

目的 :观察卡马西平对纳洛酮诱发的吗啡依赖小鼠戒断症状的作用。方法 :皮下注射吗啡 7天 ,建立小鼠吗啡依赖模型。纳洛酮催瘾前 30分钟 ,分组灌胃不同药物 ,观察小鼠戒断反应。结果 :卡马西平(15 0 mg· kg- 1 )及可乐定 (0 .2 4 m g· kg- 1 )能明显降低小鼠跳跃次数 ,减轻体重下降趋势 ,与阴性对照组比较差异有显著意义 ;对腹泻症状也有缓解作用。结论 :单用卡马西平能有效控制纳洛酮诱发的小鼠戒断症状 ,效果与可乐定相似     

丁丙诺啡静脉自控镇痛在脊柱外科术后的应用

目的观察丁丙诺啡静脉病人自控镇痛(PICA)在脊柱内固定术后镇痛的疗效.方法 60例因脊柱疾患而需行内固定的患者随机分为吗啡组(M组)、曲马多组(T组)、丁丙诺啡组(B组),每组20例.B组泵盒中加入丁丙诺啡1.5 mg,欧必停2.5 mg.各组都用生理盐水稀释至100 mL.镇痛方法采用负荷剂量 持续输注 病人自控模式,设置负荷量5 mL;持续剂量为2 mL/h;锁定时间为15 min;PCA剂量为0.5 mL.观察镇痛效果和不良反应.结果 3组患者术后镇痛效果评估M组、T组与B组相比无显著差异;M组的不良反应发生率为50%,T组的不良反应发生率为40%,B组的不良反应发生率为20%,3组比较B组与另外两组有显著性差异(P<0.05),3组患者只有T组有1例患者发生呼吸抑制.结论丁丙诺啡PICA用于脊柱内固定术后的镇痛,疗效满意,不良反应较少.     

Effect of tramadol on immune responses and nociceptive thresholds in a rat model of incisional pain

Objective： To evaluate the effects oftramadol on the proinflammatory responses in a rat model of incisional pain by investigating its effects on nociceptive thresholds and serum interleukin-6 （IL-6） and IL-2 levels. Methods： Forty-two male Sprague-Dawley （SD） rats scheduled for plantar incision were randomly divided into 7 groups 01=6 in each group）. Rats in Group 1 receiving general anesthesia with no incision were served as control; At 30 min before skin incision, Groups 2-5 were given 5 ml normal saline or 1, 10, and 20 mg/kg tramadol, respectively, intraperitoneally （i.p.）; Group 6 received 10 mg/kg tramadol after operation; Group 7 received 10 mg/kg tramadol before incision, followed by 200 μg/kg naloxone after operation. Mechanical allodynia was measured by electronic yon Frey filament to evaluate the nociceptive thresholds 1 h before incision, and 1 h and 2 h after operation. Serum IL-6 and IL-2 levels were measured by enzyme-linked immunosorbent assay （ELISA） 2 h after operation. Results： Mechanical thresholds decreased significantly and serum IL-6 level increased significantly after operation in Group 2 compared with control （P〈0.01）, and these changes were reversed respectively by tramadol in a dose-dependent manner （P〈0.05 and P〈0.01, respectively）. IL-2 level remained unchanged after operation in Group 2, but decreased in Group 3 （P〈0.05）, then gradually returned to the normal level in Groups 4 and 5. The intraperitoneally injected tramadol （10 and 20 mg/kg） produced a potent and dose-dependent antinocicptive effect on the lesioned paw. The antinocicptive effects of tramadol were partially an- tagonized by naloxone （200 μg/kg）, suggesting an additional non-opioid mechanism. Conclusion： The results suggest that tramadol could be a good choice for the treatment of pain under the conditions that immunosuppression may be particularly contraindicated.     

Stimulation of food intake in rats by centrally administered hypothalamic growth hormone-releasing factor

Hypothalamic growth hormone-releasing factors (GRFs) have been purified recently from human pancreatic (hp) tumours and from rat hypothalamus (rh). GRF peptides have strong homology with peptides of the glucagon, vasoactive intestinal polypeptide and PHI-27 family. Aside from their potent actions on release of somatotropin, no other biological actions of GRFs have been reported. GRF has been localized in neurones bordering the ventromedial hypothalamic nucleus, a region associated frequently with experimental analysis of feeding behaviour. We now report that intracerebroventricularly (i.c.v.)-administered rhGRF and hpGRF(1-40) in doses of 0.2, 2.0 and 20.0 pmol, produced an increase in food intake in hungry rats. This effect seemed to be specific to GRF as i.c.v. injections of a structurally related but physiologically inactive peptide in the same doses had no effect on feeding. In addition, peripheral injections of rhGRF or growth hormone had no effect on food intake, suggesting that the present effects may be mediated centrally. Injections (i.c.v.) of rhGRF (0.2, 2.0 and 20.0 pmol) had no effect on general activity, suggesting that GRF does not produce nonspecific arousal.     

A gastrin-releasing peptide receptor mediates the itch sensation in the spinal cord

Itching, or pruritus, is defined as an unpleasant cutaneous sensation that serves as a physiological self-protective mechanism to prevent the body from being hurt by harmful external agents. Chronic itch represents a significant clinical problem resulting from renal diseases and liver diseases, as well as several serious skin diseases such as atopic dermatitis. The identity of the itch-specific mediator in the central nervous system, however, remains elusive. Here we describe that the gastrin-releasing peptide receptor (GRPR) plays an important part in mediating itch sensation in the dorsal spinal cord. We found that gastrin-releasing peptide is specifically expressed in a small subset of peptidergic dorsal root ganglion neurons, whereas expression of its receptor GRPR is restricted to lamina I of the dorsal spinal cord. GRPR mutant mice showed comparable thermal, mechanical, inflammatory and neuropathic pain responses relative to wild-type mice. In contrast, induction of scratching behaviour was significantly reduced in GRPR mutant mice in response to pruritogenic stimuli, whereas normal responses were evoked by painful stimuli. Moreover, direct spinal cerebrospinal fluid injection of a GRPR antagonist significantly inhibited scratching behaviour in three independent itch models. These data demonstrate that GRPR is required for mediating the itch sensation rather than pain, at the spinal level. Our results thus indicate that GRPR may represent the first molecule that is dedicated to mediating the itch sensation in the dorsal horn of the spinal cord, and thus may provide a central therapeutic target for antipruritic drug development.     

Modulation of glycine receptor chloride channels by cAMP-dependent protein kinase in spinal trigeminal neurons

Glycine is an important inhibitory transmitter in the brainstem and spinal cord. In the trigeminal subnucleus caudalis (medullary dorsal horn) and in the spinal dorsal horn (the relaying centres for processing pain and sensory information), glycine inhibits the glutamate-evoked depolarization and depresses firing of neurons. The binding of glycine to its receptor produces a large increase in Cl- conductance, which causes membrane hyperpolarization. The selectivity and gating properties of glycine receptor channels have been well characterized; the glycine receptor molecules have also been purified. The amino-acid sequence, deduced from complementary DNA clones encoding one of the peptides (the 48K subunit), shows significant homology with gamma-aminobutyric acid A (GABAA) and nicotinic acetylcholine receptor subunits, suggesting that glycine receptors may belong to a superfamily of chemically gated channel proteins. However, very little is known about the modulation of glycine receptor channels. We have investigated the regulation of strychnine-sensitive glycine receptor channels by cyclic AMP-dependent protein kinase in neurons isolated from spinal trigeminal nucleus of rat and report here that the protein kinase A dramatically increased the glycine-induced Cl- currents by increasing the probability of the channel openings. GS protein, which is sensitive to cholera toxin, was involved in the modulation.