NMDA受体拮抗剂APV抑制福尔马林诱导的大鼠伤害性行为反应

目的：检测NMDA受体拮抗剂DL-2-amino-5-phosphonovaleric acid(APV)对福尔马林诱导的大鼠伤害性行为反应的镇痛效应。方法：在大鼠左足趾部sc福尔马林诱导化学损伤性行为反应，经蛛网膜下腔引入药物，观察对此行为反应的抑制效应。结果：APV剂量依赖地抑制福尔马林诱导的持续性伤害性行为反应并有时间作用特点；APV对其中的反射性缩腿反应也有抑制作用，但没有时间作用特点。结论：NMDA受体在脊髓痛觉传递和疼痛反应过程中起重要作用；但NMDA受体拮抗剂APV是否有直接的镇痛效应仍需进一步分析。     

CNQX对伤害性刺激隐神经诱发大鼠脊髓Fos蛋白表达的影响

目的 探讨伤害性刺激隐神经（SN）能否诱发脊髓神经元Fos蛋白表达及发生机制.方法 应用免疫组化方法观察伤害性刺激SN和尾静脉注射谷氨酸非NMDA受体拮抗剂（CNQX）后诱发脊髓神经元Fos蛋白表达的变化.结果 伤害性刺激SN后,诱导脊髓神经元Fos蛋白表达显著增强,CNQX拮抗了Fos蛋白表达的显著增强.结论 以伤害性刺激SN模拟躯体痛后,CNQX拮抗了伤害性刺激SN引起的脊髓神经元Fos蛋白表达的显著增加,表明非NMDA受体在躯体痛的调控中起到了重要的作用.     

雌激素对慢性内脏痛雌鼠的敏化作用及其机制

目的探讨雌激素对慢性内脏痛雌鼠痛反应的影响及其与脊髓NMDA受体的关系。方法在♀大鼠新生期给予数次结直肠扩张刺激,成年后分为高、低雌激素组,用腹外斜肌放电水平来评价成鼠内脏痛觉敏感性,用NMDA受体拮抗剂D(-)-2-amino-5-phosphonopentanoic acid(AP-5)鞘内给药比较两组大鼠脊髓NMDA受体的功能。结果 (1)模型鼠高雌激素组的内脏痛反应比低雌激素组的反应强。(2)AP-5鞘内给药对内脏痛反应的抑制作用在模型鼠两组中的差异无统计学意义。结论高雌激素可加重模型雌鼠的内脏痛反应,雌激素不能使模型雌鼠脊髓背角的NMDA受体功能上调。     

鞘内注射纳洛酮对小剂量丙泊酚抗内脏伤害作用的影响

目的研究丙泊酚内脏痛镇痛机制是否与脊髓阿片受体有关。方法56只成年雄性SD大鼠蛛网膜下腔埋入导管后随机均分为8组，分别鞘内预注生理盐水（NS）或纳洛酮2μg／只、4μg／只或8μg／只，再腹腔注射NS或丙泊酚10mg／kg，随后采用结直肠扩张的内脏痛实验动物模型，以腹壁明显收缩变平的最小扩张压力值作为内脏痛反应（VMR）阈值，观察大鼠60min内内脏痛阈的变化。结果单纯腹腔注射小剂量丙泊酚后，5～25min内大鼠内脏痛阈显著升高（P〈0．01），10min达高峰（％MPE=37．2％）；单纯鞘内预注不同剂量纳洛酮大鼠内脏痛阈无明显变化（P〉0．05）；先鞘内预注不同剂量纳洛酮再腹腔注射丙泊酚后，丙泊酚所致抗内脏伤害作用被不同程度的减弱。结论（1）小剂量丙泊酚对内脏伤害刺激具有抑制作用；（2）纳洛酮剂量依赖、时间依赖地拮抗丙泊酚的抗内脏伤害作用，其作用机制与脊髓阿片受体有关。     

溴氰菊酯对大鼠神经细胞内游离钙的影响

目的 研究溴氰菊酯对大鼠神经细胞内游离钙([Ca^2 ]i)的影响,并探讨其可能机制。方法 用溴氰菊酯处理分离的大鼠脑细胞,用Fura-2/AM为细胞内钙离子荧光指示剂,测定神经细胞内游离钙浓度;并利用NMDA受体竞争性拮抗剂AP5、非竞争性拮抗剂MK－801、Na^ 离子通道阻断剂TTX、电压依赖性钙通道阻断剂尼莫地平,探讨了溴氰菊酯影响胞内钙的可能机制;另外还观察了去除胞外钙时溴氰菊酯对胞内钙的影响情况。结果 溴氰菊酯浓度在0－200nmol/L范围内,可以显著提高大鼠皮层和海马细胞内游离钙的浓度（P＜0．01）,并有良好的剂量－反应关系（相关系数分别为r=0.964,r=0.981);AP5、MK－801和TTX可以有效阻断溴氰菊酯的升钙作用;而尼莫地平则无影响;去除胞外钙时,溴氰菊酯的升钙作用也消失。结论 溴氰菊酯导致的胞内钙升高,主要是由谷氨酸激活NMDA受体门控钙通道引起的胞外钙内流,和电压依赖性钙通道及胞内钙库释放无关。     

丙泊酚镇痛作用及其与阿片受体的关系

目的观察丙泊酚在亚睡眠剂量时对大鼠的抗伤害作用及其与阿片受体的关系。方法选用成年雄性Wistar大鼠,通过甩尾（TFL）、电刺激鼠尾嘶叫（TSV）和结直肠扩张（CIm）法测定动物的痛阈。观察丙泊酚20mg／kg和同时应用阿片受体拮抗剂纳洛酮1mg／kg对大鼠痛阈的影响,以等效剂量硫喷妥钠作为对照。结果丙泊酚20mg／kg显著提高TSV、CRD和TFL伤害性反应阈值。采用TSV抗伤害作用时间持续60min以上,而采用TFL和CRD抗伤害作用≤30min。等效剂量硫喷妥钠无论采用TFL、TSV或CRD都无明显提高大鼠痛阈的作用。纳洛酮1mg／kg可以拮抗或部分拮抗丙泊酚引起的抗伤害作用。结论与等效量硫喷妥钠相比,亚睡眠剂量的丙泊酚在大鼠能产生一定的镇痛效应;这种镇痛效应可能与丙泊酚间接作用于中枢阿片受体有关。     

P物质增强大鼠鞘内注射D—丝氨酸诱发的热痛过敏

目的：研究脊髓伤害性信息传递中P物质（SP）与N－甲基－D－天冬氨酸（NMDA）受体甘氨酸位点激动剂D－丝氨酸（D-serine)之间的功能联系。方法：在浅麻大鼠,采用行为学方法,测定甩尾反射潜伏期（TFL）并结合鞘内给药途径观察药物作用。结果：鞘内注射D-serine 1000nmol后1．5分钟,TEL明显缩短;在注射D-serine 10nmol前6分钟鞘内施加SP 0.05nmol,明显增强D-serine 10nmol引起的TEL缩短效应;选择性NMDA受体甘氨酸位点拮抗剂7－氯犬尿酸1pmol及非选择性PKC抑制剂H－7 10μmol均可阻断这种增强作用。结论：SP可使D－丝氨酸诱发的热痛过敏明显加强,NMDA受体甘氨酸位点及胞内蛋白激酶系统参与了脊髓SP与NMDA受体的相互作用。     

人参皂甙Rg1对大鼠神经传递作用的机制研究

目的研究NMDA受体及电压依赖性钙通道在人参皂苷Rg1对麻醉大鼠海马神经传递的作用。方法采用胞外记录的方法观测在体麻醉大鼠齿状回群峰电位的幅度,观察AP5和尼莫地平对神经传递的影响。结果 AP5和尼莫地平对麻醉大鼠海马基础突触传递水平没有影响,但APV抑制了Rg1海马齿状回突触传递长时程增强的诱导,尼莫地平对于Rg1诱导的长时程增强没有影响。结论 Rg1所诱导的神经传递长时程增强为NMDA受体依赖性的,非VDCC依赖性。     

腺苷A1受体和NMDA受体在海马齿状回突触传递活动中的关系

目的　探讨腺苷A1受体阻断剂对海马齿状回 (DG)突触传递活动的影响及其与NMDA受体的关系。方法采用在体记录麻醉大鼠LTP的电生理学方法 ,观察腺苷A1受体特异性阻断剂 8 环戊 1,3 二丙基黄嘌呤 (DPCPX)与NMDA受体激动剂、阻断剂在海马DG基础突触传递活动和高频刺激诱导的LTP中作用的相关性。结果　DPCPX(6mg·L- 1,5μL ,icv)或NMDA(0 2mg·L- 1,5μL ,icv)不影响大鼠海马DG突触传递活动 ,DPCPX对icvNMDA后高频刺激诱导已形成的LTP维持也无影响 ;预先给予DPCPX后则可显著增强NMDA的海马DG基础突触传递活动和LTP ;AP5(0 5mg·L- 1,5μL)阻断NMDA受体后对LTP的抑制作用不受DPCPX的影响 ,但预先给予DPCPX则可取消AP5 对LTP的抑制作用。结论　DPCPX不影响海马DG突触传递活动 ,但可影响NMDA受体的效应 ,增强NMDA受体在海马DG突触传递活动中的作用     

脊髓NMDA受体在慢性内脏高敏大鼠中作用研究Ⅰ

目的从整体行为学角度探讨脊髓NMDA受体在慢性内脏高敏大鼠中的作用。方法选用SD大鼠,模型组大鼠在出生后d8~d15内,每天接受一次结直肠扩张刺激;对照组除了不行结直肠扩张刺激外,其他情况同模型组。大鼠成年后用腹壁撤退反射(AWR),进行肠道敏感性评估。观察两组鞘内注射MK-801前后AWR评分和腹外斜肌对结直肠扩张刺激的反应是否存在差异。结果①在20~60mm-Hg CRD时,模型组AWR评分明显高于对照组(P<0.05)。②鞘内注射不同浓度MK-801后,模型组AWR测痛阈呈剂量依赖性升高(P<0.05),而对照组没有表现出明显的剂量依赖性。③鞘内注射MK-801(1.5mol·L-1)后,模型组腹外斜肌对CRD反应较给药前明显降低(P<0.05),肌电测痛阈明显升高(P<0.05);而对照组给药前后无改变。④模型组结直肠病理检查未见明显病理性改变。结论大鼠脊髓NMDA受体可能参与慢性肠道高敏感机制。     

The role of CNS NMDA receptors and nitric oxide in visceral hyperalgesia.

The studies summarized here document the role of NMDA receptors and nitric oxide in the lumbosacral spinal cord and rostral ventromedial medulla in the maintenance of visceral hyperalgesia. Experiments were conducted in rats in which drugs were administered into either the lumbosacral intrathecal space or directly into the rostral ventromedial medulla. The visceral stimulus was noxious colorectal distension, administered before and 3 h after intracolonic instillation of either saline or 25% zymosan. The visceromotor response to colonic distension was quantified and found to be significantly enhanced in rats in which the colon had previously been treated with zymosan. Enhanced responses to distension were attenuated dose-dependently by intrathecal administration of the NMDA receptor channel blocker MK-801 and by inhibition of the neuronal isoform of nitric oxide synthase (nNOS). In corresponding studies wherein drugs were administered directly into the rostral ventromedial medulla, NMDA receptor antagonism and NOS inhibition dose-dependently attenuated exaggerated responses to colonic distension. Taken together, these data suggest that zymosan-produced visceral hyperalgesia is influenced both at the level of the spinal cord and rostral ventromedial medulla, and that descending facilitatory influences from the rostral ventromedial medulla are important to the maintenance of visceral hyperalgesia.     

Analgesic effect of paeoniflorin in rats with neonatal maternal separation-induced visceral hyperalgesia is mediated through adenosine A1 receptor by inhibiting the extracellular signal-regulated protein kinase (ERK) pathway

Paeoniflorin (PF), a chief active ingredient in the root of Paeonia lactiflora Pall (family Ranunculaceae), is effective in relieving colorectal distention (CRD)-induced visceral pain in rats with visceral hyperalgesia induced by neonatal maternal separation (NMS). This study aimed at exploring the underlying mechanisms of PF's analgesic effect on CRD-evoked nociceptive signaling in the central nervous system (CNS) and investigating whether the adenosine A₁ receptor is involved in PF's anti-nociception. Results: CRD-induced visceral pain as well as phosphorylated-extracellular signal-regulated protein kinase (p-ERK) and phospho-cAMP response element-binding protein (p-CREB) expression in the CNS structures of NMS rats were suppressed by NMDA receptor antagonist dizocilpine (MK-801) and ERK phosphorylation inhibitor U0126. PF could similarly inhibit CRD-evoked p-ERK and c-Fos expression in laminae I-II of the lumbosacral dorsal horn and anterior cingulate cortex (ACC). PF could also reverse the CRD-evoked increased glutamate concentration by CRD as shown by dynamic microdialysis monitoring in ACC, whereas, DPCPX, an antagonist of adenosine A₁ receptor, significantly blocked the analgesic effect of PF and PF's inhibition on CRD-induced p-ERK and p-CREB expression. These results suggest that PF's analgesic effect is possibly mediated by adenosine A₁ receptor by inhibiting CRD-evoked glutamate release and the NMDA receptor dependent ERK signaling.     

NMDA受体NR2B亚单位在慢性内脏痛觉敏化中的作用

目的探讨外周与脊髓NMDA受体NR2B亚单位在慢性内脏痛觉敏化中的作用。方法模型组大鼠出生后d8～15,每天接受一次伤害性结直肠扩张刺激,8wk龄后用腹壁撤退反射(AWR)评估大鼠肠道敏感性。对腰骶背根神经节及胸腰与腰骶脊髓背角神经元进行免疫组织化学染色,比较对照与模型大鼠NR2B的表达。并比较对照与模型两组大鼠腹腔注射AP-7(NMDA受体拮抗剂)前后原发传入神经对结直肠扩张刺激的反应。结果①模型组大鼠AWR评分显著增高。②模型大鼠脊髓背根神经节NR2B亚单位表达增强。③模型大鼠脊髓内脏相关神经元NR2B亚单位表达增强。④AP-7显著抑制模型大鼠腰骶传入神经纤维对结直肠刺激的反应。结论NMDA受体NR2B亚单位可能参与慢性内脏痛外周与脊髓痛觉敏化的过程。     

NMDA receptor antagonists block cardiovascular responses to intrathecal administration of D-baclofen in the rat.

In previous studies we found that D and L-baclofen have different effects on sympathetic output when administered intrathecally, yet the actions of both enantiomers are blocked by intrathecal administration of phaclofen. The present experiments were done to determine the mechanism by which D-baclofen expresses its effects. In urethane-anaesthetized Sprague-Dawley rats, when D-baclofen was given intrathecally at the T9 spinal level following pretreatment with 2 nmol of the NMDA receptor antagonist, DL-2-amino-5-phosphonovaleric acid (APV), it increased systolic and diastolic arterial pressures (n = 7), as in the previous studies. However, after intrathecal administration of 10 nmol of APV, administration of D-baclofen had no effect on these parameters (n = 7). Intravenous administration of ketamine (7.5 mg/kg), another NMDA receptor antagonist, also blocked the effect of D-baclofen (n = 6) but it had no effect on the pressor responses produced by intrathecal administration of carbachol (27.4 nmol; n = 6). In additional experiments, L-baclofen (70 nmol) had no effect on the increases in heart rate and arterial pressure produced by N-methyl-D-aspartic acid (NMDA) (2 nmol; n = 8). These results indicate that D-baclofen increases arterial pressure via an NMDA receptor-mediated mechanism, perhaps by provoking the release of an endogenous ligand which activates these receptors.     

Administration of AP5, a glutamate antagonist, unmasks glycine analgesic actions in the rat.

The effect of intrathecal (IT) injection of glycine alone or in combination with 2-amino-5-phosphonopentanoate (AP5) on two nociceptive tests--the vocalization threshold to tail-shock (VTTS) and the tail-flick latency (TFL)--was studied in ovariectomized Sprague-Dawley rats. IT injection of 400 micrograms glycine induced a nonsignificant decrease, that is, in comparison with saline, in both nociceptive thresholds. IT AP5 (10 micrograms) provoked a slight but significant increase in both nociceptive thresholds within the first 15 min postinjection. Combination of both glycine (400 micrograms) and AP5 (10 micrograms) produced marked and prolonged analgesia in both tests, which was significantly different from that obtained with AP5 alone. The results suggest that IT glycine acting through the strychnine-sensitive Gly1 receptor produces analgesia provided its effect on the Gly2 receptor linked to the NMDA receptor is prevented by an antagonist.     

Effect of zaldaride maleate, an antidiarrheal compound, on visceral pain reflex induced by small intestinal distention in anesthetized rats

Using distention of the small intestine as a visceral pain model, we investigated the effect of zaldaride maleate (ZAL), a selective inhibitor of calmodulin, on the depressor response. In pentobarbital-anesthetized rats, small intestine distention was induced by rapid application of intraluminal pressures of 40 cmH2O causing a reflex fall in arterial blood pressure. The depressor response to intestinal distention was abolished by intraperitoneal administration of capsaicin (5 mg/rat), which depletes neuropeptides such as substance P from the sensory neurons, on the mesenteric stalk and by neonatal pretreatment with capsaicin (50 mg/kg, s.c.). Morphine (20 mg/kg, s.c.) reduced the depressor response following intestinal distention. At doses of 3 mg/kg (i.v.) and higher, ZAL significantly reduced depressor response. The effect of morphine was reversed by naloxone (5 mg/kg, i.v.); the effect of ZAL was not affected. These results suggest that ZAL helps reduce the visceral pain induced by noxious stimulus and that the antinociceptive effect of ZAL is not mediated by opioid receptors.     

The antinociceptive effects of intravenous tianeptine in colorectal distension-induced visceral pain in rats: the role of 5-HT₃ receptors

Tianeptine is an unusual tricyclic antidepressant drug. In this study, we aimed to investigate the antinociceptive effect of tianeptine on visceral pain in rats and to determine whether possible antinociceptive effect of tianeptine is mediated by serotonergic (5-HT(2,3)) and noradrenergic (α(1,2)) receptor subtypes. Male Sprague Dawley rats (250-300 g) were supplied with a venous catheter, for drug administrations, and enameled nichrome electrodes, for electromyography, at external oblique musculature. Colorectal distension (CRD) was employed as the noxious visceral stimulus and the visceromotor response (VMR) to CRD was quantified electromyographically before and 5, 15, 30, 60, 90 and 120 min after tianeptine administration. Antagonists were administered 10 min before tianeptine for their ability to change tianeptine antinociception. Intravenous administration of tianeptine (2.5-20 mg/kg) produced a dose-dependent reduction in VMR. Administration of 5-HT(3) receptor antagonist ondansetron (0.5, 1 and 2 mg/kg), but not 5-HT(2) receptor antagonist ketanserine (0.5, 1 and 2 mg/kg), reduced the antinociceptive effect of tianeptine (10mg/kg). In addition, administration of α(1)-adrenoceptor antagonist prazosin (1 mg/kg) or α(2)-adrenoceptor antagonist yohimbine (1 mg/kg) did not cause any significant effect on the tianeptine-induced antinociception. Our data indicate that intravenous tianeptine exerts a pronounced antinociception against CRD-induced visceral pain in rats, and suggests that the antinociceptive effect of tianeptine appears to be mediated in part by 5-HT(3) receptors, but does not involve 5-HT(2) receptors or α-adrenoceptors.     

5-HT3-receptor antagonist inhibits visceral pain differently in chemical and mechanical stimuli in rats

The present study was designed to compare the effects of a selective 5-HT(3)-receptor antagonist, alosetron, on the glycerol-and colorectal distention (CRD)-induced visceral nociception as measured by changes in EMG of the external oblique muscle in conscious rats. Both glycerol and CRD evoked the EMG response, and these amplified EMG were attenuated by morphine, indicating that these responses might reflect visceral nociceptive responses. In the present study, we showed that alosetron significantly attenuated the glycerol-induced visceral pain, but not that of CRD. These results suggest that the mechanism of glycerol-induced visceral nociception are apparently different from that of CRD.     

Acetic acid conditioning stimulus induces long-lasting antinociception of somatic inflammatory pain

A wide variety of noxious stimuli are known to induce a powerful inhibition of pain sensation evoked at a remote region of the body. Here we show that an intraperitoneal acetic acid (AA) conditioning stimulus produces long-lasting inhibition of formalin-evoked somatic inflammatory pain behavior in mice. This novel long-lasting antinociception was completely blocked by the 5-hydroxytryptamine type 2A/2C (5-HT(2A/2C)) receptor antagonists, ketanserin and ritanserin, but not by the opioid receptor antagonist, naloxone, and alpha-adrenergic receptor antagonists, phentolamine and yohimbine. In contrast, the 5-HT(3/4) receptor antagonist, tropisetron, significantly potentiated this long-lasting antinociception. The conditioning stimulus significantly upregulated the levels of both tryptophan hydroxylase immunoreactivity in the medulla oblongata and the 5-HT(2A/2C) receptor mRNA level in the spinal cord. These results suggested that the visceral noxious stimulus caused a long-lasting augmentation of the serotonergic inhibitory system and downregulated the somatic inflammatory nociceptive transmission.