阿托品对褪黑素抑制猫丘脑后核群诱发放电的影响

目的研究M受体阻断剂阿托品对褪黑素(melatonin,MT)中枢镇痛作用的影响,进一步探索MT的作用机制。方法采用猫脑立体定位技术和玻璃微电极细胞外记录法,以刺激内脏大神经(GSN)诱发猫丘脑后核群(PO)单位放电为内脏痛指标,侧脑室给药,观察药效。结果0.1% MT(10 μg·kg^-1,icv)可明显抑制刺激GSN在PO诱发的单位放电,0.1%阿托品(20 μg,icv)可拮抗其对PO短潜伏期(58±22) ms诱发放电的抑制作用,而0.1%吗啡(5 μg,icv)对此潜伏期放电的抑制作用则不被等量的阿托品拮抗。结论MT有中枢镇痛作用,在此过程中可能有胆碱能神经的参与,MT的镇痛机制与吗啡存在着差异。     

纳络酮对褪黑素抑制猫丘脑后核群诱发放电的影响

目的研究阿片受体阻断剂纳络酮对褪黑素 (melatonin ,MT)中枢镇痛作用的影响 ,进一步探索MT的作用机制。方法采用猫脑立体定位技术和玻璃微电极细胞外记录法 ,以刺激内脏大神经(GSN)诱发猫丘脑后核群 (PO)单位放电为内脏痛指标 ,侧脑室给药 ,观察药效。结果侧脑室注射(icv) 4 3 0× 1 0 -3 mol·L-1MT 1 0 μg·kg-1可明显抑制刺激GSN在PO诱发的单位放电 ,2 75×1 0 -3 mol·L-1纳络酮 (5 0 μg,icv)可部分拮抗MT对PO诱发放电的抑制作用。结论MT有中枢镇痛作用 ,MT的镇痛作用与增加内源性阿片系统的活动有关     

侧脑室注射东莨菪碱对吗啡依赖大鼠戒断反应的抑制作用

目的 观察非选择性毒蕈碱（M）受体拮抗剂东莨菪碱、选择性M1受体拮抗剂哌拉唑嗪以及选择性M2受体拮抗剂美索四氨对吗啡戒断反应的影响。方法 采用吗啡依赖大鼠模型侧脑室注射上述药物,并用腹腔注射纳洛酮诱发戒断反应,记录60min内戒断症状。结果 侧脑室注射东莨菪碱（25,50μg)、派拉唑嗪（20μg)和美索四氨（25μg)可明显抑制由纳洛酮诱发戒断反应,东莨菪碱减轻吗啡戒断症状呈明显量效关系。结论 侧脑室注射东莨菪碱能减轻吗啡戒断反应,提示中枢胆碱能神经毒碱（M）受体在吗啡依赖和耐受过程中起重要作用。     

5-HT1A受体激动剂乌拉地尔对吗啡依赖大鼠戒断反应的抑制作用

目的··：观察５－ＨＴ１Ａ受体激动剂乌拉地尔（ｕｒａｐｉｄｉｌ）和８－ＯＨ－ＤＰＡＴ及阿片μ受体激动剂美沙酮（ｍｅｔｈａｄｏｎｅ）对吗啡戒断反应的影响。方法··：采用吗啡依赖大鼠模型侧脑室注射上述药物,并用腹腔注射纳洛酮诱发戒断反应,记录戒断症状。结果··：侧脑室注射乌拉地尔可明显抑制纳洛酮诱发的吗啡躯体戒断反应,并呈量效关系。乌拉地尔抑制吗啡戒断反应的作用与８－ＯＨ－ＤＰＡＴ的作用一致。此效应与美沙酮的作用相比也基本相同。结论··：乌拉地尔通过激活５－ＨＴ１Ａ受体可以抑制吗啡戒断反应。     

5-HT_(1A)受体激动剂乌拉地尔对吗啡依赖大鼠戒断反应的抑制作用

目的··：观察５－ＨＴ１Ａ受体激动剂乌拉地尔（ｕｒａｐｉｄｉｌ）和８－ＯＨ－ＤＰＡＴ及阿片μ受体激动剂美沙酮（ｍｅｔｈａｄｏｎｅ）对吗啡戒断反应的影响。方法··：采用吗啡依赖大鼠模型侧脑室注射上述药物,并用腹腔注射纳洛酮诱发戒断反应,记录戒断症状。结果··：侧脑室注射乌拉地尔可明显抑制纳洛酮诱发的吗啡躯体戒断反应,并呈量效关系。乌拉地尔抑制吗啡戒断反应的作用与８－ＯＨ－ＤＰＡＴ的作用一致。此效应与美沙酮的作用相比也基本相同。结论··：乌拉地尔通过激活５－ＨＴ１Ａ受体可以抑制吗啡戒断反应。     

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。     

侧脑室注射钩藤碱增加大鼠心血管相关核团中c-fos的表达

目的研究侧脑室注射钩藤碱（Rhy）对大鼠脑内心血管相关核团中c-fos表达的影响。方法应用Fos蛋白免疫组化技术。结果侧脑室注射Rhy诱发脑干的延髓头端腹外侧核（RVL）、蓝斑核（LC）、旁巨细胞外侧核（iPGL）,下丘脑的室旁核（PVN）、视上核（SON）等多个部位的心血管中枢出现大量Fos样免疫反应（FLI）神经元。L型-钙通道开放剂Bayk 8644可明显减弱Rhy的效应。蛋白酪氨酸磷酸酶抑制剂正矾酸钠也可明显减弱Rhy的效应。结论Rhy可兴奋脑内多个心血管相关核团的神经元,其机制可能与阻断神经元上的钙通道并进而抑制蛋白质磷酸化有关。     

褪黑素对猫丘脑后核内脏痛放电的影响

目的观察静脉注射不同剂量褪黑素 (melatonin ,MT)对猫丘脑后核 (PO)诱发放电的影响及其存在的昼夜节律变化。方法本实验采用猫脑立体定位技术和玻璃微电极细胞外记录的方法 ,以刺激内脏大神经 (GSN)诱发PO单位放电作为内脏痛指标。结果静脉注射 1 0、1 5、2 0、2 5mg/kgMT对刺激GSN诱发的PO单簇放电均有抑制作用 ,随剂量的增大 ,抑制作用增强。对于相同的给药剂量 ( 1 5mg/kg) ,下午的镇痛时间明显较上午长 ,且存在统计学差异。 结论首次发现MT在丘脑后核水平参与抑制内脏痛 ,此抑制作用存在剂量依赖关系 ,并具有昼夜节律变化。     

蜂毒诱发大鼠结肠炎疼痛实验模型的建立

目的建立蜂毒诱发大鼠结肠炎疼痛实验模型,用于镇痛药的评价及相关机理研究。方法利用蜂毒结肠粘膜下注射诱发大鼠结肠炎疼痛,动态定量评价大鼠的疼痛行为学反应,并进行组织学检查,同时与甲醛相比较。结果每只大鼠结肠粘膜下注射蜂毒0.075,0.15和0.3mg可剂量依赖性地诱发大鼠持续性内脏痛,与5%甲醛(0.1mL)相比,蜂毒0.3mg致痛反应效应相当,第二相炎症反应明显,且持续期长;局部组织损伤轻。阿片类镇痛药吗啡、解热镇痛药阿司匹林和新型环氧合酶2抑制剂NS-398均能抑制蜂毒诱发的大鼠结肠炎疼痛。结论蜂毒诱发大鼠结肠炎疼痛模型反应指标客观、实验重复性好,是一种较理想的内脏疼痛实验模型,可用于镇痛药的评价及机理研究。     

鞘内注射氯胺酮对内脏痛大鼠远位触液神经元Fos蛋白表达的影响

目的观察鞘内注射氯胺酮对内脏痛大鼠远位触液神经元(dCSF-CN)Fos蛋白表达的影响。方法 SD大鼠侧脑室注射霍乱毒素亚单位B与辣根过氧化物酶复合物(CB-HRP)示踪标记dCSF-CN。48h后氯胺酮(K)组(n=10)鞘内注射氯胺酮50μg,人工脑脊液(C)组(n=10)鞘内注射等体积人工脑脊液。两组均在乙状结肠壁注射甲醛制作内脏痛模型。进行各时间点疼痛学评分,免疫组织化学法检测Fos蛋白在dCSF-CN中的表达。结果与C组相比,K组大鼠各时间点疼痛学评分降低(P<0.01),dCSF-CN中Fos蛋白表达下降(P<0.01)。K组未见CB-HRP/Fos双标记神经元。结论鞘内注射氯胺酮可以降低大鼠内脏痛反应,减少dCSF-CN中Fos蛋白的表达。     

CNQX对电刺激隐神经诱发大鼠扣带回前部神经元c-Fos基因表达的影响

目的阐明伤害性电刺激隐神经(saphenous nerve,SN)能否引起扣带回前部(anterior cingulategyrus,ACG)神经元c-Fos基因表达及其发生机制。方法用免疫组化方法研究伤害性电刺激SN后不同时间,ACG神经元c-Fos基因表达的变化,以及尾静脉注射α-氨基3-羟基5-甲基4-异恶唑丙酸/海人藻氨酸(α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid/kainate,AMPA/kainate)受体拮抗剂受体是谷氨酸受体之一,6-氰基-7-硝基喹喔啉-2,3-二酮(6-cyano-7-nitroquinoxaline-2,3-dike-tone,CNQX)对该变化的影响。结果伤害性电刺激SN后30 min ACG神经元Fos蛋白表达明显增加,60 min增加最明显,120 min后开始消退;并且尾静脉注射CNQX拮抗了伤害性电刺激SN引起的ACG神经元Fos蛋白表达的显著增加。结论伤害性电刺激SN能够引起ACG神经元Fos蛋白表达的显著增加,这种表达呈时间依赖性,提示ACG存有SN代表区,能够感受SN传入的伤害性信息;CNQX拮抗了伤害性电刺激SN引起的ACG神经元Fos蛋白表达的显著增加,提示AMPA/kainate受体参与此过程。     

The rostral ventromedial medulla mediates the facilitatory effect of microinjected orphanin FQ in the periaqueductal gray on spinal nociceptive transmission in rats

Single unit extracellular recordings from spinal dorsal horn neurons were obtained with glass micropipettes in pentobarbital-anesthetized rats. A total of 50 wide dynamic range (WDR) neurons were studied in 25 rats. Microinjection of orphanin FQ (OFQ, 0.1 microg/0.1 microl) (a potent endogenous ligand of the opioid receptor-like receptor (ORL-1)) into the ipsilateral ventrolateral parts of periaqueductal gray (vlPAG) significantly increased C-response and post-discharge activity in most of the WDR neurons. Pre-microinjection of lidocaine (4%) into the nucleus raphe magnus (NRM) (0.5 microl), ipsilateral nucleus reticularis gigantocellularis (NGC) (0.6 microl), or nucleus gigantocellularis pars alpha (NGCalpha) and nucleus reticularis paragigantocellularis lateralis (NPGL) (0.5 microl) markedly reduced intra-vlPAG microinjection of OFQ-induced facilitatory effects on nociceptive responses of WDR neurons. Furthermore, if the NRM and ipsilateral NGC were simultaneously pre-microinjected with lidocaine, the intra-vlPAG microinjection of OFQ-induced facilitation on nociceptive responses of WDR neurons was eliminated. Also, a similar effect was observed when all the NRM, ipsilateral NGC, NGCalpha and NPGL were blocked with lidocaine. No significant effect on nociceptive responses of WDR neurons per se was found after blocking the NRM, ipsilateral NGC, NGCalpha/NPGL, or all the NRM, ipsilateral NGC, and NGCalpha/NPGL with lidocaine. These results indicate that (1) the facilitatory effect evoked by microinjection of OFQ into the vlPAG on nociceptive responses of WDR neurons in the spinal dorsal horn is primarily mediated by the NRM and ipsilateral NGC; (2) the NRM, ipsilateral NGC, and NGCalpha/NPGL do not mediate tonic descending inhibition of the spinal dorsal horn neurons.     

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.     

The role of spinal muscarinic acetylcholine receptors in clonidine-induced anti-nociceptive effects in rats

We have examined the effects of intrathecal (i.t.) injection of the muscarinic acetylcholine receptor antagonist atropine on the clonidine-induced nociceptive effect in formalin-induced nociception in rats. The injection of 5% formalin into the hind paw caused biphasic nociceptive responses, and i.t. injection of clonidine inhibited both phases of the nociceptive response in a dose-dependent manner. Pretreatment with atropine (i.t.) only partially inhibited the nociceptive effect of clonidine. These results suggest that the nociceptive effect of clonidine in the rat formalin model may be at least partly mediated by muscarinic acetylcholine receptors in the spinal cord.     

Role of peripheral purinoceptors in the development of bee venom‐induced nociception: A behavioural and electrophysiological study in rats

Colocalization of purinergic P2X and P2Y receptors in dorsal root ganglion sensory neurons implies that these receptors play an integrative role in the nociceptive transmission process under inflammatory conditions. In the present study, behavioural and in vivo electrophysiological methods were used to examine the peripheral role of P2 receptors in the persistent nociceptive responses induced by subcutaneous bee venom injection (2 mg/mL) in. Sprague‐Dawley rats Local pretreatment with the wide‐spectrum P2 receptor antagonist pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS; 1 mmol/L, 50 μL) 10 min prior to s.c. bee venom injection significantly suppressed the duration of spontaneous nociceptive lifting/licking behaviour, inhibited mechanical hyperalgesia and decreased the firing of spinal dorsal horn wide dynamic range neurons in response to bee venom, without affecting primary thermal and mirror‐image hyperalgesia. The localized antinociceptive action of PPADS was not due to a systemic effect, because application of the same dose of PPADS to the contralateral side was not effective. The results suggest that activation of peripheral P2 receptors is involved in the induction of nociceptive responses, mechanical hyperalgesia and the excitation of sensory spinal neurons.     

Participation of brainstem nuclei in the pronociceptive effect of lesion or neural block of the anterior pretectal nucleus in a rat model of incisional pain

The anterior pretectal nucleus (APtN) participates in nociceptive process and controls spinal nociceptive inputs, and its integrity reduces the severity of the responses to persistent injury. In this study we examined whether the pedunculopontine tegmental nucleus (PPTg) or the gigantocellularis nucleus pars alpha (GiA), stations that relay APtN inputs to the spinal cord, can control the persistent pain induced by a hind paw incision in rats with disrupted APtN. The withdrawal threshold to mechanical stimulation of the incised paw measured with von Frey filaments was significantly reduced in rats with contralateral APtN lesion or neural block of this nucleus with 2% lidocaine. Intrathecal xylamine, an inhibitor of noradrenaline uptake, inhibited the neural block of the APtN-induced increase in the incisional pain. Injection of glutamate into the contralateral PPTg or ipsilateral GiA reduced the incisional pain. Neural block of the PPTg or GiA reduced the threshold, mainly in APtN-disrupted rats. We conclude that persistent noxious stimulation activates descending pathways involving the contralateral APtN and PPTg, and ipsilateral GiA. Disruption of the APtN allows the activation of alternative circuitry involving at least the PPTg and GiA as intermediary stations that might maintain the control of nociceptive inputs in the spinal cord, probably involving noradrenergic mechanisms.     

Evaluation of opioid-induced antinociceptive effects in anaesthetized and conscious animals

1. The activity profiles of opioid agonists and non-steroidal analgesic agents have been compared against different nociceptive stimuli in the mouse and rat. 2. Opioid agonists, but not non-steroidal analgesic agents, inhibited reflex depressor responses evoked by visceral distension in anaesthetized rats. The ranked order of potency of opioids in the visceral distension reflex was identical to that observed in the mouse writhing assay. 3. Opioid-induced inhibition of reflex depressor responses and writhing was observed with ligands acting on mu- and kappa-, but not delta-receptors. Antinociceptive activity of opioids in the rat cold water tail-flick assay was restricted to mu-receptor agonists. 4. Morphine- and ethylketocyclazocine (EKC)-induced inhibition of the visceral distension reflex was blocked by naloxone, but not by the quaternary opioid antagonist N-methylnalorphine. 5. Direct cardiovascular effects were observed with ligands for the mu- and kappa-receptor. Blood pressure changes induced by morphine and Tyr.D-Ala.Gly.MePhe.Gly-ol (DAGOL), but not EKC, were blocked by N-methylnalorphine. Pretreatment with 16-methylcyprenorphine (M8008) antagonized morphine-, DAGOL- and EKC-induced cardiovascular effects, but not those of dynorphin-(1-13) or U50488. 6. It is concluded that reflex circulatory responses evoked by visceral distension in anaesthetized rats are a valid index for the evaluation of opioid-induced antinociception. A simultaneous assessment of cardiovascular effects of opioids was achieved.