强啡肽对脊髓原生型与诱生型一氧化氮合成酶活性、分布和基因表达的影响及机制

蛛网膜下腔注射（ｉ．ｔ．）强啡肽Ａ１－１７（Ｄｙｎ）引起剂量依赖性后肢和尾部瘫痪及甩尾甩足抑制。脊髓背角（侧）ＮＭＤＡ受体和ＮＯＳ／ＮＯ功能活性下降可能与Ｄｙｎ镇痛作用有关,脊髓腹角（侧）ＮＭＤＡ受体－Ｃａ２＋－ＮＯＳ／ＮＯ通路过度激活及ｃ－ｆｏｓ高表达可能与Ｄｙｎ致脊髓损伤（ＳＣＩ）作用有关。在Ｄｙｎ致ＳＣＩ机制中,过量ＮＯ（细胞水平）具有神经毒性作用,脑源性ＮＯＳ主要在早期,诱生型ＮＯＳ主要在后期起作用,而内皮细胞源性ＮＯＳ和适量ＮＯ（血管水平）可能具有保护作用。在原代培养脊髓神经元中,高浓度Ｄｙｎ可通过ＮＭＤＡ受体和κ受体直接引起细胞内Ｃａ２＋超负荷,低浓度Ｄｙｎ只通过κ受体抑制高钾刺激性Ｃａ２＋内流     

内皮素受体反义寡聚核苷酸对内皮素受体基因表达及血管平滑肌细胞增殖的影响

报道了内皮素Ａ型受体反义寡聚核苷酸（ＯＤＮｓ）对大鼠血管平滑肌细胞（ＶＳＭＣ）增殖及内皮素受体基因表达的影响．~３Ｈ－ＴｄＲ参入结果显示,内皮素Ａ型受体反义ＯＤＮｓ处理细胞可显著抑制内皮素诱导的ＶＳＭＣ的ＤＮＡ合成,反转录－ＰＣＲ及受体结合实验结果表明,ＯＤＮｓ的上述作用与降低ＶＳＭＣ内皮素Ａ型受体基因表达活性有关．     

氯氨酮和L-NAME抑制模拟高原低氧大鼠下丘脑NOS和生长抑素mRNA的表达

用高原低氧模型及原位杂交、ＮＡＤＰＨ－ｄ组织化学法,探讨氯氨酮和Ｌ－ＮＡＭＥ对急性高原低氧大鼠下丘脑一氧化氮合酶（ＮＯＳ）和生长抑素ｍＲＮＡ（ＳＳ ｍＲＮＡ）表达的影响。结果表明,急性高原低氧引起下丘脑ＮＯＳ和ＳＳ ｍＲＮＡ过度表达,如先用ＮＭＤＡ受体拮抗剂氯氨酮和ＮＯＳ抑制剂Ｌ－ＮＡＭＥ预处理,ＮＯＳ和ＳＳ ｍＲＮＡ的表达均明显被抑制。结果提示,ＮＭＤＡ受体参与了急生高原低氧引起的下丘脑ＮＯＳ和     

青心酮对妊娠高血压综合征胎盘血管内皮和平滑肌细胞内一氧化氮合酶的影响

本文对正常孕妇、妊娠高血压综合征（ＰＩＨ）患者和经青心酮（ＤＨＡＰ）治疗的ＰＩＨ患者等共２４例,应用组织化学分析方法观察胎盘血管内皮细胞（ＶＥＣ）和平滑肌细胞（ＶＳＭＣ）内一氧化氮合酶（ＮＯＳ）活性的变化。结果表明：正常孕妇胎盘ＶＥＣ和ＶＳＭＣ内ＮＯＳ活性较高;ＰＩＨ胎盘ＶＥＣ和ＶＳＭＣ内ＮＯＳ活性明显减弱,并伴有组织和细胞的形态学损伤;经ＤＨＡＰ治疗后的ＰＩＨ胎盘ＶＥＣ和ＶＳＭＣ细胞ＮＯＳ活性较未经ＤＨＡＰ治疗者明显增加,其组织和细胞损伤也减轻。本研究结果提示胎盘内ＶＥＣ和ＶＳＭＣ细胞的ＮＯＳ减少可能与ＰＩＨ的发生和／或发展有关,青心酮治疗ＰＩＨ的作用可能与ＤＨＡＰ促进胎盘ＶＥＣ和ＶＳＭＣ内一氧化氮（ＮＯ）合成有关。     

实验性癫痫时海马内一氧化氮合酶的变化及其与谷氨酸受体的关系

应用免疫组织化学方法观察了青霉素致痫时海马内神经元型一氧化氮合酶（ｎＮＯＳ）表达的时程变化及海马内微量注射ＮＭＤＡ受体拮抗剂ＭＫ－８０１（５－ｍｅｔｈｙｌ－１０,１１－ｄｉｈｙｄｒｏ－５Ｈ－ｄｉｂｅｎｚｏ［ａ,ｄ］ｃｙｃｌｏｈｅｐｔａｎ－５,１０－ｉｍｉｎｅｍａｌｅａｔｅ）和非ＮＭＤＡ受体拮抗剂ＤＮＱＸ（６,７－ｄｉｎｉｔｒｏｑｕｉｎｏｘａｌｉｎｅ－２,３－ｄｉｏｎｅ）对大鼠海马内ｎＮＯＳ表达的影     

晚妊人胎脊髓内一氧化氮合酶阳性神经元和阳性纤维的分布及其生物学意义

取７例人胎脊髓标本,用还原型辅酶Ⅱ（β－ＮＡＤＰＨ）组织化学方法对人胎脊髓内一氧化氮合酶（ＮＯＳ）阳性神经元和阳性纤维的分布进行了观察。ＮＯＳ阳性神经元在妊娠３２周至３９周胎龄人胎脊髓内的分布和细胞形态无明显差异,主要位于后角深层（Ⅲ、Ⅳ层）、中央管周围灰质和中间带外侧核（ＩＭＬ）;前角内可见少数散在的ＮＯＳ阳性神经元;在脊髓白质内有密集的ＮＯＳ阳性的胶质样细胞分布。ＮＯＳ阳性纤维主要见于后角浅层（Ⅰ、Ⅱ层）和中间带。脊髓内ＮＯＮ阳性神经元和阳性纤维的分布,提示脊髓内ＮＯＳ可能与内脏活动的调节和躯体感觉传入的调制有关;ＮＯＳ阳性的胶质样细胞可能参与白质内神经纤维的髓化过程。     

关于平列型气孔定义的讨论

关于平列型气孔定义的讨论汪乐原（湖北药检高等专科学校,武汉４３００６４）ＡＤＩＳＣＵＳＳＩＯＮＯＮＴＨＥＤＥＦＩＮＩＴＩＯＮＳＯＦＰＡＲＡＣＹＴＩＣＳＴＡＭＡＴＡＷａｎｇＬｅ－ｙｕａｎ（ＨｕｂｅｉＤｒｕｇＣｏｎｔｒｏｌａｎｄＭｅｄｉｃａｌＥｘａｍｉｒ...     

硫代反义寡核苷酸在细胞培养内抗甲型流感病毒活性

为了研究抗流感病毒特异性反义核酸药物,针对Ａ型流感病毒基因组３＇和５＇端保守序列,设计并合成了４条硫代寡核苷酸（ＯＤＮ）：３＇端反义ＯＤＮ（ＩＶ３＾＃）与３＇端正义ＯＤＮ（ＩＶ３Ｓ）,５＇端反义ＯＤＮ（ＩＶ４＾＃）与５＇端正交ＯＤＮ（ＩＶ４Ｓ）。以流感病毒血凝滴度和致细胞病变作用为指标,测定了ＯＤＮｓ在ＭＤＣＫ细胞中对Ａ型流感病毒Ａ／京防／８６－１（Ｈ１Ｎ１）复制的影响。结果表明,与流感病毒基因组     

肺血管EDNO及其合酶在大鼠低氧性肺动脉高压形成中的作用

本研究观察了低氧对大鼠肺组织和血管内皮一氧化氮合酶（ＮＯＳ）活性及内皮衍生一氧化氮（ＥＤＮＯ）依赖性舒张反应的影响,以及ＮＯＳ抑制剂（Ｌ－ＮＡＭＥ）对常氧和低氧大鼠肺组织和血管内皮ＮＯＳ活性及颈、肺动脉血压（ＣＡＰｓ、ｍＰＡＰ）的作用。结果表明常氧大鼠肺泡内无肌性血管内皮未见ＮＯＳ活性,其肺血管床对ＥＤＮＯ依赖性舒血管物质ＢＫ没有反应,注射Ｌ－ＮＡＭＥ后大鼠ｍＰＡＰ略有降低,ＣＡＰｓ有所升高。低氧大鼠肺泡内无肌性血管内皮显示ＮＯＳ活性,对ＢＫ的ＥＤＮＯ依赖性舒张反应呈剂量依赖性增大,注射Ｌ－ＮＡＭＥ使低氧大鼠ｍＰＡＰ显著降低（Ｐ＜０．０１）,ＣＡＰｓ显著升高（Ｐ＜０．０５）。提示肺血管ＥＤＮＯ及其合酶在维持正常成年大鼠肺循环低压低阻中的生理作用值得进一步探讨;低氧引起肺血管内皮ｅｃＮＯＳ活性增加和ＥＤＮＯ生成增多可能起到限制肺动脉压过度升高的调制作用,也可能对肺血管内皮产生毒性作用,反而促进肺动脉高压的发生和发展。     

中缝大核在刺激视上核镇痛中的作用

运用核团灌流液的放免测定和高压液相色谱法以及核团内注射拮抗剂,观察了化学刺激下丘脑视上核（ＳＯＮ）对中缝大核（ＮＲＭ）灌流液内催产素（ＯＴ）、精氨酸加压素（ＡＶＰ）和５－羟色胺（５－ＨＴ）含量的影响以及ＮＲＭ内注射ＡＶＰ、５－ＨＴ或ＯＴ受体拮抗剂对痛阈（ＰＴ）的影响。结果表明：ＳＯＮ内注射Ｌ－谷氨酸（Ｌ－Ｇｌｕ）１０μｇ后动物痛阈明显升高,ＮＲＭ灌流液中ＯＴ和５－ＨＴ的含量明显高于对照组水平,ＡＶＰ的含量仅有一过性增加。ＮＲＭ内注射ｏＴ或５－ＨＴ拮抗剂可逆转化学刺激ＳＯＮ引起的镇痛作用;而ＡＶＰ的Ｖ＿(１／２)受体拮抗剂也轻度抑制这种镇痛作用,但Ｖ＿１拮抗剂对此作用无影响。以上结果提示：在刺激ＳＯＮ镇痛中,ＯＴ起着重要作用,Ｌ－Ｇｌｕ刺激ＳＯＮ的ＯＴ细胞释放ＯＴ,作用于ＮＲＭ细胞的ＯＴ受体和Ｖ＿２受体而产生镇痛作用,５－ＨＴ在此过程中也发挥重要作用。     

Involvement of kappa/dynorphin system in the development of tolerance to nicotine-induced antinociception

The aim of the present study was to explore the possible role of kappa/dynorphin system in the development of tolerance to nicotine antinociception in mice. First, we observed that kappa-opioid receptor (KOP-r) participates in the acute spinal antinociception produced by nicotine (3 and 5 mg/kg, s.c.) since the pre-treatment with the selective kappa antagonist nor-binaltorphimine (3 mg/kg, i.p.) attenuated this response in the tail-immersion test but not in the hot-plate test nor in locomotor responses. Possible changes in the expression of KOP-r were investigated in tolerant mice to nicotine antinociception by using autoradiography of [³H]CI-977 binding. The density of KOP-r decreased in the spinal cord of tolerant mice. In addition, bi-directional cross-tolerance between nicotine (3 and 5 mg/kg, s.c.) and the selective kappa agonist U50,488H (10 mg/kg, s.c.) was found in the tail-immersion test. Recent evidences indicate that an up-regulation of dynorphin levels in the spinal cord and subsequent activation of NMDA receptors participate in the development of tolerance to opioid and cannabinoid antinociception. In this study, dynorphin content in the lumbar spinal cord was similar in control and nicotine tolerant mice. Furthermore, the administration of the NMDA antagonist MK-801 (0.03 and 0.01 mg/kg, i.p.) before each daily nicotine injection did not modify the development of nicotine tolerance. In summary, these data indicate that KOP-r is directly involved in the development of tolerance to nicotine antinociception by a mechanism independent from dynorphin and NMDA receptors.     

NMDA receptor antagonism produces antinociception which is partially mediated by brain opioids and dopamine.

Inhibition of nitric oxide synthase (NOS) activity results in opioid-mediated supraspinal analgesia in the rat, as indicated by increased reaction time in the hot plate test. It is documented that a relationship exists between NMDA receptor activation and the activity of NOS. The present investigation sought to determine if inactivation of the NMDA receptor produced antinociception of supraspinal origin, as was observed in response to inhibition of NOS, and if this response was mediated by brain opioids, by activation of receptors for the neurotransmitter, dopamine, or both. Administration of MK-801, a non-competitive antagonist of the NMDA receptor, produced significant antinociception as measured by reaction time in the hot plate test of analgesia. Antinociception resulting from treatment with MK-801 appeared to be mediated by brain opioids, as indicated by the ability of the opioid antagonist, naloxone, to partially reverse the effect of MK-801 administration. This analgesic response was also partially diminished by administration of the dopamine D1 receptor antagonist, SCH 23390 and the dopamine D2 receptor antagonist, sulpiride. The analgesia resulting from NMDA receptor antagonism was found to be only partially attributable to dopamine and brain opioids, since co-administration of naloxone and SCH 23390 or naloxone and sulpiride, were unable to completely reverse the antinociceptive response to MK-801. The present findings suggest that inhibition of NMDA receptor activity produces supraspinal analgesia. Furthermore, it appears that antinociception induced by blockade of the NMDA receptor results, at least in part, from activation of endogenous brain opioids and stimulation of D1 and D2 subtypes of the dopamine receptor.     

强啡肽A和CCK—8对大鼠脊髓突触小体摄取^45Ca的影响

为了探讨血管紧张素Ⅱ(AⅡ)和八肽胆囊收缩素(CCK-8)这两种肽的抗阿片作用机理,本实验中观察了三种阿片类物质(吗啡、强啡肽和 DPDPE)和两种抗阿片物质(AⅡ和 CCK-8)对大鼠脊髓突触小体摄取~(45) Ca 的影响。结果表明:(1)在脊髓腹柱突触小体上,10nmol/L—1μmol/L 的吗啡、强啡肽 A(Dyn A)和 DPDPE 对~(45)Ca 摄取均有较弱的抑制作用;(2)CCK-8在浓度高达lμmol/L 时对~(45)Ca 摄取有较弱的抑制作用;(3)AⅡ在浓度高达lμmol/L时也不影响腹柱突触小体摄取~(45)Ca;(4)在背柱的突触小体制备中,上述阿片物质中 Dyn A 对~(45)Ca 摄取有较强的抑制作用,并被 k 受体阻断剂 nor-BNI 所阻断。10和100nmol/L 的 CCK-8能翻转lμmol/L Dyn A 对~(45)Ca 摄取的抑制作用;(5)A Ⅱ不能翻转Dyn A 的抑制作用。以上结果提示,CCK-8阻断 Dyn A 抑制脊髓背柱突触小体摄取 Ca~(2+)的作用可能是其行为学中抗阿片作用的机理之一。AⅡ对脊髓 Ca~(2+)摄取和 Dyn A 抑制脊髓 Ca~(2+)摄取的作用皆无影响,与行为学中观察到的 AⅡ在脊髓内不能对抗阿片镇痛的现象一致,进一步说明 CCK-8和AⅡ拮抗阿片类物质对神经末梢 Ca~(2+)摄取的影响可能是其抗阿片作用的重要机理之一。     

Characterization of intrathecal vasopressin-induced antinociception, scratching behavior, and motor suppression.

Intrathecal (IT) administration of vasopressin produces antinociception, scratching behavior, and motor suppression. The present experiments characterized these effects with regards to the following: 1) VP receptor specificity, 2) possible involvement of endogenous opiates, 3) possible involvement of seizure activity, and 4) whether the antinociception is due to direct actions of VP at the spinal cord. These studies showed that IT administration of a V1-specific vasopressin antagonist completely blocked the antinociception, scratching behavior, and motor suppression produced by 25 ng IT vasopressin. Furthermore, IT administration of the vasopressin metabolite, [pGlu4,Cyt6]AVP(4-9), produced none of the effects produced by vasopressin. Systemic administration of the opiate antagonists naloxone (1 mg/kg IP) and naltrexone (10 mg/kg IP) had no significant effect on the antinociception produced by IT vasopressin, whereas naltrexone potentiated the scratching behavior. Neither the IT vasopressin-induced antinociception nor scratching behavior was affected by pretreatment with the anticonvulsant sodium valproate. In addition, IT vasopressin inhibited the tail flick reflex in rats with transected spinal cords, demonstrating direct spinal effects of vasopressin. In conclusion, IT administration of vasopressin produces antinociception, scratching behavior, and motor suppression via activation of VP-specific receptors in the spinal cord.     

Involvement of spinal metabotropic glutamate receptor 5 in the development of tolerance to morphine-induced antinociception

It is well known that prolonged exposure to morphine results in tolerance to morphine-induced antinociception. In the present study, we found that either intrathecal (i.t.) or subcutaneous (s.c.) injection of the selective metabotropic glutamate receptor 5 (mGluR5) antagonist, methyl-6-(phenylethynyl)-pyridine hydrochloride (MPEP), attenuated the development of tolerance to morphine-induced antinociception. Using the receptor binding assay, we found here that the number of mGluR5 in the mouse spinal cord was significantly increased by repeated treatment with morphine. Furthermore, repeated treatment with morphine produced a significant increase in the level of mGluR5 immunoreactivity in the dorsal horn of the mouse spinal cord. Double-labeling experiments showed that the increased mGluR5 was predominantly expressed in the neurons and sparsely expressed in the processes of astrocytes following repeated treatment with morphine. Consistent with these results, the response of Ca2+ to the selective group I mGluR agonist, 3,5-dihydroxyphenylglycine (DHPG), in cultured spinal cord neurons was potently enhanced by 3 days of in vitro treatment with morphine. These findings support the idea that the increased mGluR5 following repeated treatment with morphine leads to enhanced neuronal excitability and synaptic transmission in the dorsal horn of the spinal cord and, in turn, suppresses the morphine-induced antinociception in mice.     

Expression of nitric oxide synthase isoforms in the dorsal horn of monoarthritic rats: effects of competitive and uncompetitive <Emphasis Type="Italic">N</Emphasis>-methyl-D-aspartate antagonists

Chronic pain is associated with N-methyl-D-aspartate (NMDA) receptor activation and downstream production of nitric oxide, which has a pivotal role in multisynaptic local circuit nociceptive processing in the spinal cord. The formation of nitric oxide is catalyzed by three major nitric oxide synthase (NOS) isoforms (neuronal, nNOS; inducible, iNOS; endothelial, eNOS), which are increased in the spinal cord of rodents subjected to some tonic and chronic forms of experimental pain. Despite the important role of NOS in spinal cord nociceptive transmission, there have been no studies exploring the effect of NMDA receptor blockade on NOS expression in the dorsal horn during chronic pain. Furthermore, NOS isoforms have not been fully characterized in the dorsal horn of animals subjected to arthritic pain. The aim of this work was therefore to study the expression of nNOS, iNOS and eNOS in the dorsal horns of monoarthritic rats, and the modifications in NOS expression induced by pharmacological blockade of spinal cord NMDA receptors. Monoarthritis was produced by intra-articular injection of complete Freund's adjuvant into the right tibio-tarsal joint. At week 4, monoarthritic rats were given either the competitive NMDA antagonist (±)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) or the uncompetitive NMDA antagonist ketamine. After 6 and 24 hours, animals were killed and posterior quadrants of the lumbar spinal cord were dissected. Sample tissues were homogenized and subjected to immunoblotting with anti-nNOS, anti-iNOS or anti-eNOS monoclonal antibodies. The nNOS isoform, but not the iNOS and eNOS isoforms, were detected in the dorsal horns of control rats. Monoarthritis increased the expression of nNOS, iNOS and eNOS in the dorsal horns ipsilateral and contralateral to the inflamed hindpaw. Intrathecal administration of CPP and ketamine reduced nNOS expression in monoarthritic rats but increased the expression of iNOS and eNOS. Results suggest that blockade of spinal cord NMDA receptors produces complex regulatory changes in the expression of NOS isoforms in monoarthritic rats that may be relevant for nitridergic neuronal/glial mechanisms involved in the pathophysiology of monoarthritis and in the pharmacological response to drugs interacting with NMDA receptors.     

Modulation of NMDA receptors by AKT kinase

The aim of the present work was to assess whether Akt modulates NMDA receptor function in cerebellar neurons in culture. Forskolin increases cAMP and activates Akt and NMDA receptors. In neurons treated with forskolin, intracellular calcium increased to 296 +/- 38% and this was completely prevented by inhibition of Akt. This indicates that, in these neurons, cAMP modulates NMDA receptors via Epac and Akt. Brain derived neurotrophic factor (BDNF) increases phosphorylation (and activity) of Akt to 350 +/- 60% of basal and also potentiates the increase of calcium and in cGMP induced by NMDA. BDNF-induced potentiation of NMDA receptor function is completely prevented by inhibition of PI3 kinase or of Akt. This indicates that BDNF modulates NMDA receptor function via PI3 kinase and Akt. Activation of NMDA receptors also leads to phosphorylation and activation of Akt which, in turn, potentiates NMDA receptor activation. The results reported indicate that when Akt activity increases the activation of NMDA receptors by its agonists also increases. Akt may play important roles in the modulation of NMDA receptor responses by other neurotransmitters and modulators and in the adaptation of NMDA receptor function to the physiological environmental conditions.     

NMDA receptor dependent and independent components of veratridine toxicity in cultured cerebellar neurons are prevented by nanomolar concentrations of terfenadine

Summary. Exposure of cultured neurons to nanomolar concentrations of terfenadine prevented the NMDA receptor-mediated early appearance (30 min.) of toxicity signs induced by the voltage sensitive sodium channel activator veratridine. Terfenadine also provided an histamine-insensitive protection against delayed neurotoxicity by veratridine (24 h), occurring independently of NMDA receptor activation, while not protecting from excitotoxicity following direct exposure of neurons to glutamate. Terfenadine reduced tetrodotoxin-sensitive inward currents, and reduced intracellular cGMP formation following veratridine exposure. Our data suggest that nanomolar concentrations of TEF may reduce excitatory aminoacid release following neuronal depolarization via a presynaptic mechanism involving voltage sensitive sodium channels, and therefore may be considered as a prototype for therapeutic drugs in the treatment of diseases that involve excitatory aminoacid neurotransmission. Received August 31, 1999 Accepted September 20, 1999     

Low extracellular zinc increases neuronal oxidant production through nadph oxidase and nitric oxide synthase activation

A decrease in zinc (Zn) levels increases the production of cell oxidants, affects the oxidant defense system and triggers oxidant sensitive signals in neuronal cells. However, the underlying mechanisms are still unclear. This work tested the hypothesis that the increase in neuronal oxidants that occurs when cellular Zn decreases is mediated by the activation of the NMDA receptor. Differentiated PC12 cells were cultured in control, Zn-deficient or Zn-repleted media. The incubation in Zn deficient media led to a rapid increase in cellular calcium levels, which was prevented by a NMDA receptor antagonist (MK-801). Cellular calcium accumulation was associated with NADPH oxidase and nitric oxide synthase (NOS) activation, an increase in cell oxidant levels, and an associated activation of a redox-sensitive signal (AP-1). In cells incubated in the Zn deficient medium, NADPH oxidase activation was prevented by MK-801 and by a protein kinase C inhibitor. The rise in cell oxidants was prevented by inhibitors of NADPH oxidase, of the NOS and by MK-801. A similar pattern of inhibitor action was observed for zinc deficiency-induced AP-1 activation. Results demonstrate that a decrease in extracellular Zn leads to an increase in neuronal oxidants through the activation of the NMDAR that leads to calcium influx and to a calcium-mediated activation of protein kinase C/NADPH oxidase and NOS. Changes in extracellular Zn concentrations can be sensed by neurons, which using reactive oxygen and nitrogen species as second messengers, can regulate signaling involved in neuronal development and function.     

UFP-101 antagonizes the spinal antinociceptive effects of nociceptin/orphanin FQ: behavioral and electrophysiological studies in mice

Nociceptin/orphanin FQ (N/OFQ) modulates various biological functions, including nociception, via selective stimulation of the N/OFQ peptide receptor (NOP). Here we used the NOP selective antagonist UFP-101 to characterize the receptor involved in the spinal antinociceptive effects of N/OFQ evaluated in the mouse tail withdrawal assay and to investigate the mechanism underlying this action by assessing excitatory postsynaptic currents (EPSC) in laminas I and II of the mouse spinal cord dorsal horn with patch-clamp techniques. Intrathecal (i.t.) injection of N/OFQ in the range of 0.1-10 nmol produced a dose dependent antinociceptive effect, which was prevented by UFP-101, but not by naloxone. In contrast the antinociceptive effect of the mu-opioid peptide receptor agonist endomorphin-1 was blocked by naloxone but not by UFP-101. Moreover, N/OFQ and endomorphin-1 induced a significant antinociceptive effect in wild type mice while in mice knockout for the NOP receptor gene only endomorphin-1 was found to be active. In mouse spinal cord slices 1 microM N/OFQ reduced EPSC to 60+/-4% of control values. This inhibitory effect was reversed in a concentration dependent manner by UFP-101 (pA2 value 6.44). The present results demonstrate that N/OFQ-induced spinal antinociception in vivo and inhibition of spinal excitatory transmission in vitro are mediated by receptors of the NOP type.