Effect of cholecystokinin blockade on the recovery of alterations induced by acute pancreatitis in glycoconjugates of rat zymogen granules

Lectin-binding studies have been performed on rat zymogen granules to investigate alterations in the carbohydrate membrane composition that occur in acute pancreatitis induced by caerulein. The influence of treatment with hydrocortisone for seven days before inducing pancreatitis was also studied. Lectin labeling on zymogen granules was also analyzed seven days after inducing pancreatitis in rats that had previously received a hydrocortisone treatment. During this period L 364,718 (0.1 mg/kg)—specific cholecystokinin (CCK) receptor antagonist—was administered daily to some of the rats, and no treatment was applied to others. Using fluorescein-labelled T. purpureus (TP)lectin, a significant decrease in the amount of L-fucose in the granule membrane was observed in rats with caerulein-induced pancreatitis. This effect was directly caused by the pancreatitis and was not influenced by previous hydrocortisone treatment. Seven days later, the density of TP receptors in the granule membrane was similar to the controls both in L-364,718-treated and untreated rats. Therefore, we suggest that endogenous CCK is not an essential factor in the recovery of L-fucose containing glycoconjugates the granule membrane after pancreatitis. Acute pancreatitis did not alter the expression of wheat germ agglutinin (WGA) receptors in the zymogen granule membrane. WGA specifically binds N-acetyl glucosamine and sialic acids. L 364,718 administered for seven days after inducing pancreatitis significantly reduced WGA binding, untreated rats showed a normal zymogen granule membrane. Therefore, the blockade of CCK-induced alterations in membrane glycoconjugates enriched in N-acetyl glucosamine and sialic acid of newly formed granules after pancreatitis, a finding that could explain the delay in the regression of the disease.     

Anti‐inflammatory effects of melatonin in a rat model of caerulein‐induced acute pancreatitis

The purpose of our study was to evaluate the protective effect of melatonin in a rat model of caerulein‐induced acute pancreatitis. For the induction of experimental acute pancreatitis, four subcutaneous injections of caerulein (20 µg kg^–1 body weight) were given to Wistar rats at 2‐h intervals. Melatonin was injected intraperitoneally (25 mg kg^–1 body weight) 30 min before each caerulein injection. After 12 h, rats were sacrificed by decapitation. Blood and pancreas samples were collected and processed for serological and histopathological studies, respectively. Lipase, α‐amylase, corticosterone, total antioxidant power and cytokines interleukin (IL)‐1β, IL‐4 and tumour necrosis factor (TNF)‐α were determined using commercial kits. ANOVA and Tukey tests (P < 0.05) were performed for the statistical analysis of the results. Results showed that the administration of melatonin reduced histological damage induced by caerulein treatment as well as the hyperamylasemia and hyperlipidemia. Corticosterone and antioxidant total power were also reverted to basal activities. Furthermore, melatonin pre‐treatment reduced pro‐inflammatory cytokines IL‐1β and TNF‐α and increased the serum levels of anti‐inflammatory cytokine IL‐4. In conclusion, the findings suggest that the protective effect of melatonin in caerulein‐induced acute pancreatitis is mediated by the anti‐inflammatory ability of this indolamine. Thus, melatonin may have a protective effect against acute pancreatitis. Copyright © 2013 John Wiley & Sons, Ltd.     

Central role of neutrophil in the pathogenesis of severe acute pancreatitis

Severe acute pancreatitis (SAP) is an acute abdominal disease with the strong systemic inflammatory response, and rapidly progresses from a local pancreatic damage into multiple organ dysfunction. For many decades, the contributions of neutrophils to the pathology of SAP were traditionally thought to be the chemokine and cytokine cascades that accompany inflammation. In this review, we focus mainly on those recently recognized aspects of neutrophils in SAP processes. First, emerging evidence suggests that therapeutic interventions targeting neutrophils significantly lower tissue damage and protect against the occurrence of pancreatitis. Second, trypsin activation promotes the initial neutrophils recruitment into local pancreas, and subsequently neutrophils infiltration in turn triggers trypsin production. Finally, neutrophils have the unique ability to release neutrophil extracellular traps even in the absence of pathogens.     

重症急性胰腺炎合并腹腔感染的感染特点和相关因素分析

目的 探讨重症急性胰腺炎（SAP）合并腹腔感染的感染特点及其相关因素分析。方法 回顾性分析2008年1月至2015年6月我院收治的125例SAP患者的临床资料,分析腹腔感染细菌菌谱的特点及影响腹腔感染发生的危险因素。结果 125例患者中48例（38.40%）合并腹腔感染,死亡12例（9.60%）。共培养出病原菌92株,其中革兰阴性菌61株（66.30%）,革兰阳性菌25株（27.17%）和真菌6株（6.52%）。单因素分析显示病因、APACHEⅡ评分、合并多器官功能障碍综合征（MODS）、外科干预及全肠外营养时间与SAP发生腹腔感染有关（P0.05）。多因素分析结果显示,APACHE Ⅱ评分≥11、合并MODS、全肠外营养时间≥1周是SAP发生腹腔感染的独立危险因素（P<0.05）。结论 SAP合并腹腔感染多为多重感染,以革兰阴性菌感染为主。APACHE Ⅱ评分≥11、合并MODS、全肠外营养时间≥1周的SAP患者,易并发腹腔感染。     

益生菌联合早期肠内营养治疗重症急性胰腺炎临床疗效的Meta分析

目的 系统性评价益生菌联合早期肠内营养对重症急性胰腺炎(sever acute pancreatitis,SAPP)的临床疗效.方法 计算机检索中国知网、万方数据库、维普期刊数据库、PubMed、Embase和The Co-chrane Library,收集关于益生菌联合早期肠内营养治疗SAP的临床随机对照试验(ran...     

胰腺p-STAT3在急性胰腺炎危重演变中的表达变化

目的：检测信号转导与转录激活因子3（STAT3）在不同程度胰腺炎模型小鼠胰腺组织中表达的变化,探讨其在急性胰腺炎危重演变中的作用。方法：48只健康雄性balb/c小鼠随机分为3组（n=16）：对照组（Con）、轻症急性胰腺炎（MAP）组、重症急性胰腺炎（SAP）组。Con组腹腔注射0.9% NaCl;MAP组腹腔注射雨蛙素;SAP组腹腔注射雨蛙素联合脂多糖;分别于造模后2 h、6 h检测血清淀粉酶的活性;分离胰腺、称重,计算胰腺湿重比;检测肺组织髓过氧化物酶（MPO）活性,评估炎细胞浸润肺组织的程度;HE染色切片,光镜下观察胰腺、肺组织病理学改变; Western blot法检测磷酸化STAT3（p-STAT3）的变化。结果：与Con组比较, MAP组和SAP组在各时间点血清淀粉酶活性和胰腺组织湿重比均升高（P<0.05）;肺组织MPO活性显著升高（P<0.05）,且SAP组肺MPO含量明显高于MAP组（P<0.01）。MAP组和SAP组,在造模后2 h,胰腺和肺均可见不同程度的病理学改变; SAP组在造模后2 h胰腺p-STAT3的表达最高,6 h表达有所减弱;MAP组各时间点仅有微量表达;Con组在各时间点为阴性表达。结论：p-STAT3在轻症急性胰腺炎和重症急性胰腺炎模型小鼠胰腺中的表达差异明显,说明重症急性胰腺炎的重症化与STAT3的活化关系密切;抑制STAT3活化将成为阻止急性胰腺炎重症化的靶点之一。     

早期肠内营养联合微生态制剂对重症急性胰腺炎患者的临床疗效及其对免疫功能的影响

目的 分析早期肠内营养联合微生态制剂对重症急性胰腺炎患者的临床疗效及其免疫功能的影响。 方法 选择我院2017年6月至2020年1月间收治的80例符合标准的重症急性胰腺炎患者为研究对象并随机分为观察组和对照组,每组40例。对照组患者给予早期肠内营养干预。观察组患者采用早期肠内营养加微生态制剂治疗。评估患者疗效,同时评估治疗前、治疗7 d及治疗14 d时患者腹内压、胃肠功能、免疫球蛋白、炎症因子、淀粉酶、血清脂肪酶、血清乳酸脱氢酶及T细胞亚群水平。 结果 观察组患者临床总有效率高于对照组(97.50% vs 80.00%,P+、CD4+水平和CD4+/CD8+比值显著高于对照组,而CD8+水平低于对照组(均P结论 早期肠内营养联合微生态制剂可显著提高重症急性胰腺炎患者的临床疗效,并改善患者免疫功能。     

肠道微生物在重症急性胰腺炎进展中的作用及其潜在的治疗意义

重症急性胰腺炎是临床常见的消化系统急危重症,起病急、变化快、并发症多、病死率高,但尚无特效疗法,是目前医学界面临的一大难题.近年来,肠道微生物因其在人类健康和疾病中的重要作用而受到越来越多的关注.研究表明,重症急性胰腺炎早期即存在肠道微生物失调,而由胰腺炎引起的菌群失调和菌群移位导致的肠源性感染是影响重症急性胰腺炎严重...     

Necro-inflammatory response of pancreatic acinar cells in the pathogenesis of acute alcoholic pancreatitis

The role of pancreatic acinar cells in initiating necro-inflammatory responses during the early onset of alcoholic acute pancreatitis (AP) has not been fully evaluated. We investigated the ability of acinar cells to generate pro- and anti-inflammatory mediators, including inflammasome-associated IL-18/caspase-1, and evaluated acinar cell necrosis in an animal model of AP and human samples. Rats were fed either an ethanol-containing or control diet for 14 weeks and killed 3 or 24 h after a single lipopolysaccharide (LPS) injection. Inflammasome components and necro-inflammation were evaluated in acinar cells by immunofluorescence (IF), histology, and biochemical approaches. Alcohol exposure enhanced acinar cell-specific production of TNFα, IL-6, MCP-1 and IL-10, as early as 3 h after LPS, whereas IL-18 and caspase-1 were evident 24 h later. Alcohol enhanced LPS-induced TNFα expression, whereas blockade of LPS signaling diminished TNFα production in vitro, indicating that the response of pancreatic acinar cells to LPS is similar to that of immune cells. Similar results were observed from acinar cells in samples from patients with acute/recurrent pancreatitis. Although morphologic examination of sub-clinical AP showed no visible signs of necrosis, early loss of pancreatic HMGB1 and increased systemic levels of HMGB1 and LDH were observed, indicating that this strong systemic inflammatory response is associated with little pancreatic necrosis. These results suggest that TLR-4-positive acinar cells respond to LPS by activating the inflammasome and producing pro- and anti-inflammatory mediators during the development of mild, sub-clinical AP, and that these effects are exacerbated by alcohol injury.     

柴芩承气汤对重症急性胰腺炎并发肝损伤大鼠的治疗作用及其机制

目的：研究柴芩承气汤（CQCQD）对重症急性胰腺炎（SAP）并发肝损伤大鼠的治疗作用及其机制。方法：72只SD大鼠随机分为3组（n=24）：假手术（sham）组,重症急性胰腺炎模型（SAP）组和柴芩承气汤治疗（CQCQD）组。去氧胆酸钠胰胆管逆行注射建立SAP大鼠模型,CQCQD组给予柴芩承气汤治疗,于造模后1 h、5 h、10 h观察各组不同时间点的胰腺、肝脏组织病理学变化,检测血清中淀粉酶（AMS）、丙氨酸氨基转移酶（ALT）、天冬氨酸氨基转移酶（AST）活性、白介素-6（IL-6）水平及胰腺、肝脏组织单核细胞趋化蛋白-1（MCP-1）和IL-6 mRNA的表达情况。结果：与sham组比较,SAP组血清AMS、ALT、AST活性及IL-6水平明显升高,胰腺、肝脏组织MCP-1及IL-6 mRNA表达升高（P<0.05）;与SAP组比较,CQCQD组血清AMS、ALT、AST活性及IL-6水平明显降低;胰腺和肝脏组织病理损伤减轻,胰腺、肝脏组织MCP-1及IL-6 mRNA表达明显减弱（P<0.05）。结论：MCP-1参与了SAP并发肝损伤的进展;柴芩承气汤能显著抑制胰腺、肝脏组织MCP-1的表达,减轻SAP时胰腺、肝脏组织病理损伤,对SAP并发肝损伤起到治疗作用。     

Role of CARD9 in inflammatory signal pathway of peritoneal macrophages in severe acute pancreatitis

Previous studies revealed that caspase recruitment domain protein 9 (CARD9) was involved in severe acute pancreatitis (SAP) inflammation and that interfering with its expression in vivo could inhibit inflammation. However, the specific mechanism is unknown. This study aimed to discover the related signal pathways of CARD9 in macrophages. SiRNA interference technology was used in vivo and in vitro to detect CARD9‐related signal pathways in peritoneal macrophages. Furthermore, Toll‐like receptor 4 (TLR4) and membrane‐associated C‐type lectin‐1 (Dectin‐1) pathways in macrophages were activated specially to looking for the upstream signal path of CARD9. Results showed up‐regulation of CARD9 expression in peritoneal macrophages of SAP rats (P < .05). CARD9 siRNA alleviated inflammatory cytokines, and inhibited the phosphorylation of NF‐κB and p38MAPK in peritoneal macrophages in vivo or in vitro. Meanwhile, CARD9 siRNA reduced the concentration of CARD9 and Bcl10 in peritoneal macrophages, and TLR4 and Dectin‐1 took part in CARD9 signal pathways in macrophages. In conclusion, there is an inflammation signal pathway comprised of TLR4/Dectin‐1‐CARD9‐NF‐κB/p38MAPK activated in macrophages in SAP. Blockade of CARD9 expression in macrophages can effectively alleviate SAP inflammation.     

心肌梗死大鼠钙敏感受体表达与心肌细胞凋亡的变化

目的:观察大鼠急性心肌梗死后不同时间心肌钙敏感受体(CaSR)的表达和心肌细胞凋亡的变化情况。方法:健康Wistar大鼠随机分为假手术组(Sham)和心肌梗死(AMI)组,通过结扎左侧冠状动脉前降支的方法,建立大鼠心肌梗死模型,分别在手术后1、2、4周(每组成功存活n=5)检测心脏形态学和血流动力学的改变,检测心肌组织中CaSRmRNA和蛋白的表达,以及Bax、Bcl-2、caspase-3和caspase-9蛋白的表达,检测血清中乳酸脱氢酶(LDH)、肌酸激酶(CK)活性和肌钙蛋白(cTnT)水平,观察心肌细胞凋亡情况。结果:和Sham组相比,随着心肌梗死的发展,AMI组大鼠心肌组织CaSR的mRNA和蛋白的表达、细胞凋亡指数均明显增加(P<0.05),心肌细胞超微结构损伤严重;左心室收缩压(LVSP)、左心室内压最大上升速率(+dp/dtmax)(mmHg/s)和最大下降速率(-dp/dtmax)(mmHg/s)减少,左心室舒张末期压(LVEDP)明显增大(P<0.05);AMI组血清cTnT水平、CK和LDH活性均升高(P<0.05),随着心肌梗死的发展,cTnT水平和CK活性逐渐降低,LDH变化不明显。心肌组织中促凋亡相关蛋白Bax、caspase-3、caspase-9表达增多,抑制凋亡的相关蛋白(或因子)Bcl-2表达减少(P<0.05)。结论:随着AMI的发展,AMI组大鼠心肌组织中CaSR的mRNA和蛋白的表达增多,细胞凋亡数增加,表明CaSR参与了心肌梗死的发展,其机制可能与促进细胞凋亡有关。     

骨髓间充质干细胞对重症急性胰腺炎胰腺组织修复的促进作用研究

目的观察骨髓间充质干细胞（BMSCs）抑制坏死性凋亡促进修复重症急性胰腺炎（SAP）的可能机理。 方法（1）分离、培养和鉴定大鼠BMSCs;（2）构建牛磺胆酸钠（NaT）诱导的SAP大鼠模型,并分成正常组（NC）、假手术组（Sham）、SAP模型组（SAP）、PBS治疗组（PBS）、BMSCs治疗组和Necrostain-1 （Nec-1）治疗组,并检测胰腺病理评分和血淀粉酶水平;（3）运用Western Blot和qRT-PCR方法检测各组受损胰腺组织内RIPK1、RIPK3、Caspase-8、MLKL蛋白及mRNA表达,各组均数间比较采用单因素方差分析,两两比较采用LSD-t检验。 结果BMSCs可以被诱导分化成骨、软骨、脂肪,并高表达CD44 （99.82﹪）、CD73 （99.87﹪）、CD90 （99.99﹪）、CD105 （99.78﹪）,低表达CD11b （0.65﹪）、CD19 （0.85﹪）、CD34 （0.70﹪）和CD45 （1.20﹪）。SAP组胰腺病理评分（12.90±1.79）及血淀粉酶水平（1052.41±183.12） mU/ ml均高于NC组[评分：0.40±0.52,淀粉酶水平：（236.62±33.21） mU/ ml]和Sham组[评分：0.50±0.53,淀粉酶水平：（242.31±27.94） mU/ ml]（F = 200.275,F = 143.245,P均< 0.001）,且SAP组受损胰腺组织内RIPK1、RIPK3、MLKL表达升高、Caspase-8表达降低（F = 179.905,P < 0.001）;BMSCs组和Nec-1治疗组胰腺病理评分及血淀粉酶水平均低于PBS治疗组[评分：7.20±1.23、7.00±1.05比12.60±1.65,F = 200.275,P < 0.001;淀粉酶水平：（452.21±101.68）mU/ml、（570.18±148.47） mU/ml比（972.77±204.29） mU/ml,F = 143.245,P < 0.001],同时受损胰腺组织内RIPK1、RIPK3、MLKL表达下调、Caspase-8表达升高（F = 179.905,P < 0.001）。 结论BMSCs可能通过抑制坏死性凋亡通路活化来修复SAP。     

The role of Card9 overexpression in peripheral blood mononuclear cells from patients with aseptic acute pancreatitis

Activated mononuclear cells are an early event in the course of severe acute pancreatitis (SAP). To date, the molecular mechanism triggering peripheral blood mononuclear cells (PBMCs) is poorly understood. The aim of this paper was to determine the potential role of Card9 in SAP. We collected data from 72 subjects between January 2013 and June 2014. Subsequently, PBMCs were isolated on day 1, 3 and 5 of pancreatitis. Immunofluorescence staining, quantitative real‐time PCR, Western blotting, immunoprecipitation and ELISA were used to determine the role of Card9 in SAP. Microbial culture showed that SAP patients at the early period did not develop any bacteria and fungi infection. Card9 expression in SAP patients was higher than that in mild acute pancreatitis and volunteer healthy controls, up to the peak on day 1. The monocyte‐derived cytokines interleukin (IL)‐17, IL‐1β, IL‐6 and tumour necrosis factor‐α mediated by the induction of Card9 markedly increased in SAP patients compared with the control group. Furthermore, the inducible formation of Card9‐Bcl10 complex was found in PBMCs, which may be involved in nuclear factor kappa B (NF‐κB) and p38 activation in SAP. Receiver operating characteristic curve indicated that Card9 levels had a high sensitivity of 87.5% and specificity of 67.7%, showing the close correlation with SAP patients. Card9 overexpression was firstly found in aseptic SAP, which may be played an important role in NF‐κB and p38 activation in PBMCs. It also provided the new insights into therapeutic interventions by targeting monocytes activation in SAP patients.     

Effect of microRNA-27a-5p on apoptosis and inflammatory response of pancreatic acinar cells in acute pancreatitis by targeting PTEN

To investigate the apoptosis and inflammatory response of microRNA-27a-5p (miR-27a-5p) in pancreatic acinar cells of acute pancreatitis (AP) and its related mechanisms. Rat pancreatic acinar cell line AR42J was treated with caerulein (10nmol/L) to construct an acute pancreatitis cell model. Quantitative real-time polymerase chain reaction was performed to measure the expression of miR-27a-5p; The miR-27a-5p mimic was transfected into cell, and the apoptosis rate of the cells was detected by flow cytometry; The levels of TNF-α, IL-1, and IL-6 in the culture supernatant were determined by enzyme-linked immunosorbent assay; TargetScans database predicted and dual luciferase reporter gene assay verified the relationship between miR-27a-5p and the phosphatase and tensin homolog deleted on chromosome 10 (PTEN); The recovery experiment explored the apoptosis and the effects of inflammatory responses. The expression of miR-27a-5p decreased gradually (P < 0.05) and the expression of PTEN increased gradually (P < 0.05) with the prolongation of acting time. Upregulation of miR-27a-5p significantly promoted cell apoptosis (P < 0.05) and inhibited inflammatory response (P < 0.05); The TargetScans database predicted that the 3'UTR of PTEN contains a base complementary to the miR-27a-5p seed region. Cotransfection of wild-type vector (PTEN-WT) with miR-27a-5p mimic or miR-27a-5p inhibitor significantly affected the relative activity of luciferase (P < 0.05), and no significant impact was observed in mutant PTEN-MUT. Compared with miR-27a-5p + pcDNA group, transfection of miR-27a-5p mimic and pcDNA-PTEN significantly increased the expression of PTEN (P < 0.05), decreased the apoptotic rate (P < 0.05), and increased the inflammatory response (P < 0.05). miR-27a-5p induced apoptosis and inhibited the inflammatory response of pancreatic acinar cells in AP by targeting PTEN.     

Changes in the expression of LIMP-2 during cerulein-induced pancreatitis in rats: Effect of inhibition of leukocyte infiltration,cAMP and MAPKs early on in its development

Lysosomal integral membrane protein-2 (LIMP-2) is an important protein in lysosomal biogenesis and function and also plays a role in the tissue inflammatory response. It is known that lysosomes play a central role in acute pancreatitis, with inflammatory cell infiltration triggering the disease early on. In this study we report increases in pancreatic LIMP-2 protein and mRNA levels as early events that occur during the development of cerulein (Cer)-induced acute pancreatitis (AP) in rats. GdCl₃, a macrophage inhibitor, but not FK506, a T lymphocyte inhibitor, was able to reverse the increase in LIMP-2 expression after Cer treatment, although such reversion was abolished if the animals were depleted of neutrophils due to a vinblastine sulfate pre-treatment. Immunostaining revealed that the cellular source of LIMP-2 was mainly acinar cells. Additionally, pre-treatments with the MAPKs inhibitors SP600125 and PD98059, inhibitors of JNK and ERK½ activation, respectively, but not of rolipram, a type IV phosphodiesterase inhibitor, suppressed the increase in the expression of LIMP-2 after Cer administration. Together, these results indicate that neutrophils are able to drive a macrophage activation that would regulate the increase in LIMP-2 expression during the early phase of Cer-induced AP, with the stress kinases JNK and ERK½ also playing a coordinated role in the increase of LIMP-2 expression due to Cer.     

Protective effects of the notoginsenoside R1 on acute lung injury by regulating the miR-128-2-5p/Tollip signaling pathway in rats with severe acute pancreatitis

Notoginsenoside R1 (NG-R1), the extract and the main ingredient of Panax notoginseng, has anti-inflammatory effects and can be used in treating acute lung injury (ALI). In this study, we explored the pulmonary protective effect and the underlying mechanism of the NG-R1 on rats with ALI induced by severe acute pancreatitis (SAP). MiR-128-2-5p, ERK1, Tollip, HMGB1, TLR4, IκB, and NF-κB mRNA expression levels were measured using real-time qPCR, and TLR4, Tollip, HMGB1, IRAK1, MyD88, ERK1, NF-κB65, and P-IκB-α protein expression levels using Western blot. The NF-κB and the TLR4 activities were determined using immunohistochemistry, and TNF-α, IL-6, IL-1β, and ICAM-1 levels in the bronchoalveolar lavage fluid (BALF) using ELISA. Lung histopathological changes were observed in each group. NG-R1 treatment reduced miR-128-2-5p expression in the lung tissue, increased Tollip expression, inhibited HMGB1, TLR4, TRAF6, IRAK1, MyD88, NF-κB65, and p-IκB-α expression levels, suppressed NF-κB65 and the TLR4 expression levels, reduced MPO activity, reduced TNF-α, IL-1β, IL-6, and ICAM-1 levels in BALF, and alleviated SAP-induced ALI. NG-R1 can attenuate SAP-induced ALI. The mechanism of action may be due to a decreased expression of miR-128-2-5p, increased activity of the Tollip signaling pathway, decreased activity of HMGB1/TLR4 and ERK1 signaling pathways, and decreased inflammatory response to SAP-induced ALI. Tollip was the regulatory target of miR-128-2-5p.     

The effects of NMDA receptor antagonists on acute morphine antinociception in mice

Summary.  Antagonists of the N-methyl-d-aspartate (NMDA) receptor complex inhibit the development of tolerance to antinociceptive effects of morphine and upon acute administration, influence morphine antinociceptive activity. The analysis of numerous studies investigating acute interaction between NMDA receptor antagonists and morphine in mice indicate a variety of procedural differences and reveal that these compounds may potentiate, attenuate and produce no effect on morphine antinociception. The conditions responsible for such conflicting experimental outcome of acute interaction remain unclear. It appears that the effects of NMDA receptor antagonists on morphine tolerance are not causally related to their acute effects on morphine antinociception. Received July 6, 2001 Accepted August 6, 2001 Published online August 9, 2002