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PubMed1993

Small reduction of capsaicin-induced neurogenic inflammation in human forearm skin by the glucocorticoid prednicarbate.

Capsaicin applied to human skin provokes a response known as neurogenic inflammation. Neuropeptides (substance P, CGRP), released from afferent C-fiber terminals and histamine, secondarily released from mast cells, are supposed to participate in this reaction. We investigated the contribution of arachidonic acid and metabolic products to neurogenic inflammation, using a potent topically applied glucocorticoid and the corresponding vehicle. Arachidonic acid is liberated from membrane phospholipids by phospholipase A2, an enzyme that can be blocked by glucocorticoids. In 12 healthy volunteers, neurogenic inflammation was induced by capsaicin 1% on both upper forearms after 16 h of topical pretreatment with either prednicarbate or vehicle. Neurogenic inflammation was assessed by laser Doppler flowmetry and by planimetry of flare sizes. Prednicarbate significantly reduced the laser Doppler flow values inside the flare responses, as well as the flare sizes themselves. These results show that to some extent glucocorticoids reduce capsaicin-induced neurogenic inflammation.

Administration, Topical↗
PubMed1994

Mast cells are not essential to inflammation in murine model of colitis.

A simple rat model of chronic intestinal inflammation was adapted to mice in order to ascertain whether mast cells play an essential role in its induction or perpetuation. Colitis was induced in C57BL mice by intrarectal administration of trinitrobenzene sulfonic acid in 50% ethanol. Higher doses of trinitrobenzene sulfonic acid per gram of body weight were required in mice than rats, with a narrower effective dose range (the upper dose limited by unacceptable mortality and the lower by decreased inflammation). Colons of treated mice were macroscopically inflamed, with transmural damage, adhesions to adjacent structures, and ulcerations. Inflammation was scored subjectively and by tissue weight and myeloperoxidase content; each index was increased dose-dependently by trinitrobenzene sulfonic acid doses of 0.3-10 mg. Six milligrams of trinitrobenzene sulfonic acid induced reproducible inflammation for up to four weeks. Trinitrobenzene sulfonic acid could induce inflammation in both mast-cell-deficient W/Wv mice and their normal +/+ littermates in a similar fashion. Thus it is possible to induce chronic colitis in the mouse. Mast cells are not essential participants in this process.

Animals↗
PubMed1990

Effects of vitamin A-deficiency and inflammation on the conducting airway epithelium of Syrian golden hamsters.

The effects of vitamin A-deficiency and inflammation were studied in the conducting airways of Syrian golden hamsters. An important goal of the study was to characterize epithelial changes that occur early in vitamin A-deficiency, that might precede yet predispose to infection, and precipitate inflammatory changes in the lungs. Age-matched vitamin A-replete control and vitamin A-deprived hamsters were killed at 33 days of age (preweight-plateau); at 41 days of age (weight plateau-early weight loss); and at 48-55 days of age (prolonged weight plateau followed by weight loss). A tablet containing bromodeoxyuridine (BrdU) was implanted subcutaneously into each hamster 7 h before it was killed. No changes were seen in the conducting airway epithelium of vitamin A-deprived hamsters in the preweight plateau. However, labelling of secretory cells for BrdU was reduced 6-7 fold in the epithelium lining the lobar bronchus (p less than 0.0002) and the bronchioles (p less than 0.0001), and the proportions of ciliated cells were decreased (p less than 0.0001) at both airway levels in vitamin A-deficient hamsters in the weight plateau-early weight loss stage. Changes in cellular morphology were minimal in the intrapulmonary airway epithelium at this time but a few small focal patches of epidermoid metaplasia were seen in the tracheal epithelium. Small foci of inflammation were closely associated with the airways in the weight plateau, and the inflammation became more widespread when the deficiency was prolonged. The results suggest that the defense of the lungs to infection was impaired initially in the vitamin A-deficient hamsters by a widespread reduction in the numbers of ciliated cells throughout the epithelium of the conducting airways (trachea, bronchi, bronchioles). At the foci of inflammation, labelling of epithelial secretory cells for BrdU was greatly increased at all airway levels. A highly stratified cornifying epidermoid metaplasia developed in the tracheal epithelium, and goblet cell metaplasia developed in the cranial portion of the lobar bronchus, in association with submucosal inflammation. Goblet cell metaplasia appeared to be the only abnormality that was not reversed when vitamin A was restored to the diet.

Age Factors↗
PubMed2004

Modulation of allergic and immune complex-induced lung inflammation by bradykinin receptor antagonists.

OBJECTIVE: The effect of bradykinin (B(1) or B(2)) receptor antagonists was studied in allergic and immune-complex-induced lung inflammation. METHODS: Lungs of BALB/c mice were examined 24 h after induction of lung inflammation, either allergic (ovalbumin-sensitized submitted to two aerosol of antigen, one week apart) or immune-complex induced (intratracheal instillation of IgG antibodies followed by intravenous antigen). The bradykinin B(2) receptor antagonist, HOE-140 or bradykinin B(1) receptor antagonist, R-954 were given intraperitoneally (100 microg/kg), 30 min before induction. RESULTS: In allergic inflammation, pre-treatment with R-954 reduced eosinophil infiltration into the lungs, mucus secretion and the airway hyperreactivity to methacholine. Pre-treatment with HOE-140 increased eosinophil infiltration but did not affect the other parameters. In immune-complex inflammation, HOE-140 increased neutrophil infiltration but not their activation nor the hemorrhagic lesions. R-594 pre-treatment did not change the parameters examined. CONCLUSION: These results show important modulatory effects of bradykinin B(1) and B(2) receptor antagonists in both models of lung inflammation.

Animals↗
PubMed2006

Effects of organic chemicals derived from ambient particulate matter on lung inflammation related to lipopolysaccharide.

The effects of components of ambient particulate matter (PM) on individuals with predisposing respiratory disorders are not well defined. We have previously demonstrated that airway exposure to diesel exhaust particles (DEP) or organic chemicals (OC) extracted from DEP (DEP-OC) enhances lung inflammation related to bacterial endotoxin (lipopolysaccharide, LPS). The present study aimed to examine the effects of airway exposure to OC extracted from urban PM (PM-OC) on lung inflammation related to LPS. ICR mice were divided into four experimental groups that intratracheally received vehicle, LPS (2.5 mg/kg), PM-OC (4 mg/kg), or PM-OC + LPS. Lung inflammation, lung water content, and lung expression of cytokines were evaluated 24 h after intratracheal administration. LPS challenge elicited lung inflammation evidenced by cellular profiles of bronchoalveolar lavage fluid and lung histology, which was further aggravated by the combined challenge with PM-OC. The combination with PM-OC and LPS did not significantly exaggerate LPS-elicited pulmonary edema. LPS instillation induced elevated lung expression of interleukin-1beta, macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant, whereas the combined challenge with PM-OC did not influence these levels. All the results were consistent with our previous reports on DEP-OC. These results suggest that the extracted organic chemicals from PM exacerbate infectious lung inflammation. The mechanisms underlying the enhancing effects are not mediated via the enhanced local expression of proinflammatory cytokines.

Air Pollutants↗
PubMed2005

Bosentan, an endothelin receptor antagonist, reduces leucocyte adhesion and inflammation in a murine model of inflammatory bowel disease.

BACKGROUND AND AIMS: Endothelins, a group of polyfunctional cytokines, induce the adhesion of circulating leucocytes to venous endothelium, an initial step in the pathogenesis of a cellular infiltrate in inflammatory bowel disease (IBD). The effect of bosentan, a non-selective endothelin receptor antagonist, on leucocyte adhesion and inflammation in a murine model of IBD was studied. MATERIALS AND METHODS: Thirty BALB/c mice were divided into three groups of 10 animals: untreated controls, chronic colitis [dextran sodium sulphate (DSS), 3% w/v for 30 days], and treatment with bosentan (30 mg/kg i.p. daily on days 26-30). On day 30, adherent and rolling leucocytes and the average rolling velocity were assessed by intravital microscopy. Clinical and histological activity of inflammation were assessed by the disease activity index and modified Dieleman score, respectively. STATISTICS: Kruskal-Wallis test was used, followed by Dunn's method. A value of p<0.05 was considered significant. RESULTS: Compared to healthy controls, mice treated with DSS showed pronounced clinical and histological inflammation, and a higher number of rolling and adhering leucocytes in colonic submucosal venules. Therapy with bosentan significantly reduced clinical and histological inflammation. Adherent leucocyte levels were markedly lower (1.2+/-0.3 vs 23.7+/-2.8 adherent cells per 0.01 mm2, p<0.05). The number of rolling leucocytes was lower but not significantly different. However, rolling velocity was significantly higher (91.5+/-14.0 vs 19.0+/-1.6 microm/s, p<0.05). CONCLUSIONS: Bosentan reduces the adhesion of leucocytes in colonic submucosal venules and reduces inflammation in this mouse model of IBD. By inhibiting leucocyte adhesion, a crucial step in the recruitment of leucocytes to the inflamed tissue, bosentan is a potent therapeutic drug in this animal model. Further studies are necessary to investigate the role of bosentan as a novel drug in human IBD.

Animals↗
PubMed2003

Effects of a new dexamethasone-delivery system (Surodex) on experimental intraocular inflammation models.

BACKGROUND: To investigate the effects of a new biodegradable dexamethasone drug delivery system, Surodex, in two experimental intraocular inflammation models; endotoxin-induced uveitis (EIU) and experimental autoimmune uveoretinitis (EAU). METHODS: Surodex was inserted into the right anterior chambers (ACs) of rats. In the EIU experiment, protein concentration, cell infiltration, and myeloperoxidase (MPO) activity in the aqueous humor were measured 24 h after injection. Eyes were evaluated histopathologically. In the EAU experiment, firstly, Surodex was administered at various days after immunization. Then, Surodex was administered on day 9 and eyes were evaluated histopathologically. Intraocular cytokine levels (IFN-gamma and IL-4) were investigated. RESULTS: In the EIU experiments, eyes with Surodex exhibited significantly reduced inflammation compared with contralateral controls. Protein concentrations, cell infiltrations, as well as MPO activity were reduced. In the EAU experiments, all rats with Surodex given on days 0 or 7 showed no or significantly reduced inflammation in both eyes. Rats treated on day 12 developed reduced inflammation only in the treated eyes. IFN-gamma levels were significantly lower in the eyes with Surodex, whereas IL-4 was not detectable. CONCLUSIONS: This new, biodegradable corticosteroid drug-delivery system is highly effective in suppressing intraocular inflammation, and should be a useful tool to manage uveitis in humans.

Animals↗
PubMed2006

Successful implantation of intravenously administered stem cells correlates with severity of inflammation in murine myocarditis.

The present study was designed to determine whether cardiac inflammation is important for the successful homing of stem cells to the heart after intravenous injection in a murine myocarditis model. Male Bagg albino/c mice were infected with encephalomyocarditis virus (EMCV) to produce myocarditis. Subgroups of mice received single injections by tail vein of embryonic stem cells (ESCs) transfected with green fluorescent protein (GFP) as a marker at days 3, 14, or 60 after infection; other subgroups without stem cell injections were killed at each of these time points to assess the degree of inflammation present. The surviving mice were killed at day 90 after virus infection and hemodynamics, gross pathology, histology, and inflammatory cytokine production in the hearts were measured. Our results indicate that myocardial inflammation was most severe and cytokine production highest at day 14 after EMCV inoculation, and in particular, was strongly positive for interleukin 6. Mice receiving intravenous ESC injections on day 14 after EMCV inoculation showed the largest number of GFP-positive cells at the time of death and the greatest functional improvement compared to uninfected controls without inflammation. We conclude that factors released from myocardium during inflammation are important for enhancing the homing, migration, and implantation of systemically infused stem cells.

Animals↗
PubMed1987

In vivo production of leukotriene B4 and leukotriene C4 in rabbit colitis. Relationship to inflammation.

Leukotriene B4, a proinflammatory compound, recently has been identified as the major metabolite of arachidonic acid in tissue incubations of human and animal colitis. To determine the relationship of inflammation to the in vivo production of leukotrienes, rabbit colitis was induced by formalin enema followed by intravenous infusion of immune complexes, and serial samples were collected by rectal dialysis. Leukotrienes B4 and C4 were measured by radioimmunoassay after high-pressure liquid chromatography. Prostaglandin E2 was assayed after Sephadex chromatography. Leukotrienes were not detected in control animals. Eicosanoid production progressively increased during development of inflammation and correlated with severity of inflammatory cell infiltration (p less than 0.01). Methylprednisolone decreased prostaglandin E2 but did not significantly reduce leukotrienes or inflammation. These data demonstrate that in vivo production of leukotrienes B4 and C4 correlates with indices of inflammation, consistent with the concept that these eicosanoids contribute to the inflammation of colitis.

Animals↗
PubMed1990

Hepatic inflammation in rats with experimental small intestinal bacterial overgrowth.

Hepatobiliary inflammation and other extraintestinal manifestations accompany certain intestinal disorders, perhaps because of proliferation or enhanced transport of luminal bacteria or their phlogistic cell-wall components. Using jejunal self-filling blind loops to create small bowel bacterial overgrowth, we compared biochemical and histological evidence of hepatic inflammation in 3 rat strains chosen for their variable inflammatory responses to bacterial cell wall polymers. Lewis and Wistar rats developed weight loss, hepatomegaly, and hepatic inflammation 4 and 12 wk, respectively, after creation of SFBL. Plasma aspartate aminotransferase levels in Lewis rats 4 wk (578 +/- 77 U/L) and Wistar rats 12 wk (220 +/- 35 U/L) after self-filling blind loops were significantly greater than in rats with self-emptying blind loops (112 +/- 24 U/L, p less than 0.001; 104 +/- 22, p less than 0.05) or sham-operated Lewis (84 +/- 24, p less than 0.001) or Wistar (78 +/- 10, p less than 0.001) rats. Randomized comparison using a histology grading score showed abnormalities that paralleled aminotransferase values. Lewis and Wistar rats with self-filling blind loops had hepatic injury with bile duct proliferation, fibrosis and acute and chronic periportal and focal parenchymal inflammation. Lewis and Wistar rats with self-emptying blind loops developed occasional mild histologic lesions. 50% of Lewis rats with self-filling blind loops for 4 wk died compared with only 15% in other groups. However, Buffalo rats with self-filling blind loops developed no weight loss, hepatomegaly, or hepatic injury. Anaerobic cultures of blood, peritoneum and liver were negative in all strains. Diet-restricted, sham-operated Wistar rats with weights similar to the Wistar rats with self-filling blind loops did not develop histologic abnormalities or elevated aminotransferase levels (76 +/- 31 U/L). These results show that experimental small bowel bacterial overgrowth causes significant hepatic inflammation leading to fibrosis in susceptible rat strains. Caloric deprivation and hepatic bacterial invasion are not etiologically responsible. We suggest that bacterial cell wall polymers or other bacterial toxins from the blind loop cause hepatic lesions in genetically susceptible hosts.

Animals↗
PubMed1995

Spontaneous intestinal inflammation and nitric oxide metabolism in HLA-B27 transgenic rats.

BACKGROUND & AIMS: It has been reported that transgenic rats expressing the HLA-B27 and the beta 2- microglobulin genes develop spontaneous gastrointestinal (GI) inflammation; however, no systematic or quantitative evaluation of this GI inflammation has been reported. Therefore, the objective of this study was to characterize quantitatively the GI injury and inflammation observed in commercially available HLA-B27 transgenic rats. METHODS: HLA-B27 rats and Fisher 344 male controls were used for these studies. Gastric, ileal, and colonic blood-to-lumen clearances of 51Cr-ethylenediaminetetraacetic acid, tissue myeloperoxidase activities, and wet/dry ratios of the various tissues as well as plasma nitrate and nitrite levels were quantified for each control and transgenic animal. RESULTS: Spontaneous ileitis and colitis developed in 5 of 10 HLA-B27 transgenic rats beginning at approximately 17 weeks of age and persisting for an additional 13 weeks. Increases in mucosal permeability and myeloperoxidase activities as well as histological analysis showed intestinal injury and chronic inflammation. Plasma levels of nitrate and nitrite, the stable decomposition products of nitric oxide, were found to be significantly enhanced (fourfold) only in those rats that developed the intestinal inflammation. CONCLUSIONS: The chronic ileitis and colitis observed in HLA-B27 transgenic rats seems to be associated with enhanced NO metabolism.

Animals↗
PubMed1993

Blood-brain barrier permeability and the brain extracellular space in acute cerebral inflammation.

The diffusion properties of the brain cortical extracellular space have never been examined in models of inflammation, even though inflammation can cause increased blood-brain barrier permeability. Uptake of intravascular 125I-labelled albumin and the diffusion of the tetramethylammonium ion within the brain extracellular space was measured in an experimental brain abscess to determine the effect of acute inflammation upon blood-brain barrier permeability and diffusion properties of the cortical extracellular space. The blood-brain transfer constant for albumin was increased in the abscess region, indicating that an increase in blood-brain barrier permeability occurred in animals inoculated with a weakly pathogenic strain of Staphylococcus aureus. The volume fraction of the extracellular space, as measured by the diffusion of tetramethylammonium ion, ranged from 0.19 to 0.23 in bacteria inoculated subjects and from 0.21 to 0.22 in controls. The tortuosity of the extracellular space ranged from 1.40 to 1.42 in bacteria inoculated subjects and was 1.39 in controls. These results showed that the volume fraction and tortuosity of the cortical extracellular space were not affected by inflammation even though vascular permeability was increased. This result was supported by the finding that brain water content, measured in the same animals, was increased to a non-significant extent in the bacteria inoculated subjects. These findings lead to the conclusion that acute inflammation induced by a weak pathogen can cause increased blood-brain barrier permeability without a significant change in the diffusion properties of the brain cortical space.

Animals↗
PubMed1992

Glucocorticoid inhibition of inflammation-induced metallothionein synthesis in mouse liver.

The effects of glucocorticoid treatment on the induction of hepatic metallothionein (MT) during inflammation initiated by turpentine oil (TUR) or endotoxin (LPS) were studied in mice. The administration of TUR increased concentrations of hepatic MT as well as that of plasma fibrinogen. Although hepatic MT was modestly induced by dexamethasone (DEX) alone, pretreatment with DEX (12.5 to 100 mg/kg, sc) inhibited the increases both in hepatic MT and in plasma fibrinogen from a subsequent dose of TUR 6 hr after DEX administration. The concentration of hepatic MT in the DEX-pretreated (25 mg/kg) group was higher than that in the nonpretreated group 4 hr after administration of TUR, but after 24 hr, the MT concentration in the DEX-pretreated group was inhibited to 20% of that in the nonpretreated group. These inhibitory effects were also observed by prednisolone (PRE) but not by salicylic acid. The inhibitory effect of DEX on the induction of MT synthesis during inflammation was observed after administration of the exudate obtained from inflamed tissue. When inflammation was initiated by an injection of LPS as well as TUR, pretreatment of either DEX or PRE inhibited the increase of hepatic MT. Pretreatment of DEX did not affect the induction of hepatic MT synthesis by cadmium. In contrast to inflammation initiated by TUR or LPS, pretreatment of DEX caused an additive increase of hepatic MT concentration after administration of zinc. These results suggest that glucocorticoids, despite being direct inducers of MT, inhibit the induction of MT synthesis during inflammation by the suppression of cytokine production.

Animals↗
PubMed1986

Tocainide suppression of immune-complex-mediated dermal inflammation: comparison with prostaglandin E1.

Local anesthetic agents have been shown to alter a variety of polymorphonuclear leukocyte (PMN) functions and may be useful as anti-inflammatory agents. We compared the anti-inflammatory effects of therapeutic doses of the recently released local anesthetic-antiarrythmic drug tocainide to pharmacologic doses of prostaglandin E1 (PGE1) on immune-complex-mediated dermal inflammation in female Sprague-Dawley rats. Intense dermal inflammation was produced using a classic reverse passive Arthus reaction, and the inhibition of PMN accumulation in the subdermis was quantitated in biopsy samples taken 2.5 hr after the reaction was initiated and the drug was given. Using a light microscope with a counting grid, biopsy sections were randomly sampled in a blinded fashion and an inflammation index equal to the ratio of PMNs to fibroblasts was determined for each animal. The mean inflammation index in 10 animals given 25 mg of tocainide (mean serum level = 14.6 micrograms/ml) was 9.3 +/- 1.2 (+/- SEM), which was significantly less than the index of 17.7 +/- 2.5 in 10 control animals (P less than 0.025). Similarly, the five animals that received either 500 or 250 micrograms of PGE1 had a significantly reduced index, with the effect of 250 micrograms PGE1 comparable to the effect of the tocainide. These findings suggest that therapeutic levels of tocainide reduce the accumulation of PMNs in immune-complex-mediated dermal inflammation; thus, local anesthetic agents may be useful in the treatment of certain inflammatory disorders.

Alprostadil↗
PubMed1988

Effects of 16,16-dimethyl prostaglandin E2 and indomethacin on leukotriene B4 and inflammation in rabbit colitis.

The role of increased prostaglandin production and the effects of exogenous prostaglandins on inflammation of colitis are not established. We administered intramuscular 16,16-dimethyl prostaglandin E2 (DiM-PGE2) and indomethacin to rabbits with formalin immune-complex colitis and measured leukotriene B4 (LTB4), prostaglandin E2 (PGE2) and severity of inflammation. DiM-PGE2 (100 micrograms/kg/BID) reduced LTB4 production (from 401 +/- 108 to 216 +/- 58 pg/ml) and infiltration of neutrophils, mucosal necrosis, inflammatory exudate and edema (all P less than 0.05). Other studies determined that parenteral DiM-PGE2 did not reduce the initial chemical damage induced by formalin, suggesting that cytoprotection of chemical insult was not the mechanism of suppressed inflammation in the immune colitis model. Indomethacin (10 mg/kg/d) reduced endogenous PGE2 by 80%, but did not reduce leukotriene production or inflammation. Exogenous prostaglandins cause a dose-dependent suppression of inflammation in experimental colitis, by a mechanism other than cytoprotection of chemical-induced mucosal injury.

Animals↗
PubMed1990

Common bile ligation in the rabbit: an appropriate model for investigating the relationship of endogenous gallbladder prostanoid synthesis with evolving acute inflammation.

Gallbladder prostanoid (PG) synthesis and histologic inflammatory changes were compared after 6, 24, and 72 hours of bile duct ligation (BDL) or cystic duct ligation (CDL) in the male rabbit. At each time interval the gallbladder was scored for degree of acute inflammation, examined by radiochromatography for endogenous PG synthesis and analyzed by ANOVA. BDL induced progressive increases in acute inflammation whereas prostanoid synthesis significantly increased only after the 6 and 72 hour groups. Indomethacin treatment inhibited PG synthesis in all BDL groups but only decreased the inflammation score in the 6 and 24 hour BDL groups. CDL did not induce progressive gallbladder inflammatory changes or prostanoid synthesis. These data show that prostanoids are intimately involved with the development of early acute gallbladder inflammation following BDL. Inhibition of PG synthesis could attenuate or retard the progression of early acute gallbladder inflammation if started prior to development of established disease.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

The contribution of epinephrine to experimentally induced urethral inflammation in the rat.

We have studied the effect of the adrenal medulla and epinephrine on experimentally induced urethral inflammation in the rat. Urethral inflammation was induced by inserting latex strips into the urethra. The effects of different experimental procedures were assessed by using a 4-graded inflammation scale based on histological findings. Adrenal medullectomy significantly reduced experimentally induced urethral inflammation. This effect was reversed if the rats were treated repeatedly with epinephrine or salbutamol. On the other hand high doses of epinephrine reduced the experimentally induced urethral inflammation.

Adrenal Medulla↗
PubMed1992

The effects of a non-competitive NMDA receptor antagonist, MK-801, on behavioral hyperalgesia and dorsal horn neuronal activity in rats with unilateral inflammation.

The involvement of NMDA receptors in rats with peripheral inflammation and hyperalgesia was evaluated by administration of the non-competitive NMDA receptor antagonist, MK-801. Inflammation and hyperalgesia was induced by intradermal injection of complete Freund's adjuvant (CFA) or carrageenan into the left hind paw. The latency of paw withdrawal from a thermal stimulus was used as a measure of hyperalgesia in awake rats. MK-801 (1.6 mg/kg, i.p., or 31.5 micrograms, intrathecal) significantly attenuated thermal hyperalgesia and reduced its duration in comparison to saline-injected rats (P less than 0.05). The receptive field size of nociceptive-specific and wide-dynamic-range neurons in the superficial and deep spinal dorsal horn recorded 24 h after injection of CFA was significantly reduced to 73 +/- 6% (P less than 0.05, n = 8) and 74 +/- 4% (P less than 0.05, n = 8) of control values, respectively, by a cumulative dose of 3 mg/kg of MK-801 (i.v.). MK-801 (2 mg/kg) prevented the expansion of the receptive fields of dorsal horn neurons recorded 5 +/- 0.4 h (n = 5) after intradermal injection of CFA as compared to saline-injected rats (P less than 0.05). MK-801 had no significant effect on receptive field size of dorsal horn neurons in rats without CFA-induced inflammation but blocked a transient expansion of the receptive fields induced by 1 Hz, C-fiber intensity electrical stimulation of the sciatic nerve. The background activity and noxious heat-evoked response of dorsal horn neurons in rats with CFA-induced inflammation were primarily inhibited and noxious pinch-evoked activity was both facilitated and inhibited by the administration of MK-801. These results support the hypothesis that NMDA receptors are involved in the dorsal horn neuronal plasticity and behavioral hyperalgesia that follows peripheral tissue inflammation.

Animals↗