Antinociceptive and anti-inflammatory effect of Poincianella pyramidalis (Tul.) L.P. Queiroz.

ETHNOPHARMACOLOGY RELEVANCE: Poncianella pyramidalis (Leguminosae) is a Caatinga plant used in folk medicine because of its pharmacological properties, which include anti-inflammatory action. However, chemical compounds responsible for this effect have not yet been identified. AIM OF THE STUDY: This study aimed to evaluate the antioxidant, antinociceptive and anti-inflammatory effects of the ethyl acetate fraction from the inner bark of P. pyramidalis. MATERIAL AND METHODS: Total phenol content (TP) was estimated using the Folin-Ciocalteu reagent, while in vitro antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Chemical identification was done using LC-PDA/MS and LC-ESI/MS/MS. In vivo antinociceptive and anti-inflammatory properties were investigated using formalin, mechanical hypernociception and carrageenan-induced pleurisy assays in mice. RESULTS: TP was 525.08 ± 17.49 µg mg-1 gallic acid equivalent. The ethyl acetate fraction (EAF) inhibited 87.76% of the DPPH radical with an EC50 of 22.94 µg mL-1 and Antioxidant Activity Index of 1.74. LC-PDA/MS and LC-ESI/MS/MS identified 15 compounds that are mostly derived from gallic and ellagic acids. Regarding in vivo antinociceptive and anti-inflammatory activity, EAF (100 mg kg-1) significantly reduced the nociceptive response in the second phase of the formalin assay by 50% (p < 0.01) compared with the control group. In the hypernociception test, a significant (p < 0.001) anti-hyperalgesic effect of EAF (100 mg kg-1) was observed up to the third hour of evaluation (p < 0.001). In the carrageenan assay, EAF (100 mg kg-1) was shown to inhibit protein extravasation, increase total leukocytes and neutrophils, and inhibit mononuclear cells. CONCLUSION: These results demonstrate EAF from the inner bark of P. pyramidalis has strong in vitro antioxidant effect as well as in vivo antinociceptive and anti-inflammatory activities, which may be attributed to the bark being rich in phenolic compounds derived from gallic acid.

Anti-hyperalgesic properties of a flavanone derivative Poncirin in acute and chronic inflammatory pain models in mice.

BACKGROUND: Poncirin is flavanone derivative (isolated from Poncirus trifoliata) with known pharmacological activities such as anti-tumor, anti-osteoporotic, anti-inflammatory and anti-colitic. The present study aimed to explore the anti-allodynic and anti-hyperalgesic potentials of poncirin in murine models of inflammatory pain. METHODS: The analgesic potential of poncirin was evaluated in formalin-, acetic acid-, carrageenan- and Complete Freund's Adjuvant (CFA)-induced inflammatory pain models in mice. Anti-allodynic and anti-hyperalgesic activities were measured using Von Frey filaments, Randall Selitto, hotplate and cold acetone tests. The serum nitrite levels were determined using Griess reagent. The Quantitative Real-time PCR (qRT-PCR) was performed to assess the effect of poncirin on mRNA expression levels of inflammatory cytokines and anti-oxidant enzymes. RESULTS: Intraperitoneal administration of poncirin (30 mg/kg) markedly reduced the pain behavior in both acetic acid-induced visceral pain and formalin-induced tonic pain models used as preliminary screening tools. The poncirin (30 mg/kg) treatment considerably inhibited the mechanical hyperalgesia and allodynia as well as thermal hyperalgesia and cold allodynia. The qRT-PCR analysis showed noticeable inhibition of pro-inflammatory cytokines (mRNA expression levels of TNF-α, IL-1ß and IL-6) (p < 0.05) in poncirin treated group. Similarly, poncirin treatment also enhanced the mRNA expressions levels of anti-oxidant enzymes such as transcription factor such as nuclear factor (erythroid-derived 2)-like 2 (Nrf2) (p < 0.05), heme oxygenase (HO-1) (p < 0.05) and superoxide dismutase (SOD2) (p < 0.05). Chronic treatment of poncirin for 6 days did not confer any significant hepatic and renal toxicity. Furthermore, poncirin treatment did not altered the motor coordination and muscle strength in CFA-induced chronic inflammatory pain model. CONCLUSION: The present study demonstrated that poncirin treatment significantly reduced pain behaviors in all experimental models of inflammatory pain, suggesting the promising analgesic potential of poncirin in inflammatory pain conditions.

Peltatoside Isolated from Annona crassiflora Induces Peripheral Antinociception by Activation of the Cannabinoid System.

Peltatoside is a natural compound isolated from leaves of Annona crassiflora Mart., a plant widely used in folk medicine. This substance is an analogue of quercetin, a flavonoid extensively studied because of its diverse biological activities, including analgesic effects. Besides, a previous study suggested, by computer structure analyses, a possible quercetin-CB1 cannabinoid receptor interaction. Thus, the aim of this work was to assess the antinociceptive effect of peltatoside and analyze the cannabinoid system involvement in this action. The mouse paw pressure test was used and hyperalgesia was induced by intraplantar injection of carrageenan (200 µg/paw). All used drugs were administered by intraplantar administration in Swiss male mice (n = 6). Peltatoside (100 µg/paw) elicited a local inhibition of hyperalgesia. The peripheral antinociceptive action of peltatoside was antagonized by the CB1 cannabinoid antagonist AM251 (160 µg/paw), but not by CB2 cannabinoid antagonist AM630 (100 µg/paw). In order to assess the role of endocannabinoids in this peripheral antinociceptive effect, we used (i) [5Z,8Z,11Z,14Z]-5,8,11,14-eicosatetraenyl-methyl ester phosphonofluoridic acid, an inhibitor of anandamide amidase; (ii) JZL184, an inhibitor for monoacylglycerol lipase, the primary enzyme responsible for degrading the endocannabinoid 2-arachidonoylglycerol; and (iii) VDM11, an endocannabinoid reuptake inhibitor. MAFP, JZL184, and VDM11 did not induce antinociception, respectively, at the doses 0.5, 3.8, and 2.5 µg/paw, however, these three drugs were able to potentiate the peripheral antinociceptive effect of peltatoside at an intermediary dose (50 µg/paw). Our results suggest that this natural substance is capable of inducing analgesia through the activation of peripheral CB1 receptors, involving endocannabinoids in this process.

Pimaradienoic Acid Inhibits Carrageenan-Induced Inflammatory Leukocyte Recruitment and Edema in Mice: Inhibition of Oxidative Stress, Nitric Oxide and Cytokine Production.

Pimaradienoic acid (PA; ent-pimara-8(14),15-dien-19-oic acid) is a pimarane diterpene found in plants such as Vigueira arenaria Baker (Asteraceae) in the Brazilian savannas. Although there is evidence on the analgesic and in vitro inhibition of inflammatory signaling pathways, and paw edema by PA, its anti-inflammatory effect deserves further investigation. Thus, the objective of present study was to investigate the anti-inflammatory effect of PA in carrageenan-induced peritoneal and paw inflammation in mice. Firstly, we assessed the effect of PA in carrageenan-induced leukocyte recruitment in the peritoneal cavity and paw edema and myeloperoxidase activity. Next, we investigated the mechanisms involved in the anti-inflammatory effect of PA. The effect of PA on carrageenan-induced oxidative stress in the paw skin and peritoneal cavity was assessed. We also tested the effect of PA on nitric oxide, superoxide anion, and inflammatory cytokine production in the peritoneal cavity. PA inhibited carrageenan-induced recruitment of total leukocytes and neutrophils to the peritoneal cavity in a dose-dependent manner. PA also inhibited carrageenan-induced paw edema and myeloperoxidase activity in the paw skin. The anti-inflammatory mechanism of PA depended on maintaining paw skin antioxidant activity as observed by the levels of reduced glutathione, ability to scavenge the ABTS cation and reduce iron as well as by the inhibition of superoxide anion and nitric oxide production in the peritoneal cavity. Furthermore, PA inhibited carrageenan-induced peritoneal production of inflammatory cytokines TNF-α and IL-1ß. PA presents prominent anti-inflammatory effect in carrageenan-induced inflammation by reducing oxidative stress, nitric oxide, and cytokine production. Therefore, it seems to be a promising anti-inflammatory molecule that merits further investigation.

Cyane-carvone, a synthetic derivative of carvone, inhibits inflammatory response by reducing cytokine production and oxidative stress and shows antinociceptive effect in mice.

Cyane-carvone (CC) was studied to elucidate its anti-inflammatory, antinociceptive, and antioxidant effects in Mus musculus. Anti-inflammatory (bradykinin, histamine, prostaglandin E2, serotonin, and carrageenan) and antinociceptive (acetic acid and formalin) models were utilized. Myeloperoxidase activity, interleukin (IL)-1ß, tumor necrosis factor alpha (TNF-α), and glutathione (GSH) levels were evaluated. Analysis of variance followed by Student-Newman-Keuls' test was done. Results were compared with control groups (significantly when p < 0.05). In bradykinin, histamine, prostaglandin E2, and serotonin tests, 75 mg/kg CC decreased significantly paw edema (t = 30, 60, 90, and/or 120 min). In carrageenan test, 50 and 75 mg/kg CC (t = 3 h and t = 4 h) and 25 mg/kg CC (t = 4 h) decreased significantly paw edema. CC (75 mg/kg) inhibited significantly mieloperoxidase activity and decreased IL-1ß and TNF-α, and all doses increased GSH levels. CC (75 mg/kg) decreased significantly the number of contortions of animals and time of licking (phase 2). CC showed anti-inflammatory, antinociceptive, and antioxidant effects in mice.

Locally injected dexmedetomidine inhibits carrageenin-induced inflammatory responses in the injected region.

BACKGROUND: Dexmedetomidine, a highly selective agonist of α2-adrenoceptors, is a commonly used sedative; however, a potent anti-inflammatory effect has also been found. In the present study we evaluated the inhibitory effect of locally injected dexmedetomidine on inflammatory responses in the injected region. METHODS: Local inflammation was induced in the hindpaws of male mice (aged 6-8 weeks) by intraplantar injection of lambda-carrageenin. To offset the central effect of tested agents, different agents were blindly injected into the left and right paws in the pairs of comparison. The effect of dexmedetomidine on edema (increase in paw volume), the accumulation of leukocytes, and production of tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2) were evaluated after carrageenin injection, using water displacement plethysmometry, histological imaging, immunohistochemistry, and Western blotting analysis. Furthermore, we also evaluated the effect of yohimbine, a full antagonist of α2-adrenoceptors, and phenylephrine, an agonist of the α1-adrenoceptor, on dexmedetomidine's action on inflammatory responses. RESULTS: Paw volume and amount of leukocytes in the injected region significantly increased after the injection of carrageenin. Similarly, TNF-α and COX-2 production was found in the subcutaneous region injected with carrageenin, 4 hours after injection. Dexmedetomidine significantly inhibited all increases in paw volume, leukocytes, and production of TNF-α and COX-2. Furthermore, yohimbine significantly antagonized the anti-inflammatory effects of dexmedetomidine, whereas phenylephrine did not significantly alter them. CONCLUSIONS: The findings suggest that locally injected dexmedetomidine exhibits an anti-inflammatory effect against local acute inflammatory responses, mediated by α2-adrenoceptors.

Improving the solubility of a new class of antiinflammatory pharmacodynamic hybrids, that release nitric oxide and inhibit cycloxygenase-2 isoenzyme.

The development of a novel class of pharmacodynamic hybrids that inhibits COX-2 isoform is reported. These molecules display enhanced nitric oxide releasing properties due to the presence of an ionisable moiety. The in vivo analgesic/anti-inflammatory activity was maintained in relation to the parent compounds.

Participation of the NO/cGMP/K+ATP pathway in the antinociception induced by Walker tumor bearing in rats

Implantation of Walker 256 tumor decreases acute systemic inflammation in rats. Inflammatory hyperalgesia is one of the most important events of acute inflammation. The L-arginine/NO/cGMP/K+ATP pathway has been proposed as the mechanism of peripheral antinociception mediated by several drugs and physical exercise. The objective of this study was to investigate a possible involvement of the NO/cGMP/K+ATP pathway in antinociception induced in Walker 256 tumor-bearing male Wistar rats (180-220 g). The groups consisted of 5-6 animals. Mechanical inflammatory hypernociception was evaluated using an electronic version of the von Frey test. Walker tumor (4th and 7th day post-implantation) reduced prostaglandin E2- (PGE2, 400 ng/paw; 50 µL; intraplantar injection) and carrageenan-induced hypernociception (500 µg/paw; 100 µL; intraplantar injection). Walker tumor-induced analgesia was reversed (99.3% for carrageenan and 77.2% for PGE2) by a selective inhibitor of nitric oxide synthase (L-NAME; 90 mg/kg, ip) and L-arginine (200 mg/kg, ip), which prevented (80% for carrageenan and 65% for PGE2) the effect of L-NAME. Treatment with the soluble guanylyl cyclase inhibitor ODQ (100% for carrageenan and 95% for PGE2; 8 µg/paw) and the ATP-sensitive K+ channel (KATP) blocker glibenclamide (87.5% for carrageenan and 100% for PGE2; 160 µg/paw) reversed the antinociceptive effect of tumor bearing in a statistically significant manner (P < 0.05). The present study confirmed an intrinsic peripheral antinociceptive effect of Walker tumor bearing in rats. This antinociceptive effect seemed to be mediated by activation of the NO/cGMP pathway followed by the opening of KATP channels.

Participation of the NO/cGMP/K+ATP pathway in the antinociception induced by Walker tumor bearing in rats.

Implantation of Walker 256 tumor decreases acute systemic inflammation in rats. Inflammatory hyperalgesia is one of the most important events of acute inflammation. The L-arginine/NO/cGMP/K(+)ATP pathway has been proposed as the mechanism of peripheral antinociception mediated by several drugs and physical exercise. The objective of this study was to investigate a possible involvement of the NO/cGMP/K(+)ATP pathway in antinociception induced in Walker 256 tumor-bearing male Wistar rats (180-220 g). The groups consisted of 5-6 animals. Mechanical inflammatory hypernociception was evaluated using an electronic version of the von Frey test. Walker tumor (4th and 7th day post-implantation) reduced prostaglandin E(2)- (PGE(2), 400 ng/paw; 50 µL; intraplantar injection) and carrageenan-induced hypernociception (500 µg/paw; 100 µL; intraplantar injection). Walker tumor-induced analgesia was reversed (99.3% for carrageenan and 77.2% for PGE(2)) by a selective inhibitor of nitric oxide synthase (L-NAME; 90 mg/kg, ip) and L-arginine (200 mg/kg, ip), which prevented (80% for carrageenan and 65% for PGE(2)) the effect of L-NAME. Treatment with the soluble guanylyl cyclase inhibitor ODQ (100% for carrageenan and 95% for PGE(2); 8 µg/paw) and the ATP-sensitive K(+) channel (KATP) blocker glibenclamide (87.5% for carrageenan and 100% for PGE(2); 160 µg/paw) reversed the antinociceptive effect of tumor bearing in a statistically significant manner (P < 0.05). The present study confirmed an intrinsic peripheral antinociceptive effect of Walker tumor bearing in rats. This antinociceptive effect seemed to be mediated by activation of the NO/cGMP pathway followed by the opening of KATP channels.

Inflammation mobilizes local resources to control hyperalgesia: the role of endogenous opioid peptides.

The aim of the present study was to investigate the mechanisms underlying the endogenous control of nociception at a peripheral level during inflammation. Using a pharmacological approach and the rat paw pressure test, we assessed the effect of an intraplantar injection of naloxone, an opioid receptor antagonist, and bestatin, an aminopeptidase inhibitor, on hyperalgesia induced by carrageenan, which mimics an inflammatory process, or prostaglandin E(2) (PGE(2)), which directly sensitizes nociceptors. Naloxone induced a significant and dose-dependent (25, 50 or 100 µg) increase in carrageenan-induced hyperalgesia, but not PGE(2)-induced hyperalgesia. Bestatin (400 µg/paw) significantly counteracted carrageenan-induced hyperalgesia, inducing an increase in the nociceptive threshold compared to control, but it did not modify hyperalgesia induced by PGE(2) injection into the rat paw. Positive ß-endorphin immunoreactivity was increased in paw inflammation induced by carrageenan in comparison with the control group. However, PGE(2) did not significantly alter the immunostained area. These results provide evidence for activation of the endogenous opioidergic system during inflammation and indicate that this system regulates hyperalgesia through a negative feedback mechanism, modulating it at a peripheral level.

Interactions of estradiol and NSAIDS on carrageenan-induced hyperalgesia.

How exogenous estrogen affects inflammatory responses is poorly understood despite the large numbers of women receiving estrogen-alone hormone therapy. The aim of this study was to determine if estradiol alters injury- or inflammation-induced nociceptive responses after carrageenan administration in females and whether its effects are mediated through cyclo-oxygenase (COX) and prostaglandins (PG). To this end, paw withdrawal latencies and serum levels of PGE2 and PGD2 were measured in rats treated with estradiol (0, 10, 20, and 30%) and/or SC560 (COX-1 inhibitor) or NS398 (COX-2 inhibitor) after intraplantar carrageenan administration. Estradiol significantly increased withdrawal latencies before (baseline condition) and after carrageenan administration to one hindpaw. NS398 was anti-nociceptive only in carrageenan treated animals. SC560 increased withdrawal latencies in both paws at 1 and 5hours after carrageenan administration. Co-administration of estradiol and NS398, but not SC560, was additive except for a prolonged anti-nociceptive effects of estradiol combined with NS398. The anti-nociceptive effect extended beyond that observed with either drug or estradiol alone at the 5-hour time point. Estradiol had no significant effect on PGE2 serum levels, but both COX antagonists decreased them. Although neither estradiol nor the COX inhibitors alone had an effect on PGD2 serum levels, co-administration of NS398 and estradiol significantly elevated PGD2 levels. Taken together, our results suggest that estradiol is anti-nociceptive in the thermal test and reduces carrageenan-induced hyperalgesia. These effects are minimally altered through PG-mediated mechanisms.

Treatment with ketanserin produces opioid-mediated hypoalgesia in the late phase of carrageenan-induced inflammatory hyperalgesia in rats.

Both pro-nociceptive and antinociceptive mediators are released in the tissues during inflammation. Balance of these two types of mediators determines the induction and maintenance of pain or hypernociception. This study was designed to explore whether 5-HT(2A) receptors in the periphery contributed to the maintenance of carrageenan-evoked hyperalgesia. Intraplantar (i.pl.) injection of carrageenan evoked hyperalgesia detected by noxious heat stimulus. The 5-HT(2A) receptor antagonist ketanserin administered i.pl. 1 h after carrageenan dose-dependently (2-20 microg) prolonged paw withdrawal latency (PWL) during the late phase (24 h) of carrageenan-evoked inflammation. Following treatments with carrageenan and ketanserin, i.pl. injection of formalin (1%) produced significantly fewer nocifensive behaviors and expression of c-Fos protein in the spinal dorsal horn, confirming the hypoalgesic status in the inflamed site. However, injection of ketanserin in naive site failed to produce hypoalgesia. The hypoalgesia was completely abolished by local or systemic injection of naloxone methiodide. The present study suggests that 5-HT(2A) receptors were involved in the maintenance of inflammatory pain, and that 5-HT suppressed inflammation-associated endogenous opioid analgesia contributing to its pro-nociceptive actions in the periphery. It implied a possible therapeutic benefit of blockade of local 5-HT(2A) receptors in the treatment of inflammatory pain.

Lipoxygenase inhibitors suppressed carrageenan-induced Fos-expression and inflammatory pain responses in the rat.

Lipoxygenase (LO) metabolites are generated in inflamed tissues. However, it is unclear whether the inhibition of the LO activity regulates the expression of c-Fos protein, a pain marker in the spinal cord. Here we used a carrageenan-induced inflammation model to examine the role of LO in the development of c-Fos expression. Intradermally injected carrageenan caused elevated number of cells exhibiting Fos-like immunoreactivity (Fos-LI) in the spinal dorsal horn, and decreased the thermal and mechanical threshold in Hargreaves and von Frey tests. Pretreatment with an inhibitor of phospholipase A2, that generates the LO substrate, prior to the carrageenan injection significantly reduced the number of Fos-(+) cells. A general LO inhibitor NDGA, a 5-LO inhibitor AA-861 and a 12-LO inhibitor baicalein also exhibited the similar effects. Moreover, the LO inhibitors suppressed carrageenan-induced thermal and mechanical hyperalgesic behaviors, which inidcates that the changes in Fos expression correlates with those in the nociceptive behaviors in the inflamed rats. LO products are endogenous TRPV1 activators and pretreatment with BCTC, a TRPV1 antagonist inhibited the thermal but not the mechanical hypersensitivity. Overall, our results from the Fos-LI and behavior tests suggest that LO products released from inflamed tissues contribute to nociception during carrageenan-induced inflammation, indicating that the LO pathway is a possible target for modulating inflammatory pain.

Nociceptive inhibition prevents inflammatory pain induced changes in the blood-brain barrier.

Previous studies by our group have shown that peripheral inflammatory insult, using the lambda-carrageenan inflammatory pain (CIP) model, induced alterations in the molecular and functional properties of the blood-brain barrier (BBB). The question remained whether these changes were mediated via an inflammatory and/or neuronal mechanism. In this study, we investigated the involvement of neuronal input from pain activity on alterations in BBB integrity by peripheral inhibition of nociceptive input. A perineural injection of 0.75% bupivacaine into the right hind leg prior to CIP was used for peripheral nerve block. Upon nerve block, there was a significant decrease in thermal allodynia induced by CIP, but no effect on edema formation 1 h post-CIP. BBB permeability was increased 1 h post-CIP treatment as determined by in situ brain perfusion of [(14)C] sucrose; bupivacaine nerve block of CIP caused an attenuation of [(14)C] sucrose permeability, back to saline control levels. Paralleling the changes in [(14)C] sucrose permeability, we also report increased expression of three tight junction (TJ) proteins, zonula occluden-1 (ZO-1), occludin and claudin-5 with CIP. Upon bupivacaine nerve block, changes in expression were prevented. These data show that the lambda-carrageenan-induced changes in [(14)C] sucrose permeability and protein expression of ZO-1, occludin and claudin-5 are prevented with inhibition of nociceptive input. Therefore, we suggest that nociceptive signaling is in part responsible for the alteration in BBB integrity under CIP.

Antinociceptive effect of CNS peroxynitrite scavenger in a mouse model of orofacial pain.

Peroxynitrite (ONOO(-)) and species derived from it can oxidize and nitrate lipids, proteins and DNA leading to changes in signaling molecules. The present study was carried out to elucidate possible effects of CNS peroxynitrite in a mouse model of orofacial pain. Mice that received facial carrageenan injection + intracerebroventricular (i.c.v.) injection of the peroxynitrite scavenger [5,10,15,20-Tetrakis (4-sulfonatophenyl) porphyrinato iron (III), chloride] (FeTPPS) showed significantly fewer face wash strokes upon probing the inflamed area of the face with a von Frey hair at 6 h after injection, compared to mice that received facial carrageenan alone, or facial carrageenan injection + i.c.v. injection of saline. Mice that received i.c.v. injection of FeTPPS without facial carrageenan injection showed no significant difference in response to von Frey hair stimulation, compared to mice that received i.c.v. injection of saline without facial carrageenan injection. These results indicate an anti-nociceptive effect of the peroxynitrite scavenger FeTPPS in carrageenan induced facial pain but no effect on normal tactile sensation and point to an important role of CNS peroxynitrite in nociception.

Inhibition of carrageenan-induced edema by tripleurospermum disciforme extract in rats.

In this research anti-inflammatory effect of Tripleurospermum disciforme extract was studied in rats. The effect of the extract against acute inflammation was studied by hind paw edema test. Intraperitoneal injection of different doses (15, 30, 45, 60, 90 and 120 mg kg(-1)) of Tripleurospermum disciforme which was followed by hind paw carageenan injection 1 h later were investigated. The resultant edema was quantified by measuring changes of diameter of hind foot. After 2, 3, 4 and 6 h we measured the anti-inflammatory effect of Tripleurospermum disciforme extract. Tripleurospermum disciforme extract with doses of 45, 60, 90 and 120 mg kg(-1) and indomethacin 5 mg kg(-1) showed significant effect. It is concluded that Tripleurospermum disciforme extract has anti-inflammatory effect against acute inflammation.

Anti-hyperalgesic effects of intrathecally administered neuropeptide W-23, and neuropeptide B, in tests of inflammatory pain in rats.

Neuropeptide W-23 (NPW23) is an endogenous ligand of both GPR7 and GPR8, and neuropeptide B (NPB) is an endogenous ligand of GPR7. GPR7 mRNA has been detected in regions of the cortex, the hippocampus, the hypothalamus, and the spinal cord in the rat, but GPR8 has not been found in rodents. GPR7 and GPR8 receptors have structural features in common with both opioid and somatostatin receptors. The effects of intrathecal (i.t.) application of NPW23 and NPB were tested in two inflammatory pain models (plantar injection of formalin or carrageenan) and two thermal nociceptive tests (52.5 degrees C and 50.5 degrees C hot plates) and one mechanical nociceptive test in the rat. I.t. injection of either NPW23 or NPB decreased the number of agitation behaviors induced by paw formalin injection and attenuated the level of mechanical allodynia, but not the level of thermal hyperalgesia, induced by paw carrageenan injection in a dose-dependent manner at a dose between 0.1 and 10 microg, significantly. The effects of either 10 microg of NPW23 or 10 microg of NPB were not antagonized by 10 microg of naloxone. I.t. injection of either NPW23 or NPB had no effect in both the 52.5 degrees C hot plate test or in the 50.5 degrees C hot plate tests at a dose between 1 and 100 microg. I.t. injection of either 10 microg of NPW23 or 10 microg of NPB had no effect in the mechanical nociceptive test. I.t. injection of either 10 microg of NPW23 or 10 microg of NPB significantly suppressed the expression of Fos-like immunoreactivity of the L4-5 spinal dorsal horn induced by paw formalin injection. These data suggest that both spinally-applied NPW23 and NPB suppressed the input of nociceptive information to the spinal dorsal horn, produced an analgesic effect in the formalin test, and attenuated the level of mechanical allodynia in the carrageenan test, and that either spinally applied NPW23 or spinally applied NPB had no effect in the physiological condition.

Synthesis and biological evaluation of 2-thiopyrimidine derivatives.

Various 2-thiopyrimidine derivatives have been synthesized by an efficient, one-pot reaction of functionalized amines with either 4-isothiocyanato-4-methyl-2-pentanone or 3-isothiocyanatobutanal. All the synthesized compounds were fully characterized by elemental analysis (CHN), FT-IR, (1)H NMR, and mass spectral data. One of the compounds, 7,7,8a-trimethyl-hexahydro-thiazolo[3,2-c]pyrimidine-5-thione (17) showed good anti-inflammatory (37.4% at 100 mg/kg p.o.) and analgesic activity (75% at 100 mg/kg p.o.). 7-(1-Mercapto-3,3,4a-trimethyl-4,4a,5,9b-tetrahydro-3H-pyrido[4,3-b]indol-7-yl)-3,3,4a-trimethyl-3,4,4a,5-tetrahydro-benzo[4,5]imidazo[1,2-c]pyrimidine-1-thiol (3) showed moderate activity against CDK-1 (IC(50)=5 microM). The other compounds showed moderate anti-inflammatory (5-20%), analgesic (25-75%) and protein kinase (CDK-5, GSK-3) inhibitory activities (IC(50)> 10 microM).

Raloxifene, a selective estrogen receptor modulator, reduces carrageenan-induced acute inflammation in normal and ovariectomized rats.

Raloxifene (RAL) is a selective estrogen receptor modulator presenting tissue-specific agonist activity. The aim of this study was to examine whether RAL has an estrogenic effect on carrageenan-induced acute inflammation. Adult female rats were ovariectomized (OVX) 7 wk before edema or pleurisy to deplete circulating estrogens. Edema formation and selected inflammatory markers in inflamed paw tissue were measured in intact (sham-operated) and OVX rats. Groups of OVX rats were treated with RAL (1, 3, or 10 mg/kg) or 17beta-estradiol (E2, 25 microg/kg), and these treatments began 2 d after surgery and continued until carrageenan paw edema or pleurisy. Ovariectomy amplifies the inflammation, and we found that RAL, as well as E2, attenuates inflammation and tissue damage associated with paw edema and pleurisy. In treated rats, there is a decrease in edema development and formation, and in polymorphonuclear cell infiltration and migration, as shown by myeloperoxidase measurement and cell counting. RAL and E2 treatments decrease cyclooxygenase-2 and inducible nitric oxide synthase expression in inflamed areas and counteract the inhibition of peroxisome proliferators-activated receptor-gamma expression caused by ovariectomy, restoring this receptor protein expression to sham-operated levels and identifying a possible peroxisome proliferators-activated receptor-dependent antiinflammatory effect of these drugs. Moreover, RAL and E2 increase cytoprotective heat shock protein 72 expression, which seems to be closely associated with the remission of the inflammatory reaction. In addition, we confirm the antiinflammatory effect of RAL in male rats, using a single administration of RAL or E2.

Evidence for the involvement of endogenous ATP and P2X receptors in TMJ pain.

Evidence is accumulating which supports a role for ATP in the initiation of pain by acting on P2X receptors expressed on nociceptive afferent nerve terminals. To investigate whether these receptors play a role in temporomandibular (TMJ) pain, we studied the presence of functional P2X receptors in rat TMJ by examining the nociceptive behavioral response to the application of the selective P2X receptor agonist alpha,beta-methylene ATP (alpha,beta-meATP) into the TMJ region of rat. The involvement of endogenous ATP in the development of TMJ inflammatory hyperalgesia was also determined by evaluating the effect of the general P2 receptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on carrageenan-induced TMJ inflammatory hyperalgesia. Application of alpha,beta-meATP into the TMJ region of rats produced significant nociceptive responses that were significantly reduced by the co-application of lidocaine N-ethyl bromide quaternary salt, QX-314, (2%) or of the P2 receptor antagonist PPADS. Co-application of PPADS with carrageenan into the TMJ significantly reduced inflammatory hyperalgesia. The results indicate that functional P2X receptors are present in the TMJ and suggest that endogenous ATP may play a role in TMJ inflammatory pain mechanisms possibly by acting primarily in these receptors.