Geographical variation in the chemical composition, anti-inflammatory activity of the essential oil, micromorphology and histochemistry of Schinus terebinthifolia Raddi.

ETHNOPHARMACOLOGICAL RELEVANCE: Schinus terebinthifolia Raddi (Anacardiaceae) is rich in essential oil, distinguished by a predominance of monoterpenes and sesquiterpenes, it being widely used in traditional medicine for the treatment of inflammations. AIM OF STUDY: This study's objective was to investigate the chemical composition of the essential oil of S. terebinthifolia (EOST) collected in six states of Brazil, evaluate its anti-inflammatory effects in mice, and analyze the histochemistry and micromorphology of leaves and stems. MATERIALS AND METHODS: Aerial parts of S. terebinthifolia were collected in six states of Brazil, and the essential oil was extracted by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The histochemistry and micromorphology of leaves and stems were performed using standard reagents, light and field emission scanning electron microscopy, beyond energy-dispersive X-ray spectroscopy. The EOST were evaluated for anti-inflammatory activity and hyperalgesia using the carrageenan-induced paw edema methodology. RESULTS: The EOST showed variation across the six states in its yield (0.40%-0.86%) and chemical composition: hydrocarbon monoterpenes (28.76%-47.73%), sesquiterpenes, (31.43%-41.76%), oxygenated monoterpenes (14.31%-19.57%), and oxygenated sesquiterpenes (4.87%-14.38%). Both α-pinene and limonene were predominant constituents of essential in five regions, except for one state where α-phellandrene and limonene were the dominant components. A comprehensive description of the leaf and stem micromorphology and histochemistry was performed. In the in vivo testing, all EOST samples exerted antiedematogenic and anti-hyperalgesic effects, when tested in a carrageenan-induced paw inflammation (mechanical and thermal hyperalgesia) model with oral doses of 30 mg/kg. CONCLUSION: Our results indicate that the EOST samples collected in six Brazilian states differed in their chemical composition but not their anti-inflammatory and antihyperalgesic effects, which was correlated with the synergistic effect of its components, collaborating the etnhopharmacologycal use of this plant due to its an anti-inflammatory effect. Also, micromorphology and histochemistry of leaves and stems presented in this study provide anatomical and microchemical information, which aids species identification.

Electroacupuncture Regulates Pain Transition Through Inhibiting PKCε and TRPV1 Expression in Dorsal Root Ganglion.

Many cases of acute pain can be resolved with few side effects. However, some cases of acute pain may persist beyond the time required for tissue injury recovery and transit to chronic pain, which is hard to treat. The mechanisms underlying pain transition are not entirely understood, and treatment strategies are lacking. In this study, the hyperalgesic priming model was established on rats to study pain transition by injection of carrageenan (Car) and prostaglandin E2 (PGE2). The expression levels of protein kinase C epsilon (PKCε) and transient receptor potential vanilloid 1 (TRPV1) in the L4-L6 dorsal root ganglion (DRG) were investigated. Electroacupuncture (EA) is a form of acupuncture in which a small electric current is passed between a pair of acupuncture needles. EA was administrated, and its effect on hyperalgesia and PKCε and TRPV1 expression was investigated. The PKCε-TRPV1 signaling pathway in DRG was implicated in the pain transition. EA increased the pain threshold of model animals and regulated the high expression of PKCε and TRPV1. Moreover, EA also regulated hyperalgesia and high TRPV1 expression induced by selective PKCε activation. We also found that EA partly increased chronic pain threshold, even though it was only administered between the Car and PGE2 injections. These findings suggested that EA could prevent the transition from acute to chronic pain by inhibiting the PKCε and TRPV1 expression in the peripheral nervous system.

Electroacupuncture alleviates the transition from acute to chronic pain through the p38 MAPK/TNF-α signalling pathway in the spinal dorsal horn.

BACKGROUND: Hyperalgesic priming (HP) is a model of the transition from acute to chronic pain. Electroacupuncture (EA) could inhibit pain development through the peripheral dorsal root ganglia; however, it is unclear whether it can mitigate the transition from acute to chronic pain by attenuating protein expression in the p38 MAPK (mitogen-activated protein kinase)/tumour necrosis factor alpha (TNF-α) pathway in the spinal dorsal horn. AIMS: We aimed to determine whether EA could prevent the transition from acute to chronic pain by affecting the p38 MAPK/TNF-α pathway in the spinal dorsal horn in a rat model established using HP. METHODS: We first randomly subdivided 30 male Sprague-Dawley (SD) rats into 5 groups (n = 6 per group): control (N), sham HP (Sham-HP), HP, HP + SB203580p38 MAPK (HP+SB203580), and HP + Lenalidomide (CC-5013) (HP+Lenalidomide). We then randomly subdivided a further 30 male SD rats into 5 groups (n = 6 per group): Sham-HP, HP, sham EA (Sham EA), EA (EA), and EA + U-46619 p38 MAPK agonist (EA+U-46619). We assessed the effects of EA on the mechanical paw withdrawal threshold and p38 MAPK/TNF-α expression in the spinal dorsal horn of rats subjected to chronic inflammatory pain. RESULTS: Rats in the EA group had reduced p38 MAPK and TNF-α expression and had significantly reduced mechanical hyperalgesia compared with rats in the other groups. CONCLUSION: Our findings indicate that EA could increase the mechanical pain threshold in rats and inhibit the transition from acute pain to chronic pain. This mechanism could involve reduced p38 MAPK/TNF-α expression in the spinal dorsal horn.

Role of GABAAR in the Transition From Acute to Chronic Pain and the Analgesic Effect of Electroacupuncture on Hyperalgesic Priming Model Rats.

Chronic pain is a costly health problem that impairs health-related quality of life when not effectively treated. Regulating the transition from acute to chronic pain is a new therapeutic strategy for chronic pain that presents a major clinical challenge. The underlying mechanisms of pain transition are not entirely understood, and strategies for preventing this transition are lacking. Here, a hyperalgesic priming model was used to study the potential mechanism by which γ-aminobutyric acid receptor type A (GABAAR) in the dorsal root ganglion (DRG) contributes to pain transition. Furthermore, electroacupuncture (EA), a modern method of acupuncture, was administered to regulate pain transition, and the mechanism underlying EA's regulatory effect was investigated. Hyperalgesic priming was induced by intraplanar injection of carrageenan (Car)/prostaglandin E2 (PGE2). The decrease in mechanical withdrawal threshold (MWT) induced by PGE2 returned to baseline 4 h after injection in NS + PGE2 group, and still persisted 24 h after injection in Car + PGE2 group. Lower expression of GABAAR in the lumbar DRG was observed in the model rats. Furthermore, activating or blocking GABAAR could reversed the long-lasting hyperalgesia induced by Car/PGE2 injection or produced a persistent hyperalgesia. In addition, GABAAR may be involved in Protein Kinase C epsilon (PKCε) activation in the DRG, a mark molecular of pain transition. EA considerably increased the mechanical pain thresholds of hyperalgesic priming model mammals in both the acute and chronic phases. Furthermore, EA upregulated the expression of GABAAR and inhibited the activation of PKCε in the DRG. In addition, peripheral administration of picrotoxin blocked the analgesic effect of EA on the model rats and abolished the regulatory effect of EA on PKCε activation. These findings suggested that GABAAR plays a key role in both the transition from acute to chronic pain and the analgesic effect of EA on hyperalgesic priming.

Analgesic and anti-inflammatory articular effects of essential oil and camphor isolated from Ocimum kilimandscharicum Gürke leaves.

ETHNOPHARMACOLOGICAL RELEVANCE: Leaves from Ocimum kilimandscharicum Gürke (Lamiaceae) are popularly used against articular pain. AIM OF STUDY: The aim of this study was to test the anti-inflammatory and anti-hyperalgesic (analgesic) properties of the essential oil and camphor isolated from O. Kilimandscharicum leaves (EOOK) in 4 models including zymosan induced-articular inflammation model in mice. MATERIAL AND METHODS: For in vivo models, EOOK was tested in carrageenan-induced paw edema model with oral doses of 30, 100, and 300 mg/kg (oral administration = p.o.) and in zymosan-induced articular inflammation (including knee edema, leukocyte infiltration, mechanical hyperalgesia and nitric oxide), EOOK (100 mg/kg, p. o.) and camphor (30 mg/kg, p. o.) were tested. EOOK (100 mg/kg, p. o.) was tested in the rolling and also in the adhesion of leukocytes to the mesenteric microcirculation in situ model of carrageenan induced inflammation and EOOK (1, 3, 10, 30, and 60 µg/mL) was tested in vitro against neutrophils chemotaxis induced by N-formyl methionyl leucyl phenylalanine (fMLP). RESULTS: The treatment with EOOK significantly inhibited the carrageenan-induced edema, mechanical and cold hyperalgesia. Both, EOOK and camphor inhibited all articular parameters induced by zymosan. In situ intravitral microscopy analysis, EOOK significantly inhibited carrageenan-induced leukocyte rolling and adhesion. In vitro neutrophils chemotaxis, EOOK inhibited the leukocyte chemotaxis induced by fMLP. CONCLUSIONS: The present study showed that EOOK inhibited pain and inflammatory parameters contributing, at least in part, to explain the popular use of this plant as analgesic natural agent. This study also demonstrates that camphor and some known anti-inflammatory compounds present in EOOK could contribute for analgesic and anti-inflammatory articular properties.

Electroacupuncture Regulates Pain Transition by Inhibiting the mGluR5-PKCε Signaling Pathway in the Dorsal Root Ganglia.

BACKGROUND: Acute pain can transition to chronic pain, presenting a major clinical challenge. Electroacupuncture (EA) can partly prevent the transition from acute to chronic pain. However, little is known about the mechanisms underlying the effect of EA. This study investigated the effect of EA on pain transition and the activation of metabotropic glutamate receptor 5 (mGluR5)-protein kinase C epsilon (PKCε) signaling pathway in the dorsal root ganglia (DRG). METHODS: The hyperalgesic priming model was established by the sequential intraplantar injection of carrageenan (1%, 100 µL) and prostaglandin E2 (PGE2) into the left hind paw of rats. EA treatment (2/100 Hz, 30 min, once/day) was applied at bilateral Zusanli (ST36) and Kunlun (BL60) acupoints in rats. Von Frey filaments were used to investigate the mechanical withdrawal threshold (MWT) at different time points. The protein expression levels of mGluR5 and PKCε in the ipsilateral L4-L6 DRGs of rats were detected by Western blot. Some pharmacological experiments were performed to evaluate the relationship between mGluR5, PKCε and the MWT. It was also used to test the effects of EA on the expression levels of mGluR5 and PKCε and changes in the MWT. RESULTS: Sequential injection of carrageenan and PGE2 significantly decreased the MWT of rats and up-regulated the expression level of mGluR5 and PKCε in the ipsilateral L4-L6 DRGs. EA can reverse the hyperalgesic priming induced by sequential injection of carrageenan/PGE and down-regulate the protein expression of mGluR5 and PKCε. Glutamate injection instead of PGE2 can mimic the hyperalgesic priming model. Pharmacological blocking of mGluR5 with specific antagonist MTEP can prevent the hyperalgesic priming and inhibit the activation of PKCε in DRGs. Furthermore, EA also produced analgesic effect on the hyperalgesic priming rats induced by carrageenan/mGluR5 injection and inhibited the high expression of PKCε. Sham EA produced none analgesic and regulatory effect. CONCLUSION: EA can regulate pain transition and it may relate with its inhibitory effect on the activation of mGluR5-PKCε signaling pathway in the DRGs.

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.

Analgesic and Anti-inflammatory Effects of Caryocar brasiliense.

BACKGROUND: Caryocar brasiliense, popularly known as pequi, is widely distributed in the Amazon rainforest and Brazilian savannah. The fruit obtained from pequi is used in cooking and has folk use as an anti-inflammatory and for the treatment of respiratory disease. Until now, these two properties had not been scientifically demonstrated for Pequi oil in a carrageenan model. OBJECTIVE: Our group determined the composition and safe use of Pequi oil from the Savannah of Campo Grande, and the anti-inflammatory and anti-nociceptive activities of this pequi oil were investigated in vivo models. MATERIALS AND METHODS: Doses of 300, 700, and 1000 mg/kg of Pequi oil were administered orally (p.o.) to Swiss male mice, and three parameters of inflammation (mechanical hyperalgesia, cold, hyperalgesia, and oedema) were analyzed in a carrageenan model to induce an inflammatory paw state. RESULTS AND DISCUSSION: The effects of Pequi oil were also carrageenan in pleurisy model, formalin, and acetic acid induced nociception. Oral administration of 1,000 mg/kg orally Pequi oil (p.o.) inhibited (*P<0.05), the migration of total leukocytes, but not alter plasma extravasation, in the pleurisy model when compared to control groups. The paw edema was inhibited with doses of 700 (P <0.05) and 1,000 mg (P<0.001) of pequi oil after 1, 2, and 4 hours after carrageenan. Pequi oil (1,000 mg/kg) also blocked the mechanical hyperalgesy and reduced cold allodynia induced by carrageenan in paw (P <0.05). Pequi oil treatment (1,000 mg/kg) almost blocked (P < 0.001) all parameters of nociception observed in formalin and acid acetic test. CONCLUSION: This is the first time that the analgesic and anti-inflammatory effects of Pequi oil have been shown.

[Advances of researches on peripheral PKCε pathway during transformation from acute to chronic pain and possibility of application of electroacupuncture intervention].

Protein kinase Cε (PKCε) is a transforming oncogene and plays an important role in many cellular processing. In the present paper, we review the development of experimental researches on the acute-chronic pain transformation. Results indicated that prostaglandin E2 (PGE2) / EP1 receptor-Gq-PKCε is an important signaling pathway to modulate chronic pain in peripheral dorsal root ganglion (DRG) neurons, and also plays a role in the later stage of hyperalgesia during transformation from acute to chronic pain. PKCε in DRG neurons induces mechanical and thermal hypersensitivity respectively by over expression of transient receptor potential vanilloid 1 (TRPV1) and TRP ankyrin-1 (TRPA1), further mediating the transformation from acute to chronic pain. Whereas, PGE2-evoked activation of EP1-Gq-PKCε signaling may be the key link in initiating the pain translation process through regulating downstream TRPA1 and TRPV1. Electroacupuncture (EA) has been used to effectively relieving various types of acute and chronic pain for decades, and can significantly inhibit the expression of PKCε and its upstream and downstream molecules. Therefore, it can be inferred that there exists a possibility of EA interventions in interfering the transformation from acute to chronic pain by regulating peripheral PKCε signaling pathway.

Anti-inflammatory Activity of Methanolic Extract and an Alkaloid from Palicourea crocea (Sw.) Roem and Schult.

Palicourea crocea (Sw.) Roem. and Schult., "douradinha," are used by treat inflammation (edema). Croceaine A (PC-1) was isolated from P. crocea (MEPC) leaves and studied for its antioxidant and anti-inflammatory activity, as well as concentrations of constituents and acute toxicity. The phenols and polyphenolics compounds and HPLC/DAD were determined. The antioxidant activity were evaluated for DPPH, ABTS, and MDA. MEPC (300, 100, and 300 mg/kg) and PC-1 (10 and 30 mg/kg) were tested for anti-inflammatory effects in paw edema, pleurisy, cold sensitivity, and mechanical hyperalgesia. Acute toxicity is also described. MEPC contained high concentrations of phenolic and flavonoid compounds (≤ 800.35 mg/g), as well as caffeic acid, ferulic acid, rutin, and quercetin, revealed by HPLC-DAD analysis. MEPC displayed antioxidant activity against ABTS radicals (IC50 = 68.5 µg/mL) and MDA (74%). MEPC and alkaloid PC-1 demonstrated an anti-edematogenic effect in Cg-induced paw edema in 2 and 4 h, and also significantly reduced mechanical hyperalgesia, cold response to acetone in mice, at 3 and 4 h after injection, as well as leukocyte migrationin the pleurisy model. No toxicity was detected by MEPC. For the first time, P. crocea was evaluated for its antioxidant, systemic anti-inflammatory, and anti-hyperalgesic activities.

Advances of researches on peripheral PKCε pathway during transformation from acute to chronic pain and possibility of application of electroacupuncture intervention / 针刺研究

Protein kinase Cε (PKCε) is a transforming oncogene and plays an important role in many cellular processing. In the present paper, we review the development of experimental researches on the acute-chronic pain transformation. Results indicated that prostaglandin E2 (PGE2) / EP1 receptor-Gq-PKCε is an important signaling pathway to modulate chronic pain in peripheral dorsal root ganglion (DRG) neurons, and also plays a role in the later stage of hyperalgesia during transformation from acute to chronic pain. PKCε in DRG neurons induces mechanical and thermal hypersensitivity respectively by over expression of transient receptor potential vanilloid 1 (TRPV1) and TRP ankyrin-1 (TRPA1), further mediating the transformation from acute to chronic pain. Whereas, PGE2-evoked activation of EP1-Gq-PKCε signaling may be the key link in initiating the pain translation process through regulating downstream TRPA1 and TRPV1. Electroacupuncture (EA) has been used to effectively relieving various types of acute and chronic pain for decades, and can significantly inhibit the expression of PKCε and its upstream and downstream molecules. Therefore, it can be inferred that there exists a possibility of EA interventions in interfering the transformation from acute to chronic pain by regulating peripheral PKCε signaling pathway.

Discovery of {4-[4,9-bis(ethyloxy)-1-oxo-1,3-dihydro-2H-benzo[f]isoindol-2-yl]-2-fluorophenyl}acetic acid (GSK726701A), a novel EP4 receptor partial agonist for the treatment of pain.

A novel series of EP4 agonists and antagonists have been identified, and then used to validate their potential in the treatment of inflammatory pain. This paper describes these novel ligands and their activity within a number of pre-clinical models of pain, ultimately leading to the identification of the EP4 partial agonist GSK726701A.

[Effect of Electroacupuncture on Pain Reaction and Content of Proteinase-activated Receptors 2 in Dorsal Root Ganglion in Hyperalgesia Rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on mechanical hyperalgesia threshold (MHTs) and thermal hyperalgesia threshold (THTs) and content of proteinase-activated receptors 2 (PAR 2) in dorsal root ganglia (DRG) in rats with inflammatory pain, so as to explore its peripheral mechanism underlying improvement of inflammatory pain. METHODS: The present study contains two parts. 1) In the first part, 27 male SD rats were randomized into sham hyperalgesic priming (sham-HP) group and real hyperalgesic priming (HP) group (n＝5 in the sham-HP group and n＝6 in the HP group for the test of MHTs, n＝8 in the two groups for the test of THTs). The sham-HP model was established by subcutaneous injection of normal saline into the left plantar part of the hind-paw, and the HP model established by subcutaneous injection of 1% carragenan (the first injection) into the same left hind paw, followed by injection of PGE2 (100 ng/25 µL, the second injection) into the dorsum pedis of the same hind paw 7 days after the first injection. The ipsilateral paw withdrawal latencies (MHTs and THTs) were detected before and 5 h, 3 d and 6 d after the first injection, 0.5, 4 and 24 h after the second injection. 2) In the second part, 64 male SD rats were randomly divided into sham-HP, HP, sham-EA and EA groups (n＝16 in each group). The sham-HP and HP models were made in the same way as the first part. Both"Zusanli"(ST 36)and "Kunlun"(BL 60) were punctured with filiform needles in the sham-EA group and also stimulated with EA: 2 Hz/100 Hz, 0.5－1.5 mA (0.5 mA increase per 10 min) for 30 min in the EA group, 1 time/d for 7 d. Both ipsilateral MHTs and THTs were observed at the same time-points of the first part and the PAR 2 protein content in the L 4－L 6 DRGs was assayed by ELISA 24 h after the second injection. RESULTS: 1) In the first part of the study, compared with the sham-HP group, the MHTs at 5 h and 3 d, and THT at 5 h after the first injection, and MHTs, and THTs at 4 and 24 h after the se-cond injection were significantly decreased in the HP group (P<0.01, P<0.05). 2) In the second part of the study, compared with the HP group, the MHTs at 4 and 24 h after the second injection and the THTs at 3 d after the first injection, 4 and 24 h after the second injection were significantly up-regulated in the EA group (P<0.01, P<0.05). The content of PAR 2 in the DRGs (L 4－L 6) was significantly higher in the HP group than in the sham-HP group (P<0.05), but considerably lower in the EA group than in the HP group (P<0.05). CONCLUSION: EA can suppress hyperalgesia priming in inflammatory pain rats which may be related to its effect in down-regulating PAR 2 level in the lumbar DRGs.

Effect of Electroacupuncture on Pain Reaction and Content of Proteinase-activated Receptors 2 in Dorsal Root Ganglion in Hyperalgesia Rats / 针刺研究

OBJECTIVE: To observe the effect of electroacupuncture (EA) on mechanical hyperalgesia threshold (MHTs) and thermal hyperalgesia threshold (THTs) and content of proteinase-activated receptors 2 (PAR 2) in dorsal root ganglia (DRG) in rats with inflammatory pain, so as to explore its peripheral mechanism underlying improvement of inflammatory pain. METHODS: The present study contains two parts. 1) In the first part, 27 male SD rats were randomized into sham hyperalgesic priming (sham-HP) group and real hyperalgesic priming (HP) group (n＝5 in the sham-HP group and n＝6 in the HP group for the test of MHTs, n＝8 in the two groups for the test of THTs). The sham-HP model was established by subcutaneous injection of normal saline into the left plantar part of the hind-paw, and the HP model established by subcutaneous injection of 1% carragenan (the first injection) into the same left hind paw, followed by injection of PGE2 (100 ng/25 μL, the second injection) into the dorsum pedis of the same hind paw 7 days after the first injection. The ipsilateral paw withdrawal latencies (MHTs and THTs) were detected before and 5 h, 3 d and 6 d after the first injection, 0.5, 4 and 24 h after the second injection. 2) In the second part, 64 male SD rats were randomly divided into sham-HP, HP, sham-EA and EA groups (n＝16 in each group). The sham-HP and HP models were made in the same way as the first part. Both"Zusanli"(ST 36)and "Kunlun"(BL 60) were punctured with filiform needles in the sham-EA group and also stimulated with EA: 2 Hz/100 Hz, 0.5－1.5 mA (0.5 mA increase per 10 min) for 30 min in the EA group, 1 time/d for 7 d. Both ipsilateral MHTs and THTs were observed at the same time-points of the first part and the PAR 2 protein content in the L 4－L 6 DRGs was assayed by ELISA 24 h after the second injection. RESULTS: 1) In the first part of the study, compared with the sham-HP group, the MHTs at 5 h and 3 d, and THT at 5 h after the first injection, and MHTs, and THTs at 4 and 24 h after the se-cond injection were significantly decreased in the HP group (P<0.01, P<0.05). 2) In the second part of the study, compared with the HP group, the MHTs at 4 and 24 h after the second injection and the THTs at 3 d after the first injection, 4 and 24 h after the second injection were significantly up-regulated in the EA group (P<0.01, P<0.05). The content of PAR 2 in the DRGs (L 4－L 6) was significantly higher in the HP group than in the sham-HP group (P<0.05), but considerably lower in the EA group than in the HP group (P<0.05). CONCLUSION: EA can suppress hyperalgesia priming in inflammatory pain rats which may be related to its effect in down-regulating PAR 2 level in the lumbar DRGs.

Phytochemical screening and analgesic profile of the lyophilized aqueous extract obtained from Chrysobalanus icaco leaves in experimental protocols.

CONTEXT: Chrysobalanus icaco L. (Chrysobalanaceae) has been used for the treatment of abdominal pain and cramps. OBJECTIVE: Assess the chemical and pharmacological profile of the lyophilized aqueous extract from C. icaco leaves (AEC). MATERIALS AND METHODS: Chromatographic methods were used to assess compounds from AEC. Mice were treated with vehicle (control group) or AEC (100, 200 or 400 mg/kg, p.o.) (group with 7-8 mice) and the analgesic profile was assessed employing the acetic acid-induced writhing, formalin, hot plate tests and hyperalgesia induced by carrageenan (CG) or tumour necrosis factor-alpha. The animal motor performance was assessed using rota-rod and grip strength tests. RESULTS: The chromatographic profile of AEC demonstrated the presence of terpenoid compounds. The acute pretreatment with AEC, at all doses, produced a significant (p < 0.01) inhibition of painful bahaviour (11.4 ± 3.6; 10.3 ± 2.8; 11.3 ± 2.2) when compared to the control group (24.7 ± 4.7) in acetic acid-induced writhing test. In the formalin test, AEC were effective in the second phase (p < 0.01) (57.2 ± 10.3; 56.3 ± 9.2; 54.7 ± 8.9) when compared to control group (121.9 ± 18.5). No response was observed in the hot plate test. The higher dose of AEC produced a significant (p < 0.01 or p < 0.05) inhibitory effect on the mechanical hyperalgesia test. AEC did not affect the motor performance of the mice. DISCUSSION: The terpenoids from AEC are known for its analgesic and anti-inflammatory properties. So, these results corroborate the experiments using the AEC in inflammatory pain protocols. CONCLUSION: Our results suggest that AEC act against inflammatory pain.

Nauclea latifolia Smith (Rubiaceae) exerts antinociceptive effects in neuropathic pain induced by chronic constriction injury of the sciatic nerve.

ETHNOPHARMACOLOGICAL RELEVANCE: The roots of Nauclea latifolia Smith (Rubiaceae) popularly known as "koumkouma" is used in traditional Cameroonian medicine as neuropathic pain remedy and for the treatment of headache, inflammatory pain and convulsion. This study was conducted to evaluate the antinociceptive effects of the alkaloid fraction isolated from Nauclea latifolia in neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve in rat. MATERIALS AND METHODS: Bioactive-guided fractionation of the root extracts of Nauclea latifolia using the Von Frey in a rat model of neuropathic pain (Benett model), afforded a potent anti-hyperalgesic fraction IV. Further fractionation of this fraction was performed by high-performance liquid chromatography (HPLC), yielded eight sub-fractions (F1-F8) which were tested for antinociceptive effects. The alkaloid fraction (F3) collected by HPLC, exhibited potent antinociceptive effects, and the anti-allodynic and anti-hyperalgesic effects of this fraction (8, 16, 40 and 80 mg/kg) were determined using the von Frey and acetone tests respectively in a rat model of neuropathic pain. Rota-rod performance and catalepsy tests were used for the assessment of motor coordination. RESULTS: The alkaloid fraction (80 mg/kg) administered intraperitoneally induced a completely decreased hyperalgesia 90 min post-dosing. In the acetone test, the Nauclea latifolia fraction at 80mg/kg showed its maximal anti-allodynic effects 120 min post-injection. The areas under the curve (AUC) of the anti-allodynic or anti-hyperalgesic effects produced by the alkaloid fraction at 80 mg/kg were significantly (p<0.001) greater than the AUC of effects produced by vehicle in CCI rats. The alkaloid fraction did not exhibit any significant effects on the spontaneous locomotor activity of the mice in rota-rod performance and no sign of catalepsy was observed. CONCLUSION: The analysis of the effects, expressed as the time course of AUC, supports the traditional use of Nauclea latifolia in neuropathic pain therapy. The pharmacological and chemical studies are continuing in order to characterize the mechanism(s) responsible for this anti-hyperalgesic and anti-allodynic action and also to identify the active substances present in the roots extracts of Nauclea latifolia.