Aleksander Roberto Zampronio

Involvement of bradykinin, cytokines, sympathetic amines and prostaglandins in formalin‐induced orofacial nociception in rats

This study characterises some of the mechanisms and mediators involved in the orofacial nociception triggered by injection of formalin into the upper lip of the rat, by assessing the influence of various treatments on behavioural nociceptive responses (duration of facial rubbing) elicited either by a low subthreshold (i.e. non‐nociceptive; 0.63%) or a higher concentration of the algogen (2.5%). The kininase II inhibitor captopril (5 mg kg−1, s.c.) and prostaglandin(PG) E2 (100 ng lip−1) potentiated both phases of the response to 0.63% formalin, whereas tumour necrosis factor (TNFα; 5 pg lip−1), interleukin(IL)‐1β (0.5 pg lip−1), IL‐6 (2 ng lip−1) and IL‐8 (200 pg lip−1), or the indirectly acting sympathomimetic drug tyramine (200 μg lip−1), each augmented only the second phase of nociception. Conversely, both phases of nociception induced by 2.5% formalin were inhibited by the bradykinin (BK) B2 receptor antagonist HOE140 (5 μg lip−1) or the selective β1‐adrenoceptor antagonist atenolol (100 μg lip−1). However, the BK B1 receptor antagonist des‐Arg9‐Leu8‐BK (1 and 2 μg lip−1), antibody and/or antiserum against each of the cytokines, the adrenergic neurone blocker guanethidine (30 mg kg−1 day−1, s.c., for 3 days) and the cyclooxygenase(COX)‐2 inhibitor celecoxib (50 and 200 μg lip−1, s.c.; or 1 and 3 mg kg−1, i.p.) reduced only the second phase of the response. The nonselective COX inhibitor indomethacin and the 5‐lipoxygenase activating protein inhibitor MK886 did not change formalin‐induced nociception. Our results indicate that BK, TNF‐α, IL‐1β, IL‐6, IL‐8, sympathetic amines and PGs (but not leukotrienes) contribute significantly to formalin‐induced orofacial nociception in the rat and the response seems to be more susceptible to inhibition by B2 receptor antagonist and selective COX‐2 inhibitor than by B1 receptor antagonist or nonselective COX inhibitor.

Orofacial cold hyperalgesia due to infraorbital nerve constriction injury in rats: reversal by endothelin receptor antagonists but not non-steroidal anti-inflammatory drugs.

Abstract The susceptibility of changes in responsiveness to noxious cold stimulation of rats submitted to chronic constriction of the infraorbital nerve (CION) or carrageenan to drug inhibition was compared. Nocifensive responses were measured as total time rats engaged in bilateral facial grooming with both forepaws over the first 2 min following tetrafluoroethane spray application to the snout. Carrageenan (50 &mgr;g, s.c. into upper lip) caused short‐lived ipsilateral cold hyperalgesia (peak at 3 h: vehicle 8.4 ± 1.3, carrageenan 21.2 ± 3.0 s) which was markedly suppressed by i.p. indomethacin (4 mg/kg), celecoxib (10 mg/kg) or s.c. dexamethasone (0.5 mg/kg), endothelin ETA or ETB receptor antagonists (BQ‐123 and BQ‐788, respectively; 10 nmol/lip). CION caused ipsilateral cold hyperalgesia between Days 2 and 12, which peaked on Days 4 (sham 15.3 ± 1.8, CION 32.4 ± 5.3 s) to 6. Established peak CION‐induced cold hyperalgesia was unaffected by indomethacin and celecoxib, whereas dexamethasone, BQ‐123, BQ‐788, and i.v. injections of selective antagonists of ETA (atrasentan, 3–10 mg/kg) or ETB (A‐192621, 5–20 mg/kg) receptors caused significant inhibitions lasting 1–2.5 h (peaks ˜65–90%). Bosentan (dual ETA/ETB receptor antagonist, 10 mg/kg, i.v.) abolished CION‐induced cold hyperalgesia for up to 6 h. Thus, once established, CION‐induced orofacial hyperalgesia to cold stimuli appears to lack an inflammatory component, but is alleviated by endothelin ETA and/or ETB receptor antagonists. If this CION injury model bears predictive value to trigeminal neuralgia (i.e., paroxysmal orofacial pain triggered by various stimuli), endothelin receptors might constitute new targets for treatment of this disorder.

A comparative study of the antipyretic effects of indomethacin and dipyrone in rats

Abstract. Objective: Compare the antipyretic effects of dipyrone and indomethacin.¶Materials and methods: Fever was induced in rats by i.v. LPS or i.c.v. interleukins (IL), prostaglandins (PG), arachidonic acid (AA), pre-formed pyrogenic factor (PFPF), tumour necrosis factor-α (TNF-α) or corticotrophin releasing hormone (CRH). Dipyrone and indomethacin were administered i.p., arginine vasopressin V1-receptor antagonist, d(CH2)5 Tyr(Me)AVP, into the ventral septal area. Cyclooxygenase (COX-1/-2) blocking activity was assessed in transfected COS-7 cells. CRH release from isolated hypothalami was determined by ELISA.¶Results: Indomethacin or dipyrone reduced LPS, IL-1β, IL-6 or TNF-α induced fever and CRH release from rat hypothalamus. Only dipyrone inhibited IL-8, PFPF or PGF2α fever. Only indomethacin inhibited fever induced by AA or IL-1β plus AA. Neither antipyretic affected fever caused by PGE2 or CRH. d(CH2)5Tyr(Me)AVP only blocked antipyresis induced by indomethacin. Dipyrone at a very high concentration (10 mM) inhibited only COX-1, while indomethacin (0.1 μM) blocked COX-1 and COX-2 in COS-7 cells.¶Conclusion: The antipyretic effect of dipyrone differs from that of indomethacin in that it does not depend on AVP release or inhibition of PG synthesis.

Mechanisms operated by endothelin ETA and ETB receptors in the trigeminal ganglion contribute to orofacial thermal hyperalgesia induced by infraorbital nerve constriction in rats

Endothelins, acting through specific endothelin ET(A) and/or ET(B) receptors, participate in nociceptive processing in models of cancer, inflammatory and neuropathic pain. The present study investigated which cell types express endothelin receptors in the trigeminal ganglion, and the contribution of mechanisms mediated by endothelin ET(A) and ET(B) receptors to orofacial heat hyperalgesia induced by unilateral constriction of the infraorbital nerve (CION). Both receptor types were identified by immunohistochemistry in the trigeminal ganglion, ET(A) receptors on small-sized non-myelinated and myelinated A-fibers and ET(B) receptors on both satellite glial cells and small-sized non-myelinated neuronal cells. CION promoted ipsilateral orofacial heat hyperalgesia which lasted from Day 2 until Day 10 after surgery. Ongoing CION-induced heat hyperalgesia (on Day 4) was reduced transiently, but significantly, by systemic or local treatment with antagonists of endothelin ET(A) receptors (atrasentan, 10 mg/kg, i.v.; or BQ-123, 10 nmol/lip), endothelin ET(B) receptors (A-192621, 20 mg/kg, i.v.; or BQ-788, 10 nmol/ lip), or of both ET(A)/ET(B) receptors (bosentan, 10 mg/kg, i.v.; or BQ-123 plus BQ-788, each at 10 nmol/lip). On the other hand, CION-induced heat hyperalgesia was transiently abolished over the first 90 min following i.p. injection of morphine hydrochloride (2.5 mg/kg), but fully resistant to reversal by indomethacin (4 mg/kg, i.p.) or celecoxib (10 mg/kg, i.p.). Thus, heat hyperalgesia induced by CION is maintained, in part, by peripheral signaling mechanisms operated by ET(A) and ET(B) receptors. Endothelin receptors might represent promising therapeutic targets for the control of trigeminal neuropathic pain.

Endothelin ETB receptor antagonist reduces mechanical allodynia in rats with trigeminal neuropathic pain

Trigeminal neuropathic pain, which is associated with marked orofacial mechanical allodynia, is frequently refractory to currently available drugs. Because endothelins (ETs) can contribute to nociceptive changes in animal models of inflammatory, cancer, and diabetic neuropathic pain, the present study evaluated the influence of ETA and ETB receptor antagonists on orofacial mechanical allodynia in a rat model of trigeminal neuropathic pain. Unilateral constriction (C) of the infraorbital nerve (ION) caused pronounced and sustained bilateral mechanical allodynia, evaluated by application of von Frey hairs to the vibrissal pad. Mechanical allodynia on postoperative days 12–15 after nerve injury was abolished for up to 90 mins by subcutaneous administration of 2.5 mg/kg morphine, but was fully refractory to intravenous (iv) administration of 10 mg/kg of the dual ETA plus ETB or selective ETA receptor antagonists, bosentan and atrasentan, respectively. In sharp contrast, iv administration of 20 mg/kg of the selective ETB receptor antagonist, A-192621, caused a net 61 ± 15% reduction of mechanical threshold, lasting 2 hrs. Co-injection of atrasentan plus A-192621 did not modify ION injury-induced mechanical allodynia. Injection of 10 pmol ET-1 into the upper lip of naive rats caused ipsilateral mechanical allodynia lasting up to 5 hrs. Thus, ETB receptor–mediated mechanisms contribute to orofacial mechanical allodynia induced by CION injury, but, some-how, functional ETA receptors are required for expression of the antiallodynic effect of ETB receptor blockade.

Peripheral substance P and neurokinin-1 receptors have a role in inflammatory and neuropathic orofacial pain models

There is accumulating evidence that substance P released from peripheral sensory neurons participates in inflammatory and neuropathic pain. In this study it was investigated the ability of substance P to induce orofacial nociception and thermal and mechanical hyperalgesia, as well as the role of NK1 receptors on models of orofacial inflammatory and neuropathic pain. Substance P injected into the upper lip at 1, 10 and 100 μg/50 μL failed to induce nociceptive behavior. Also, substance P (0.1-10 μg/50 μL) injected into the upper lip did not evoke orofacial cold hyperalgesia and when injected at 1 μg/50 μL did not induce mechanical hyperalgesia. However, substance P at this latter dose induced orofacial heat hyperalgesia, which was reduced by the pre-treatment of rats with a non-peptide NK1 receptor antagonist (SR140333B, 3mg/kg). Systemic treatment with SR140333B (3 mg/kg) also reduced carrageenan-induced heat hyperalgesia, but did not exert any influence on carrageenan-induced cold hyperalgesia. Blockade of NK1 receptors with SR140333B also reduced by about 50% both phases of the formalin response evaluated in the orofacial region. Moreover, heat, but not cold or mechanical, hyperalgesia induced by constriction of the infraorbital nerve, a model of trigeminal neuropathic pain, was abolished by pretreatment with SR140333B. Considering that substance P was peripherally injected (i.e. upper lip) and the NK1 antagonist used lacks the ability to cross the blood-brain-barrier, our results demonstrate that the peripheral SP/NK1 system participates in the heat hyperalgesia associated with inflammation or nerve injury and in the persistent pain evoked by formalin in the orofacial region.

Importance of the vagus nerve for fever and neutrophil migration induced by intraperitoneal LPS injection.

Abstract:Objective: We investigated the importance of the vagus nerve in fever, neutrophil migration and neutrophilia simultaneously induced by intraperitoneal injection of endotoxin (lipopolysaccharide, LPS) and in terms of the production of pre-formed pyrogenic factor (PFPF) and of the fever induced by this factor. Methods: Naïve, sham-operated or subdiaphragmatically vagotomized male Wistar rats received either LPS (i.p. or i.pl.) or PFPF (i.v., i.c.v., i.p.). The number of neutrophils was evaluated in peritoneal or pleural fluid and in blood. Fever was monitored using a rectal probe. Results: In naïve animals, LPS (0.02–200 μg kg–1, i.p.) induced dose-related neutrophilia and fever while on neutrophil migration it resulted in a bell-shaped curve. Vagotomy reduced the peritoneal resident cell population (56%), fever (71%) and neutrophil migration (43%) but not the neutrophilia or neutrophil migration to the pleural cavity. Vagotomy did not affect the PFPF production or PFPF-induced fever. Conclusions: Vagus nerve integrity is important not only for fever but also for the neutrophil influx to the peritoneal cavity by controlling the number of resident cells in this cavity.

Kinin B1 and B2 receptors contribute to orofacial heat hyperalgesia induced by infraorbital nerve constriction injury in mice and rats

Mechanisms coupled to kinin B(1) and B(2) receptors have been implicated in sensory changes associated to various models of neuropathy. The current study aimed to investigate if kinins also participate in orofacial thermal hyperalgesia induced by constriction of the infraorbital nerve (CION), a model of trigeminal neuropathic pain which displays persistent hypersensitivity to orofacial sensory stimulation, in rats and mice. Male Swiss mice (30-35g) or Wistar rats (200-250g; n=6-10 per group in both cases) underwent CION or sham surgery and were submitted repeatedly to application of heat ( approximately 50 degrees C) to the ipsilateral or contralateral snout, delivered by a heat source placed 1cm from the vibrissal pad. Decreases in latency to display head withdrawal or vigorous snout flicking were considered indicative of heat hyperalgesia. CION caused long-lasting heat hyperalgesia which started on Day 2 after surgery in both species and lasted up to Day 17 in mice and Day 10 in rats. Administration of DALBK or HOE-140 (peptidic B(1) and B(2) receptor antagonists, respectively; each at 3nmol in 10microl) onto the exposed infraorbital nerve of mice at the moment of surgery delayed the development of the thermal hyperalgesia. Systemic treatment on Day 5 (mice) or Day 4 (rats) with Des-Arg(9), Leu(8)-Bradykinin (DALBK, B(1) receptor antagonist, 0.1-1micromol/kg, i.p.) or HOE-140 (B(2) receptor antagonist, 0.001-1micromol/kg, i.p.) transiently reduced heat hyperalgesia in both species. Due to the peptidic nature of DALBK and HOE-140, it is likely that their effects reported herein resulted from blockade of peripheral kinin receptors. Thus, mechanisms operated by kinin B(1) and B(2) receptors, contribute to orofacial heat hyperalgesia induced by CION in both mice and rats. Perhaps kinin B(1) and B(2) receptor antagonists might constitute effective preventive and curative treatments for orofacial thermal hyperalgesia induced by nerve injury.

Anti-inflammatory effect of crude extract and isolated compounds from Baccharis illinita DC in acute skin inflammation

UNLABELLED ETHNOPHARMACOLOGYCAL RELEVANCE: The tea from the leaves of Baccharis illinita DC (Asteraceae family) is commonly used by the population as anti-inflammatory (including topically), protective gastric and anti-infectious. However, no studies have been done with this species to confirm its topical anti-inflammatory action. AIM This study evaluated he topical effects of crude extract of leaves (CE) and its active constituents in 12-O-tetradecanoylphorbol acetate (TPA)-induced ear oedema. METHODOLOGY CE and compounds effects were tested in commonly used models of TPA-, arachidonic acid (AA)- and capsaicin-ear oedema. Polymorphonuclear (PMN) cell migration was evaluated by mieloperoxidase and analyzed histologically. RESULTS CE (0.1-1 mg/ear) caused a dose-related inhibition of TPA-induced ear oedema and PMN influx similarly to that produced by topical application of the steroidal anti-inflammatory drug dexamethasone. The active constituents of the AcOEt fraction kaurenoic acid, alpha-spinasterol, oleanolic acid and baurenol also inhibited TPA-induced ear edema. Histological analysis of the ear of CE-treated animals confirmed the reduction of edema and of PMN infiltration. Both CE and the nosteroidal anti-inflammatory drug indomethacin inhibited the AA-induced ear oedema, but did not change capsaicin-induced oedema. CONCLUSION These results indicate that the CE and the active constituents have a topical anti-inflammatory effect and the possible mechanisms for the pharmacological effects are discussed.

Subchronic effects of dipyrone on the fish species Rhamdia quelen

The use of the non-steroidal anti-inflammatory drugs such as dipyrone is so widespread that this drug and its metabolites have been detected in effluents and surface water. This study aimed to evaluate the potential toxic effects of dipyrone on the aquatic environment, using a native fish species, Rhamdia quelen. Fish were exposed to three concentrations of dipyrone, 0.5, 5 and 50 μg/L, in the water for 15 days, and hematological, biochemical, genetic and morphological biomarkers were evaluated. The glutathione S-transferase activity decreased in the highest concentration in relation to the control group. In addition, hematocrit, red blood cells and thrombocyte counts were decreased in all three exposed groups in relation to the control group. The comet assay showed DNA damage at the lowest concentration of dipyrone and significant kidney damage. Those results suggest that a constant exposure of aquatic organisms to dipyrone presents potential toxic effects.