RESUMO

In this study, a pharmacological approach, together with the paw pressure test, was used to investigate the role of dopamine and its receptors in the peripheral processing of the nociceptive response in mice. Initially, the administration of dopamine (5, 20, and 80 ng/paw) in the hind paw of male Swiss mice (30-40 g) promoted antinociceptive effects in a dose-dependent manner. This was considered a peripheral effect, as it did not produce changes in the nociceptive threshold of the contralateral paw. The D2, D3, and D4 dopamine receptor antagonists remoxipride (4 µg/paw), U99194 (16 µg/paw), and L-745,870 (16 µg/paw), respectively, reversed the dopamine-mediated antinociception in mice with PGE2-induced hyperalgesia. The D1 and D5 dopamine receptor antagonists SKF 83566 (2 µg/paw) and SCH 23390 (1.6 µg/paw), respectively, did not alter dopamine antinociception. In contrast, dopamine at higher doses (0.1, 1, and 10 µg/paw) caused hyperalgesia in the animals, and the D1 and D5 receptor antagonists reversed this pronociceptive effect (10 µg/paw), whereas the D2 receptor antagonist remoxipride did not. Our data suggest that dopamine has a dual effect that depends on the dose, as it causes peripheral antinociceptive effects at small doses via the activation of D2-like receptors and nociceptive effects at higher doses via the activation of D1-like receptors.

Assuntos

RESUMO

Kahweol is a compound derived from coffee with reported antinociceptive effects. Based on the few reports that exist in the literature regarding the mechanisms involved in kahweol-induced peripheral antinociceptive action, this study proposed to investigate the contribution of the endocannabinoid system to the peripheral antinociception induced in rats by kahweol. Hyperalgesia was induced by intraplantar injection of prostaglandin E2(PGE2) and was measured with the paw pressure test. Kahweol and the drugs to test the cannabinoid system were administered locally into the right hind paw. The endocannabinoids were purified by open-bed chromatography on silica and measured by LC-MS. Kahweol (80 µg/paw) induced peripheral antinociception against PGE2-induced hyperalgesia. This effect was reversed by the intraplantar injection of the CB1 cannabinoid receptor antagonist AM251 (20, 40, and 80 µg/paw), but not by the CB2 cannabinoid receptor antagonist AM630 (100 µg/paw). Treatment with the endocannabinoid reuptake inhibitor VDM11 (2.5 µg/paw) intensified the peripheral antinociceptive effect induced by low-dose kahweol (40 µg/paw). The monoacylglycerol lipase (MAGL) inhibitor, JZL184 (4 µg/paw), and the dual MAGL/fatty acid amide hydrolase (FAAH) inhibitor, MAFP (0.5 µg/paw), potentiated the peripheral antinociceptive effect of low-dose kahweol. Furthermore, kahweol increased the levels of the endocannabinoid anandamide, but not of the other endocannabinoid 2-arachidonoylglycerol nor of anandamide-related N-acylethanolamines, in the plantar surface of the rat paw. Our results suggested that kahweol induced peripheral antinociception via anandamide release and activation of CB1 cannabinoid receptors and this compound could be used to develop new drugs for pain relief.

Assuntos

RESUMO

Kahweol is a compound derived from coffee with reported antinociceptive effects. Based on the few reports that exist in the literature regarding the mechanisms involved in kahweol-induced peripheral antinociceptive action, this study proposed to investigate the contribution of the endocannabinoid system to the peripheral antinociception induced in rats by kahweol. Hyperalgesia was induced by intraplantar injection of prostaglandin E2(PGE2) and was measured with the paw pressure test. Kahweol and the drugs to test the cannabinoid system were administered locally into the right hind paw. The endocannabinoids were purified by open-bed chromatography on silica and measured by LC-MS. Kahweol (80 µg/paw) induced peripheral antinociception against PGE2-induced hyperalgesia. This effect was reversed by the intraplantar injection of the CB1 cannabinoid receptor antagonist AM251 (20, 40, and 80 μg/paw), but not by the CB2 cannabinoid receptor antagonist AM630 (100 μg/paw). Treatment with the endocannabinoid reuptake inhibitor VDM11 (2.5 μg/paw) intensified the peripheral antinociceptive effect induced by low-dose kahweol (40 μg/paw). The monoacylglycerol lipase (MAGL) inhibitor, JZL184 (4 μg/paw), and the dual MAGL/fatty acid amide hydrolase (FAAH) inhibitor, MAFP (0.5 μg/paw), potentiated the peripheral antinociceptive effect of low-dose kahweol. Furthermore, kahweol increased the levels of the endocannabinoid anandamide, but not of the other endocannabinoid 2-arachidonoylglycerol nor of anandamide-related N-acylethanolamines, in the plantar surface of the rat paw. Our results suggested that kahweol induced peripheral antinociception via anandamide release and activation of CB1 cannabinoid receptors and this compound could be used to develop new drugs for pain relief.

RESUMO

Dipyrone (metamizole) is well-known for its powerful effect with central and peripheral activity. This meta-analysis involved articles published between 1973 and 2021, revealing that Brazil is the country which most published scientific articles relating the use of dipyrone in dogs, and this drug is widely recommended as an analgesic to control pain in cases of postoperative and cancer. Dipyrone is one of the favorite drugs used in small animal clinic in Brazil, and 12 commercial brands are available to use in dogs at doses among 25 to 50mg/kg for oral, intravenous and intramuscular administration. The effects of dipyrone may be potentiated when used in combination with other analgesic agents such as tramadol. In several studies, the occurrence of vomiting has been observed as an adverse effect, especially when the drug is used during surgical procedures, but metamizole has presented a low potential to cause gastric ulceration. The meta-analysis study of the use of dipyrone in dogs shows the clinical importance of this drug in Brazil, being an effective and safe medication, as long as it is used in the indicated dose of 25 mg/kg.

A dipirona (metamizol) é bem conhecida por seu poderoso efeito com atividade central e periférica. Esta meta-nálise envolveu estudos publicados entre os anos de 1973 a 2021, revelando que o Brasil é o país que mais publicou artigos científicos envolvendo o uso de dipirona em cães, sendo este fármaco amplamente recomendado como analgésico para controlar a dor em casos de câncer e dor pós-operatória. É um dos medicamentos preferidos da clínica médica de pequenos animais no Brasil. 12 marcas comerciais estão disponíveis para uso em cães em doses que variam de 25 a 50g para administração oral, intravenosa e intramuscular. Os efeitos da dipirona podem ser potencializados quando usada em combinação com outros analgésicos, como o tramadol. Em vários estudos, a ocorrência de vômito tem sido observada como efeito adverso, principalmente quando o medicamento é usado durante procedimentos cirúrgicos, mas tem baixo potencial para causar ulceração gástrica. O estudo de meta-análise do uso de dipirona em cães evidencia a importância do uso clínico deste fármaco no Brasil, sendo um medicamento eficaz e seguro para cães, desde que utilizada na dose indicada de 25 mg / kg.

Assuntos

RESUMO

Dipyrone (metamizole) is well-known for its powerful effect with central and peripheral activity. This meta-analysis involved articles published between 1973 and 2021, revealing that Brazil is the country which most published scientific articles relating the use of dipyrone in dogs, and this drug is widely recommended as an analgesic to control pain in cases of postoperative and cancer. Dipyrone is one of the favorite drugs used in small animal clinic in Brazil, and 12 commercial brands are available to use in dogs at doses among 25 to 50mg/kg for oral, intravenous and intramuscular administration. The effects of dipyrone may be potentiated when used in combination with other analgesic agents such as tramadol. In several studies, the occurrence of vomiting has been observed as an adverse effect, especially when the drug is used during surgical procedures, but metamizole has presented a low potential to cause gastric ulceration. The meta-analysis study of the use of dipyrone in dogs shows the clinical importance of this drug in Brazil, being an effective and safe medication, as long as it is used in the indicated dose of 25 mg/kg.

RESUMO

Dipyrone (metamizole) is well-known for its powerful effect with central and peripheral activity. This meta-analysis involved articles published between 1973 and 2021, revealing that Brazil is the country which most published scientific articles relating the use of dipyrone in dogs, and this drug is widely recommended as an analgesic to control pain in cases of postoperative and cancer. Dipyrone is one of the favorite drugs used in small animal clinic in Brazil, and 12 commercial brands are available to use in dogs at doses among 25 to 50mg/kg for oral, intravenous and intramuscular administration. The effects of dipyrone may be potentiated when used in combination with other analgesic agents such as tramadol. In several studies, the occurrence of vomiting has been observed as an adverse effect, especially when the drug is used during surgical procedures, but metamizole has presented a low potential to cause gastric ulceration. The meta-analysis study of the use of dipyrone in dogs shows the clinical importance of this drug in Brazil, being an effective and safe medication, as long as it is used in the indicated dose of 25 mg/kg.(AU)

A dipirona (metamizol) é bem conhecida por seu poderoso efeito com atividade central e periférica. Esta meta-nálise envolveu estudos publicados entre os anos de 1973 a 2021, revelando que o Brasil é o país que mais publicou artigos científicos envolvendo o uso de dipirona em cães, sendo este fármaco amplamente recomendado como analgésico para controlar a dor em casos de câncer e dor pós-operatória. É um dos medicamentos preferidos da clínica médica de pequenos animais no Brasil. 12 marcas comerciais estão disponíveis para uso em cães em doses que variam de 25 a 50g para administração oral, intravenosa e intramuscular. Os efeitos da dipirona podem ser potencializados quando usada em combinação com outros analgésicos, como o tramadol. Em vários estudos, a ocorrência de vômito tem sido observada como efeito adverso, principalmente quando o medicamento é usado durante procedimentos cirúrgicos, mas tem baixo potencial para causar ulceração gástrica. O estudo de meta-análise do uso de dipirona em cães evidencia a importância do uso clínico deste fármaco no Brasil, sendo um medicamento eficaz e seguro para cães, desde que utilizada na dose indicada de 25 mg / kg.(AU)

Assuntos

RESUMO

BACKGROUND: and purpose: The peptide PnPP-19, derived from the spider toxin PnTx2-6 (renamed as δ-CNTX-Pn1c), potentiates erectile function by activating the nitrergic system. Since NO has been studied as an antinociceptive molecule and PnPP-19 is known to induce peripheral antinociception, we intended to evaluate whether PnPP-19 could induce peripheral antinociception through activation of this pathway. EXPERIMENTAL APPROACH: Nociceptive thresholds were measured by paw pressure test. PGE2 (2 µg/paw) was administered intraplantarly together with PnPP-19 and inhibitors/blockers of NOS, guanylyl cyclase and KATP channels. The nitrite concentration was accessed by Griess test. The expression and phosphorylation of eNOS and nNOS were determined by western blot. KEY RESULTS: PnPP-19 (5, 10 and 20 µg/paw) induced peripheral antinociception in rats. Administration of NOS inhibitor (L-NOarg), selective nNOS inhibitor (L-NPA), guanylyl cyclase inhibitor (ODQ) and the blocker of KATP (glibenclamide) partially inhibited the antinociceptive effect of PnPP-19 (10 µg/paw). Tissue nitrite concentration increased after PnPP-19 (10 µg/paw) administration. Expression of eNOS and nNOS remained the same in all tested groups, however the phosphorylation of nNOS Ser852 (inactivation site) increased and phosphorylation of eNOS Ser1177 (activation site) decreased after PGE2 injection. Administration of PnPP-19 reverted this PGE2-induced effect. CONCLUSIONS AND IMPLICATIONS: The peripheral antinociceptive effect induced by PnPP-19 is resulting from activation of NO-cGMP-KATP pathway. Activation of eNOS and nNOS might be required for such effect. Our results suggest PnPP-19 as a new drug candidate to treat pain and reinforce the importance of nNOS and eNOS activation, as well as endogenous NO release, for induction of peripheral antinociception.

Assuntos

RESUMO

BACKGROUND AND PURPOSE: The synthetic peptide PnPP-19 has been studied as a new drug candidate to treat erectile dysfunction. However, PnTx2-6, the spider toxin from which the peptide was designed, induces hyperalgesia. Therefore, we intended to investigate the role of PnPP-19 in the nociceptive pathway. EXPERIMENTAL APPROACH: Nociceptive thresholds were measured by paw pressure test. PnPP-19 was administered intraplantarly alone or with selective cannabinoid or opioid receptor antagonists. The hydrolysis of PnPP-19 by neutral endopeptidase (NEP) (EC 3.4.24.11), an enzyme that cleaves enkephalin, was monitored by HPLC and the cleavage sites were deduced by LC-MS. Inhibition by PnPP-19 and Leu-enkephalin of NEP enzyme activity was determined spectrofluorimetrically. KEY RESULTS: PnPP-19 (5, 10 and 20 µg per paw) induced peripheral antinociception in rats. Specific antagonists of µ opioid receptors (clocinnamox), δ opioid receptors (naltrindole) and CB1 receptors (AM251) partly inhibited the antinociceptive effect of PnPP-19. Inhibition of fatty acid amide hydrolase by MAFP or of anandamide uptake by VDM11 enhanced PnPP-19-induced antinociception. NEP cleaved PnPP-19 only after a long incubation, and Ki values of 35.6 ± 1.4 and 14.6 ± 0.44 µmol·L(-1) were determined for PnPP-19 and Leu-enkephalin respectively as inhibitors of NEP activity. CONCLUSIONS AND IMPLICATIONS: Antinociception induced by PnPP-19 appears to involve the inhibition of NEP and activation of CB1, µ and δ opioid receptors. Our data provide a greater understanding of the antinociceptive effects of PnPP-19. This peptide could be useful as a new antinociceptive drug candidate.

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RESUMO

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been used extensively to control inflammatory pain. Several peripheral antinociceptive mechanisms have been described, such as opioid system and NO/cGMP/KATP pathway activation. There is evidence that the cannabinoid system can also contribute to the in vivo pharmacological effects of ibuprofen and indomethacin. However, there is no evidence of the involvement of the endocannabinoid system in the peripheral antinociception induced by NSAIDs. Thus, the aim of this study was to investigate the participation of the endocannabinoid system in the peripheral antinociceptive effect of NSAIDs. All experiments were performed on male Wistar rats (160-200 g; N = 4 per group). Hyperalgesia was induced by a subcutaneous intraplantar (ipl) injection of prostaglandin E2 (PGE2, 2 μg/paw) in the rat’s hindpaw and measured by the paw pressure test 3 h after injection. The weight in grams required to elicit a nociceptive response, paw flexion, was determined as the nociceptive threshold. The hyperalgesia was calculated as the difference between the measurements made before and after PGE2, which induced hyperalgesia (mean = 83.3 ± 4.505 g). AM-251 (80 μg/paw) and AM-630 (100 μg/paw) were used as CB1 and CB2 cannabinoid receptor antagonists, respectively. Ipl injection of 40 μg dipyrone (mean = 5.825 ± 2.842 g), 20 μg diclofenac (mean = 4.825 ± 3.850 g) and 40 μg indomethacin (mean = 6.650 ± 3.611 g) elicited a local peripheral antinociceptive effect. This effect was not antagonized by ipl CB1 cannabinoid antagonist to dipyrone (mean = 5.00 ± 0.9815 g), diclofenac (mean = 2.50 ± 0.8337 g) and indomethacin (mean = 6.650 ± 4.069 g) or CB2 cannabinoid antagonist to dipyrone (mean = 1.050 ± 6.436 g), diclofenac (mean = 6.675 ± 1.368 g) and indomethacin (mean = 2.85 ± 5.01 g). Thus, cannabinoid receptors do not seem to be involved in the peripheral antinociceptive mechanism of the NSAIDs dipyrone, diclofenac and indomethacin.

Assuntos

RESUMO

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been used extensively to control inflammatory pain. Several peripheral antinociceptive mechanisms have been described, such as opioid system and NO/cGMP/KATP pathway activation. There is evidence that the cannabinoid system can also contribute to the in vivo pharmacological effects of ibuprofen and indomethacin. However, there is no evidence of the involvement of the endocannabinoid system in the peripheral antinociception induced by NSAIDs. Thus, the aim of this study was to investigate the participation of the endocannabinoid system in the peripheral antinociceptive effect of NSAIDs. All experiments were performed on male Wistar rats (160-200 g; N = 4 per group). Hyperalgesia was induced by a subcutaneous intraplantar (ipl) injection of prostaglandin E2 (PGE2, 2 µg/paw) in the rat's hindpaw and measured by the paw pressure test 3 h after injection. The weight in grams required to elicit a nociceptive response, paw flexion, was determined as the nociceptive threshold. The hyperalgesia was calculated as the difference between the measurements made before and after PGE2, which induced hyperalgesia (mean = 83.3 ± 4.505 g). AM-251 (80 µg/paw) and AM-630 (100 µg/paw) were used as CB1 and CB2 cannabinoid receptor antagonists, respectively. Ipl injection of 40 µg dipyrone (mean = 5.825 ± 2.842 g), 20 µg diclofenac (mean = 4.825 ± 3.850 g) and 40 µg indomethacin (mean = 6.650 ± 3.611 g) elicited a local peripheral antinociceptive effect. This effect was not antagonized by ipl CB1 cannabinoid antagonist to dipyrone (mean = 5.00 ± 0.9815 g), diclofenac (mean = 2.50 ± 0.8337 g) and indomethacin (mean = 6.650 ± 4.069 g) or CB2 cannabinoid antagonist to dipyrone (mean = 1.050 ± 6.436 g), diclofenac (mean = 6.675 ± 1.368 g) and indomethacin (mean = 2.85 ± 5.01 g). Thus, cannabinoid receptors do not seem to be involved in the peripheral antinociceptive mechanism of the NSAIDs dipyrone, diclofenac and indomethacin.

Assuntos