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This study carried out to investigate the anti-inflammatory and antinociceptive effect of tropane alkaloid (EB7) isolated from E. bezerrae. It evaluated the toxicity and possible involvement of ion channels in the antinociceptive effect of EB7, as well as its anti-inflammatory effect in adult zebrafish (Zfa). Docking studies with EB7 and COX-1 and 2 were also performed. The tested doses of EB7 (4, 20 and 40â mg/kg) did not show any toxic effect on Zfa during the 96h of analysis (LD50>40â mg/kg). They did not produce any alteration in the locomotor behavior of the animals. Furthermore, EB7 showed promising pharmacological effects as it prevented the nociceptive behavior induced by hypertonic saline, capsaicin, formalin and acid saline. EB7 had its analgesic effect blocked by amiloride involving the neuromodulation of ASICs in Zfa. In evaluating the anti-inflammatory activity, the edema induced by κ-carrageenan 3.5 % was reduced by the dose of 40â mg/kg of EB7 observed after the fourth hour of analysis, indicating an effect similar to that of ibuprofen. Molecular docking results indicated that EB7 exhibited better affinity energy when compared to ibuprofen control against the two evaluated targets binding at different sites in the cocrystallized COX-1 and 2 inhibitors.
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Analgésicos , Simulación del Acoplamiento Molecular , Pez Cebra , Animales , Analgésicos/farmacología , Analgésicos/química , Analgésicos/aislamiento & purificación , Tropanos/farmacología , Tropanos/aislamiento & purificación , Tropanos/química , Edema/tratamiento farmacológico , Edema/inducido químicamente , Carragenina/farmacología , Ciclooxigenasa 2/metabolismo , Ciclooxigenasa 1/metabolismo , Bignoniaceae/química , Relación Dosis-Respuesta a Droga , Relación Estructura-Actividad , Alcaloides/farmacología , Alcaloides/aislamiento & purificación , Alcaloides/química , Canales Iónicos Sensibles al Ácido/metabolismo , Canales Iónicos Sensibles al Ácido/química , Antiinflamatorios no Esteroideos/farmacología , Antiinflamatorios no Esteroideos/química , Antiinflamatorios no Esteroideos/aislamiento & purificación , Antiinflamatorios/farmacología , Antiinflamatorios/química , Antiinflamatorios/aislamiento & purificación , Estructura MolecularRESUMEN
This is the first study to analyze the anti-inflammatory and antinociceptive effect of withanicandrin, isolated from Datura Ferox leaves, and the possible mechanism of action involved in adult zebrafish (ZFa). To this end, the animals were treated intraperitoneally (i. p.) with withanicandrin (4; 20 and 40â mg/kg; 20â µL) and subjected to locomotor activity and acute toxicity. Nociception tests were also carried out with chemical agents, in addition to tests to evaluate inflammatory processes induced by κ-Carrageenan 1.5 % and a Molecular Docking study. As a result, withanicandrin reduced nociceptive behavior by capsaicin at a dose of 40â mg/kg and by acid saline at doses of 4 and 40â mg/kg, through neuromodulation of TRPV1 channels and ASICs, identified through blocking the antinociceptive effect of withanicandrin by the antagonists capsazepine and naloxone. Furthermore, withanicandrin caused an anti-inflammatory effect through the reduction of abdominal edema, absence of leukocyte infiltrate in the liver tissue and reduction of ROS in thel liver tissue and presented better affinity energy compared to control morphine (TRPV1) and ibuprofen (COX-1 and COX-2).
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Analgésicos , Pez Cebra , Animales , Analgésicos/farmacología , Analgésicos/química , Analgésicos/aislamiento & purificación , Canales Iónicos Sensibles al Ácido/metabolismo , Simulación del Acoplamiento Molecular , Antiinflamatorios/farmacología , Antiinflamatorios/química , Antiinflamatorios/aislamiento & purificación , Carragenina , Relación Estructura-Actividad , Relación Dosis-Respuesta a Droga , Canales Catiónicos TRPV/antagonistas & inhibidores , Canales Catiónicos TRPV/metabolismo , Edema/tratamiento farmacológico , Edema/inducido químicamente , Hojas de la Planta/química , Estructura MolecularRESUMEN
OBJECTIVE AND DESIGN: Our aim was to determine an age-dependent role of Nav1.8 and ASIC3 in dorsal root ganglion (DRG) neurons in a rat pre-clinical model of long-term inflammatory pain. METHODS: We compared 6 and 24 months-old female Wistar rats after cutaneous inflammation. We used behavioral pain assessments over time, qPCR, quantitative immunohistochemistry, selective pharmacological manipulation, ELISA and in vitro treatment with cytokines. RESULTS: Older rats exhibited delayed recovery from mechanical allodynia and earlier onset of spontaneous pain than younger rats after inflammation. Moreover, the expression patterns of Nav1.8 and ASIC3 were time and age-dependent and ASIC3 levels remained elevated only in aged rats. In vivo, selective blockade of Nav1.8 with A803467 or of ASIC3 with APETx2 alleviated mechanical and cold allodynia and also spontaneous pain in both age groups with slightly different potency. Furthermore, in vitro IL-1ß up-regulated Nav1.8 expression in DRG neurons cultured from young but not old rats. We also found that while TNF-α up-regulated ASIC3 expression in both age groups, IL-6 and IL-1ß had this effect only on young and aged neurons, respectively. CONCLUSION: Inflammation-associated mechanical allodynia and spontaneous pain in the elderly can be more effectively treated by inhibiting ASIC3 than Nav1.8.
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Canales Iónicos Sensibles al Ácido , Hiperalgesia , Canal de Sodio Activado por Voltaje NAV1.8 , Dolor , Animales , Femenino , Ratas , Canales Iónicos Sensibles al Ácido/genética , Canales Iónicos Sensibles al Ácido/metabolismo , Canales Iónicos Sensibles al Ácido/farmacología , Analgésicos/uso terapéutico , Ganglios Espinales , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/metabolismo , Inflamación/metabolismo , Dolor/tratamiento farmacológico , Dolor/metabolismo , Ratas Sprague-Dawley , Ratas Wistar , Células Receptoras Sensoriales/metabolismo , Canal de Sodio Activado por Voltaje NAV1.8/metabolismoRESUMEN
The effects during healthy aging of the tetrodotoxin-resistant voltage-gated sodium channel 1.8 (Nav1.8), the acid-sensing ion channel-3 (ASIC3), the purinergic-receptor 2X3 (P2X3) and transient receptor potential of melastatin-8 (TRPM8) on responses to non-noxious stimuli are poorly understood. These effects will influence the transferability to geriatric subjects of findings obtained using young animals. To evaluate the involvement of these functional markers in mechanical and cold sensitivity to non-noxious stimuli and their underlying mechanisms, we used a combination of immunohistochemistry and quantitation of immunostaining in sub-populations of neurons of the dorsal root ganglia (DRG), behavioral tests, pharmacological interventions and Western-blot in healthy male Wistar rats from 3 to 24 months of age. We found significantly decreased sensitivity to mechanical and cold stimuli in geriatric rats. These behavioural alterations occurred simultaneously with differing changes in the expression of Nav1.8, ASIC3, P2X3 and TRPM8 in the DRG at different ages. Using pharmacological blockade in vivo we demonstrated the involvement of ASIC3 and P2X3 in normal mechanosensation and of Nav1.8 and ASIC3 in cold sensitivity. Geriatric rats also exhibited reductions in the number of A-like large neurons and in the proportion of peptidergic to non-peptidergic neurons. The changes in normal sensory physiology in geriatric rats we report here strongly support the inclusion of aged rodents as an important group in the design of pre-clinical studies evaluating pain treatments.
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Envejecimiento Saludable , Canales Catiónicos TRPM , Ratas , Masculino , Animales , Canales Iónicos Sensibles al Ácido/metabolismo , Ratas Sprague-Dawley , Ratas Wistar , Células Receptoras Sensoriales/metabolismo , Canales Catiónicos TRPM/metabolismoRESUMEN
Acid-sensing ion channels (ASICs) are sensitized to activation by inflammatory mediators such as the polyunsaturated fatty acid (PUFA) arachidonic acid (AA). Previous work has shown that AA can potentiate ASIC currents at subsaturating proton concentrations, but the structural mechanisms of this change in gating are not understood. Here we show that PUFAs cause multiple gating changes in ASIC3, including shifting the pH dependence of activation, slowing the rate of desensitization, and increasing the current even at a saturating pH. The impact on gating depends on the nature of both the head and tail of the lipid, with the head group structure primarily determining the magnitude of the effect on the channel. An N-acyl amino acid (NAAA), arachidonyl glycine (AG), is such a strong regulator that it can act as a ligand at neutral pH. Mutation of an arginine in the outer segment of TM1 (R64) eliminated the effect of docosahexaenoic acid (DHA) even at high concentrations, suggesting a potential interaction site for the lipid on the channel. Our results suggest a model in which PUFAs bind to ASICs via both their tail group and an electrostatic interaction between the negatively charged PUFA head group and the positively charged arginine side chain. These data provide the first look at the structural features of lipids that are important for modulating ASICs and suggest a potential binding site for PUFAs on the channel.
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Canales Iónicos Sensibles al Ácido , Arginina , Canales Iónicos Sensibles al Ácido/metabolismo , Concentración de Iones de Hidrógeno , Lípidos , Dominios ProteicosRESUMEN
Increase in proton concentration [H+] or decrease in local and global extracellular pH occurs in both physiological and pathological conditions. Acid-sensing ion channels (ASICs), belonging to the ENaC/Deg superfamily, play an important role in signal transduction as proton sensor. ASICs and in particular ASIC1a (one of the six ASICs subunits) which is permeable to Ca2+, are involved in many physiological processes including synaptic plasticity and neurodegenerative diseases. Activity-dependent long-term potentiation (LTP) is a major type of long-lasting synaptic plasticity in the CNS, associated with learning, memory, development, fear and persistent pain. Neurons in the anterior cingulate cortex (ACC) play critical roles in pain perception and chronic pain and express ASIC1a channels. During synaptic transmission, acidification of the synaptic cleft presumably due to the co-release of neurotransmitter and H+ from synaptic vesicles activates postsynaptic ASIC1a channels in ACC of mice. This generates ASIC1a synaptic currents that add to the glutamatergic excitatory postsynaptic currents (EPSCs). Here we report that modulators like histamine and corticosterone, acting through ASIC1a regulate synaptic plasticity, reducing the threshold for LTP induction of glutamatergic EPSCs. Our findings suggest a new role for ASIC1a mediating the neuromodulator action of histamine and corticosterone regulating specific forms of synaptic plasticity in the mouse ACC.
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Canales Iónicos Sensibles al Ácido , Potenciación a Largo Plazo , Canales Iónicos Sensibles al Ácido/metabolismo , Animales , Corticosterona , Giro del Cíngulo/metabolismo , Histamina , RatonesRESUMEN
Drugs used to treat pain are associated with adverse effects, increasing the search for new drugs as an alternative treatment for pain. Therefore, we evaluated the antinociceptive behavior and possible neuromodulation mechanisms of triterpene 3ß, 6ß, 16ß-trihydroxylup-20(29)-ene (CLF-1) isolated from Combretum leprosum leaves in zebrafish. Zebrafish (n = 6/group) were pretreated with CLF-1 (0.1 or 0.3 or 1.0 mg/mL; i.p.) and underwent nociception behavior tests. The antinociceptive effect of CFL-1 was tested for modulation by opioid (naloxone), nitrergic (L-NAME), nitric oxide and guanylate cyclase synthesis inhibitor (methylene blue), NMDA (Ketamine), TRPV1 (ruthenium red), TRPA1 (camphor), or ASIC (amiloride) antagonists. The corneal antinociceptive effect of CFL-1 was tested for modulation by TRPV1 (capsazepine). The effect of CFL-1 on zebrafish locomotor behavior was evaluated with the open field test. The acute toxicity study was conducted. CLF-1 reduced nociceptive behavior and corneal in zebrafish without mortalities and without altering the animals' locomotion. Thus, CFL-1 presenting pharmacological potential for the treatment of acute pain and corneal pain, and this effect is modulated by the opioids, nitrergic system, NMDA receptors and TRP and ASIC channels.
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Analgésicos/farmacología , Combretum/química , Locomoción/efectos de los fármacos , Nocicepción/efectos de los fármacos , Dolor/prevención & control , Triterpenos/farmacología , Canales Iónicos Sensibles al Ácido/metabolismo , Amilorida/farmacología , Analgésicos/aislamiento & purificación , Animales , Alcanfor/farmacología , Capsaicina/análogos & derivados , Capsaicina/farmacología , Relación Dosis-Respuesta a Droga , Femenino , Ketamina/farmacología , Locomoción/fisiología , Masculino , Azul de Metileno/farmacología , NG-Nitroarginina Metil Éster/farmacología , Naloxona/farmacología , Nocicepción/fisiología , Dolor/metabolismo , Dolor/fisiopatología , Dimensión del Dolor , Extractos Vegetales/química , Hojas de la Planta/química , Receptores de N-Metil-D-Aspartato/metabolismo , Rojo de Rutenio/farmacología , Canales Catiónicos TRPV/metabolismo , Triterpenos/aislamiento & purificación , Pez Cebra , Proteínas de Pez Cebra/metabolismoRESUMEN
Extracellular pH changes may constitute significant signals for neuronal communication. During synaptic transmission, changes in pH in the synaptic cleft take place. Its role in the regulation of presynaptic Ca2+ currents through multivesicular release in ribbon-type synapses is a proven phenomenon. In recent years, protons have been recognized as neurotransmitters that participate in neuronal communication in synapses of several regions of the CNS such as amygdala, nucleus accumbens, and brainstem. Protons are released by nerve stimulation and activate postsynaptic acid-sensing ion channels (ASICs). Several types of ASIC channels are expressed in the peripheral and central nervous system. The influx of Ca2+ through some subtypes of ASICs, as a result of synaptic transmission, agrees with the participation of ASICs in synaptic plasticity. Pharmacological and genetical inhibition of ASIC1a results in alterations in learning, memory, and phenomena like fear and cocaine-seeking behavior. The recognition of endogenous molecules, such as arachidonic acid, cytokines, histamine, spermine, lactate, and neuropeptides, capable of inhibiting or potentiating ASICs suggests the existence of mechanisms of synaptic modulation that have not yet been fully identified and that could be tuned by new emerging pharmacological compounds with potential therapeutic benefits.
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Canales Iónicos Sensibles al Ácido/metabolismo , Encéfalo/fisiología , Protones , Transmisión Sináptica/fisiología , Animales , HumanosRESUMEN
Neem fruit (Azadirachta indica A. Juss.) are popularly used to treat infections, diarrhea, fever, bronchitis, skin diseases, infected burns and hypertension. Although the antinociceptive and anti-inflammatory potential of A. indica has already been investigated in experimental models of pain and inflammation in mice, the current research is the first to report the evaluation of the capacity of A. indica fruit ethanolic extract (EtFrNeem) in acute pain attenuation using the adult zebrafish (Danio rerio) as an alternative model to the use in rodents. EtFrNeem was submitted to antioxidant action, preliminary chemical prospecting, FT-IR and determination of phenol and flavonoid content tests. Subsequently, EtFrNeem was tested for acute nociception and abdominal inflammation, locomotor activity, and acute toxicity in adult zebrafish. Possible neuromodulation mechanisms were also evaluated. EtFrNeem showed low antioxidant activity, but was shown to be rich in flavonoids. EtFrNeem showed no anti-inflammatory action, did not alter the locomotor system, and it was not toxic. However, EtFrNeem significantly reduced the nociceptive behavior induced by formalin, glutamate and acidic saline, when compared to the control group. These effects of EtFrNeem were significantly similar to those of morphine, used as a positive control. The antinociceptive effect of EtFrNeem was inhibited by naloxone, ketamine and amiloride. EtFrNeem has the pharmacological potential for acute pain treatment and this effect is modulated by the opioid system, NMDA receptors and ASICs channels. These results lead us to studies of isolation and characterization of EtFrNeem bioactive principles, using adult zebrafish as an experimental model.
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Analgésicos Opioides/farmacología , Analgésicos/farmacología , Azadirachta/química , Fármacos actuantes sobre Aminoácidos Excitadores/farmacología , Frutas/química , Meliaceae/química , Extractos Vegetales/farmacología , Canales Iónicos Sensibles al Ácido/metabolismo , Animales , Antioxidantes/metabolismo , Modelos Animales de Enfermedad , Etanol , Flavonoides/farmacología , Locomoción/efectos de los fármacos , Morfina/farmacología , Dolor/tratamiento farmacológico , Dolor/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Pez CebraRESUMEN
Arrabidaea brachypoda (DC) Bureau is a medicinal plant found in Brazil. Known as "cipó-una", it is popularly used as a natural therapeutic agent against pain and inflammation. This study evaluated the chemical composition and antinociceptive activity of the dichloromethane fraction from the roots of A. brachypoda (DEAB) and its mechanism of action. The chemical composition was characterized by high-performance liquid chromatography, and this fraction is composed only of dimeric flavonoids. The antinociceptive effect was evaluated in formalin and hot plate tests after oral administration (10-100 mg/kg) in male Swiss mice. We also investigated the involvement of TRPV1 (transient receptor potential vanilloid 1), TRPA1 (transient receptor potential ankyrin 1), TRPM8 (transient receptor potential melastatin 8), and ASIC (acid-sensing ion channel), as well as the opioidergic, glutamatergic, and supraspinal pathways. Moreover, the nociceptive response was reduced (30 mg/kg) in the early and late phase of the formalin test. DEAB activity appears to involve the opioid system, TRPM8, and ASIC receptors, clearly showing that the DEAB alleviates acute pain in mice and suggesting the involvement of the TRPM8 and ASIC receptors and the opioid system in acute pain relief.
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Canales Iónicos Sensibles al Ácido/metabolismo , Analgésicos/uso terapéutico , Bignoniaceae/química , Dolor/tratamiento farmacológico , Extractos Vegetales/uso terapéutico , Canales Catiónicos TRPM/metabolismo , Analgésicos/química , Analgésicos/aislamiento & purificación , Analgésicos/farmacología , Animales , Locomoción/efectos de los fármacos , Masculino , Ratones , Dolor/metabolismo , Fitoterapia , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Extractos Vegetales/farmacología , Raíces de Plantas/química , Plantas Medicinales/químicaRESUMEN
Acid-sensing ion channels (ASICs) are a family of proton-sensing channels that are voltage insensitive, cation selective (mostly permeable to Na+), and nonspecifically blocked by amiloride. Derived from 5 genes (ACCN1-5), 7 subunits have been identified, 1a, 1b, 2a, 2b, 3, 4, and 5, that are widely expressed in the peripheral and central nervous system as well as other tissues. Over the years, different studies have shown that activation of these channels is linked to various physiological and pathological processes, such as memory, learning, fear, anxiety, ischemia, and multiple sclerosis to name a few, so their potential as therapeutic targets is increasing. This review focuses on recent advances that have helped us to better understand the role played by ASICs in different pathologies related to neurodegenerative diseases, inflammatory processes, and pain.
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Canales Iónicos Sensibles al Ácido/metabolismo , Sistema Nervioso Central/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Amilorida/uso terapéutico , Animales , Sistema Nervioso Central/efectos de los fármacos , Humanos , Enfermedades Neurodegenerativas/tratamiento farmacológicoRESUMEN
Low-intensity phototherapy using light fonts, like light-emitting diode (LED), in the red to infrared spectrum is a promising alternative for the treatment of pain. However, the underlying mechanisms by which LED phototherapy reduces acute pain are not yet well understood. This study investigated the analgesic effect of multisource LED phototherapy on the acute nocifensive behavior of mice induced by thermal and chemical noxious stimuli. The involvement of central afferent C fibers sensitive to capsaicin in this effect was also investigated. Mice exposed to multisource LED (output power 234, 390, or 780 mW and power density 10.4, 17.3, and 34.6 mW/cm2, respectively, from 10 to 30 min of stimulation with a wavelength of 890 nm) showed rapid and significant reductions in formalin- and acetic acid-induced nocifensive behavior. This effect gradually reduced but remained significant for up to 7 h after LED treatment in the last model used. Moreover, LED (390 mW, 17.3 mW/cm2/20 min) irradiation also reduced nocifensive behavior in mice due to chemical [endogenous (i.e., glutamate, prostaglandins, and bradykinin) or exogenous (i.e., formalin, acetic acid, TRPs and ASIC agonist, and protein kinase A and C activators)] and thermal (hot plate test) stimuli. Finally, ablating central afferent C fibers abolished LED analgesia. These experimental results indicate that LED phototherapy reduces the acute painful behavior of animals caused by chemical and thermal stimuli and that LED analgesia depends on the integrity of central afferent C fibers sensitive to capsaicin. These findings provide new information regarding the underlying mechanism by which LED phototherapy reduces acute pain. Thus, LED phototherapy may be an important tool for the management of acute pain.
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Vías Aferentes/fisiología , Conducta Animal/efectos de los fármacos , Capsaicina/farmacología , Calor , Luz , Fototerapia , Ácido Acético , Canales Iónicos Sensibles al Ácido/metabolismo , Adenilil Ciclasas/metabolismo , Vías Aferentes/efectos de los fármacos , Analgesia , Animales , Edema/patología , Femenino , Formaldehído , Ratones , Proteína Quinasa C/metabolismo , Reflejo , Canales de Potencial de Receptor Transitorio/metabolismoRESUMEN
INTRODUCTION: During exercise, the sympathetic nervous system is activated and blood pressure and HR increase. In heart failure (HF), the muscle metaboreceptor contribution to sympathetic outflow is attenuated and the mechanoreceptor contribution is accentuated. Previous studies suggest that lactic acid stimulates acid-sensing channel subtype 3 (ASIC3), inducing a neurally mediated pressor response. Thus, we hypothesized that the pressor response to ASIC3 stimulation is smaller in HF rats because of attenuation in expression and function of ASIC3 in sensory nerves. METHODS: Lactic acid was injected into the arterial blood supply of the hind limb to stimulate ASIC3 in muscle afferent nerves and evoke muscle metaboreceptor response in control rats and HF rats. In addition, western blot analysis was used to examine expression of ASIC3 in dorsal root ganglion (DRG) and patch clamp to examine current response with ASIC3 activation. RESULTS: Lactic acid (4 µmol·kg) increased mean arterial pressure by 28 ± 5 mm Hg in controls (n = 6) but only by 16 ± 3 mm Hg (P < 0.05 vs control) in HF (n = 8). In addition, HF decreased the protein levels of ASIC3 in DRG (optical density, 1.03 ± 0.02 in control, vs 0.79 ± 0.03 in HF; P < 0.05; n = 6 in each group). The peak current amplitude of dorsal DRG neuron in response to ASIC3 stimulation is smaller in HF rats than that in control rats. CONCLUSIONS: Compared with those in controls, cardiovascular responses to lactic acid administered into the hind limb muscles are blunted in HF rats owing to attenuated ASIC3. This suggests that ASIC3 plays a role in engagement in the attenuated metaboreceptor component of the exercise pressor reflex in HF.
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Canales Iónicos Sensibles al Ácido/metabolismo , Insuficiencia Cardíaca/fisiopatología , Mecanorreceptores/metabolismo , Músculo Esquelético/metabolismo , Condicionamiento Físico Animal/fisiología , Animales , Presión Sanguínea , Ganglios Espinales/metabolismo , Insuficiencia Cardíaca/diagnóstico por imagen , Insuficiencia Cardíaca/metabolismo , Frecuencia Cardíaca , Ácido Láctico/metabolismo , Masculino , Factor de Crecimiento Nervioso/metabolismo , Ratas Sprague-Dawley , UltrasonografíaRESUMEN
BACKGROUND: In the present study we determined the role of transient receptor potential V1 channel (TRPV1) and acid-sensing ion channel 3 (ASIC3) in chronic nociception. METHODS: 1% formalin was used to produce long-lasting secondary allodynia and hyperalgesia in rats. Western blot was used to determine TRPV1 and ASIC3 expression in dorsal root ganglia. RESULTS: Peripheral ipsilateral, but not contralateral, pre-treatment (-10min) with the TRPV1 receptor antagonists capsazepine (0.03-0.3µM/paw) and A-784168 (0.01-1µM/paw) prevented 1% formalin-induced secondary mechanical allodynia and hyperalgesia in the ipsilateral and contralateral paws. Likewise, peripheral ipsilateral, but not contralateral, pre-treatment with the non-selective and selective ASIC3 blocker benzamil (0.1-10µM/paw) and APETx2 (0.02-2µM/paw), respectively, prevented 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. Peripheral ipsilateral post-treatment (day 6 after formalin injection) with capsazepine (0.03-0.3µM/paw) and A-784168 (0.01-1µM/paw) reversed 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. In addition, peripheral ipsilateral post-treatment with benzamil (0.1-10µM/paw) and APETx2 (0.02-2µM/paw), respectively, reversed 1% formalin-induced secondary mechanical allodynia and hyperalgesia in both paws. TRPV1 and ASIC3 proteins were expressed in dorsal root ganglion in normal conditions, and 1% formalin injection increased expression of both proteins in this location at 1 and 6 days compared to naive rats. CONCLUSIONS: Data suggest that TRPV1 and ASIC3 participate in the development and maintenance of long-lasting secondary allodynia and hyperalgesia induced by formalin in rats. The use of TRPV1 and ASIC3 antagonists by peripheral administration could prove useful to treat chronic pain.
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Canales Iónicos Sensibles al Ácido/metabolismo , Hiperalgesia/fisiopatología , Canales Catiónicos TRPV/metabolismo , Canales Iónicos Sensibles al Ácido/genética , Amilorida/administración & dosificación , Amilorida/análogos & derivados , Amilorida/farmacología , Animales , Western Blotting , Capsaicina/administración & dosificación , Capsaicina/análogos & derivados , Capsaicina/farmacología , Venenos de Cnidarios/administración & dosificación , Venenos de Cnidarios/farmacología , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Formaldehído/toxicidad , Ganglios Espinales/metabolismo , Hiperalgesia/inducido químicamente , Hiperalgesia/prevención & control , Piridinas/administración & dosificación , Piridinas/farmacología , Ratas , Sulfonas/administración & dosificación , Sulfonas/farmacología , Canales Catiónicos TRPV/genética , Factores de TiempoRESUMEN
BACKGROUND: Citronellyl acetate (CAT), a monoterpene product of the secondary metabolism of plants, has been shown in the literature to possess several different biological activities. However, no antinociceptive abilities have yet been discussed. Here, we used acute pain animal models to describe the antinociceptive action of CAT. METHODS: The acetic acid-induced writhing test and the paw-licking test, in which paw licking was induced by glutamate and formalin, were performed to evaluate the antinociceptive action of CAT and to determine the involvement of PKC, PKA, TRPV1, TRPA1, TRPM8 and ASIC in its antinociceptive mechanism. To do so, we induced paw-linking using agonists. RESULTS: CAT was administered intragastrically (25, 50, 75, 100 and 200 mg/kg), and the two higher doses caused antinociceptive effects in the acetic acid model; the highest dose reduced pain for 4h after it was administered (200 mg/kg). In the formalin test, two doses of CAT promoted antinociception in both the early and later phases of the test. The glutamate test showed that its receptors are involved in the antinociceptive mechanism of CAT. Pretreatment with CAT did not alter locomotor activity or motor coordination. In an investigation into the participation of TRP channels and ASICs in CAT's antinociceptive mechanism, we used capsaicin (2.2 µg/paw), cinnamaldehyde (10 mmol/paw), menthol (1.2 mmol/paw) and acidified saline (2% acetic acid, pH 1.98). The results showed that TRPV1, TRPM8 and ASIC, but not TRPA1, are involved in the antinociceptive mechanism. Finally, the involvement of PKC and PKA was also studied, and we showed that both play a role in the antinociceptive mechanism of CAT. CONCLUSION: The results of this work contribute information regarding the antinociceptive properties of CAT on acute pain and show that, at least in part, TRPV1, TRPM8, ASIC, glutamate receptors, PKC and PKA participate in CAT's antinociceptive mechanism.