RESUMO

OBJECTIVE: The aim of this study was to evaluate the antinociceptive activity of the methanol extract of Tabebuia hypoleuca stems (THME). MATERIALS AND METHODS: The animals were divided into 5 groups of 8 mice for each test (negative controls, positive controls, and 3 groups treated with THME at doses of 150, 300, and 500 mg/kg, p.o.). The antinociceptive effect of THME was evaluated using the writhing, formalin, tail flick, and hot plate models in mice. RESULTS: In the writhing test, THME (150, 300, and 500 mg/kg) produced significantly (p < 0.001) fewer writhes induced by acetic acid than in the control group. In the formalin test, the licking time for THME at doses of 300 and 500 mg/kg was significantly shorter (p < 0.001) compared to the control group in the first phase of the formalin test, whereas in the second phase only the dose of 500 mg/kg showed an antinociceptive effect. In addition, THME at doses of 300 and 500 mg/kg significantly increased the latency time in the tail flick test (p < 0.05 and p < 0.001, respectively) and in the hot plate test (p < 0.01 and p < 0.001, respectively) compared to the control group. CONCLUSIONS: These results show that THME had antinociceptive activity using several models of nociception, and they suggest that the effect is mediated by the participation of both peripheral and central antinociceptive mechanisms.

Assuntos

RESUMO

ABSTRACT: he Lantana camara L. belongs to the family Verbenaceae, which contains several active compounds in leaves and roots and which are reported to have medicinal and insecticidal properties. Studies of plants within the same family show the existence of anti-inflammatory activity in paw edema induced by carrageenan, serotonin and histamine and analgesic activity in the acetic acid writhing and tail-flick tests. The present study investigated whether the L. camara extract (ACE) also exerts these effects. The ACE toxicity was studied in male mice, and the percentage of mortality recorded 7 days after treatment was assessed. The ACE was evaluated as an antinociceptive agent in the hot plate, tail-flick and acetic acid writhing tests at a nontoxic dose of 1.0 g/Kg. The results showed that 1.5 g/Kg of ACE was not able to cause death, and doses of 3.0 and 4.0 g/Kg caused 50% and 60% death, respectively, in male mice. In all of the antinociceptive tests, 1 g/Kg of ACE markedly reduced responses to pain. Our findings suggest that ACE may have active anti-inflammatory and antinociceptive properties in much smaller doses than toxic.

RESUMO: Lantana camara L. pertence à família Verbenaceae, a qual contem muitos princípios ativos em suas folhas e raízes com propriedade medicinais e inseticidas. Estudos com plantas da mesma família mostram a existência de propriedades antinflamatórias no modelo de edema de pata induzido pela carragenina, serotonina e histamina, além da atividade analgésica nos testes de contorção induzida pelo ácido acético e da retirada da cauda por estímulo térmico. O presente trabalho investigou os efeitos tóxicos e antinociceptivos do extrato de L. camara (ACE) em camundongos. Para tanto, investigou-se a porcentagem de mortes em 7 dias após a administração de diferentes doses do extrato. Avaliou-se também os efeitos antinociceptivos do ACE pelos testes da placa quente, estimulação térmica da cauda e contorções abdominais induzidas pelo ácido acético com a dose não-tóxica [1,0 g/Kg]. Os resultados mostraram que 1,5 g/Kg do ACE não causou mortalidade, enquanto que 3,0 e 4,0 g/Kg promoveram 50 e 60% de mortalidade, respectivamente. Em todos os testes antinociceptivos, a dose de 1,0 g/Kg do ACE reduziu a resposta à dor. Os presentes resultados indicam que o ACE apresenta propriedades antinflamatórias e analgésicas em doses muito menores que a tóxica.

Assuntos

RESUMO

The stimulation of the retrosplenial cortex (RSC) is antinociceptive in the rat tail-flick and formalin tests. The rat RSC is caudal to and send projections to the ipsilateral anterior cingulate cortex (ACC), which is also involved in pain processing. This study demonstrated that pre-treating the rostral (rACC), but not the caudal ACC with CoCl2 (1mM), or the rACC ablation increased the duration of the antinociceptive effect evoked by a 15-s period of electrical stimulation (AC, 60Hz, 20µA) of the RSC in the rat tail-flick. Injecting the GABA-A antagonist bicuculline (50ng/0.25µL), but not the GABA-B antagonist phaclofen (300ng/0.25µL) into the rACC also increased the duration of the stimulation-induced antinociception from the RSC. In contrast, the effects of rACC stimulation persisted after the injection of CoCl2 (1mM) into the RSC. The injection of CoCl2 into the rACC did not change the nociceptive behavior of rats during phase 1 of the formalin response but reduced licking response duration during phase 2. This effect was similar in sham or stimulated animals at the RSC. We conclude that the antinociceptive effect of stimulating the RSC in the rat tail-flick test is modulated by the rACC involving GABA-A receptors in this cortex. In contrast, the antinociceptive effect of stimulating the RSC in the formalin test does not involve the rACC.

Assuntos

RESUMO

AIMS: The anterior pretectal nucleus (APtN) and electroacupuncture (EA) activate descending mechanisms to modulate nociceptive inputs in the spinal dorsal horn. This study examines qualitatively whether mechanisms in the APtN participate in the EA-induced analgesia in rats. MAIN METHODS: The tail-flick test was utilized to examine the changes produced by non-selective antagonists of serotonergic (methysergide, 37 pg), muscarinic (atropine, 10 ng) and opioid (naloxone, 10 ng) receptors; selective antagonists against µ (CTOP, 6.4 µg), δ (ICI174,864, 6.9 µg) or κ (nor-BNI, 7.3 µg); 5HT1 (methiothepin, 0.47 µg), 5HT2 (ketanserin, 5.4 µg), or 5HT3 (MDL 72222, 15.7 µg); and GABAA (bicuculline, 150 ng) receptors injected into the dorsal (d) or ventral (v) APtN on the antinociception induced by a 20-min EA applied at 2- or 100-Hz frequency to the Zusanli and Sanyinjiao acupoints. KEY FINDINGS: The 2-Hz EA-induced analgesia was blocked by naloxone, CTOP or atropine, was less intense after bicuculline, was shorter after methysergide or methiothepin in dAPtN, and was less intense after methysergide, methiothepin and bicuculline in vAPtN. The 100-Hz EA-induced analgesia was less intense after methysergide, methiothepin and CTOP in vAPtN, and remained unchanged after injection of the antagonists into the dAPtN. SIGNIFICANCE: The 2-Hz EA-induced analgesia utilizes cholinergic muscarinic, µ-opioid, GABAA and 5-HT1 mechanisms in the dAPtN and µ-opioid and 5-HT1 mechanisms in the vAPtN, while 100-Hz EA-induced analgesia utilizes µ-opioid and 5-HT1 mechanisms in the vAPtN but does not utilize them in the dAPtN.

Assuntos

RESUMO

OBJECTIVE: The aim of this study was to evaluate the effects of treadmill training on nociceptive sensitivity and immunoreactivity to calcitonin gene-related peptide in the dorsal horn of the spinal cord of diabetic rats. METHODS: Male Wistar rats were divided into three groups: control, diabetic and trained diabetic. Treadmill training was performed for 8 weeks. The blood glucose concentrations and body weight were evaluated 48 h after diabetes induction and every 30 days thereafter. The nociceptive sensitivity was evaluated using the tail-flick apparatus. The animals were then transcardially perfused, and the spinal cords were post-fixed, cryoprotected and sectioned in a cryostat. Immunohistochemistry for calcitonin gene-related peptide analysis was performed on the dorsal horn of the spinal cord. RESULTS: The nociceptive sensitivity analysis revealed that, compared with the control and trained diabetic animals, the latency to tail deflection on the apparatus was longer for the diabetic animals. Optical densitometry demonstrated decreased calcitonin gene-related peptide immunoreactivity in the dorsal horn of the spinal cord in diabetic animals, which was reversed by treadmill training. CONCLUSION: We concluded that treadmill training can alleviate nociceptive hypoalgesia and reverse decreased calcitonin gene-related peptide immunoreactivity in the dorsal horn of the spinal cord of diabetic animals without pharmacological treatment.

Assuntos