Antinociceptive effects of methysergide in various pain models

Several studies have demonstrated that the nonselective opioid receptor antagonist naloxone produces a paradoxical antinociception in the formalin test. The opioid system is related to the serotonergic system for producing antinociception at the spinal level. Here we also asked whether systemic (i.p.) and intrathecal (i.t.) administrations of a nonselective serotonergic antagonist, methysergide, might produce paradoxical antinociception similar to naloxone in the mouse formalin test. A diluted formalin solution was injected into the mouse plantar region of the hind paw and the duration of licking responses was measured at periods of 0-5 min (1st phase) and 20-40 min (2nd phase) after formalin injection. Methysergide administered i.p. and i.t. showed an attenuated licking duration only in the 2nd phase. The effect observed in the 2nd phase was reversed in the 5,7-dihydroxytriptamine, but not N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine pretreated group of mice, suggesting that descending serotonergic, but not noradrenergic, systems are involved in the methysergide antinociception. To further investigate the mechanism by which methysergide inhibited the nociceptive behaviors induced by formalin, the antinociceptive effect of methysergide was also tested in substance P (i.t.) and excitatory amino acids (i.t.), such as glutamate, N-methyl-D-aspartic acid, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, and kainic acid, which are major components in the formalin-induced nociceptive transmission in the spinal cord pain models. The duration of nociceptive behaviors shown in these models was significantly shortened by i.p. and i.t. administration of methysergide. These results suggest that methysergide also produces a paradoxical antinociception in various pain models including the formalin test, similar to the results of naloxone.     

Antinociceptive effect of methyleugenol on formalin-induced hyperalgesia in mice

The effects of methyleugenol, an essential oil isolated from Asiasari radix, on antinociception were examined using the formalin test in mice. Oral administration of 10 mg/kg methyleugenol significantly decreased the duration of licking and biting behavior in the second phase without affecting that of the first phase, as did diclofenac, a non-steroidal anti-inflammatory drug. Methyleugenol also inhibited pain-related behaviors induced by intrathecal injection of N-methyl-d-aspartic acid (NMDA), while diclofenac did not affect these behaviors. These effects of methyleugenol were suppressed by bicuculline, a gamma-aminobutyric acid(A) (GABA(A)) antagonist. Muscimol, a GABA(A) agonist, displays the same action as methyleugenol with respect to the formalin test and NMDA-induced behaviors. Methyleugenol did not affect cyclooxygenase-1 and -2 activities. These results suggest that the antinociceptive effect of methyleugenol on the second phase of formalin-induced pain may be due to the inhibition of NMDA receptor-mediated hyperalgesia via GABA(A) receptors.     

Mechanisms involved in the antinociception caused by ethanolic extract obtained from the leaves of Melissa officinalis (lemon balm) in mice

The present study examined the antinociceptive effect of the ethanolic extract from Melissa officinalis L. and of the rosmarinic acid in chemical behavioral models of nociception and investigates some of the mechanisms underlying this effect. The extract (3-1000 mg/kg), given orally (p.o.) 1 h prior to testing, produced dose-dependent inhibition of acetic acid-induced visceral pain, with ID50 value of 241.9 mg/kg. In the formalin test, the extract (30-1000 mg/kg, p.o.) also caused significant inhibition of both, the early (neurogenic pain) and the late (inflammatory pain), phases of formalin-induced licking. The extract (10-1000 mg/kg, p.o.) also caused significant and dose-dependent inhibition of glutamate-induced pain, with ID50 value of 198.5 mg/kg. Furthermore, the rosmarinic acid (0.3-3 mg/kg), given p.o. 1 h prior, produced dose-related inhibition of glutamate-induced pain, with ID50 value of 2.64 mg/kg. The antinociception caused by the extract (100 mg/kg, p.o.) in the glutamate test was significantly attenuated by intraperitoneal (i.p.) treatment of mice with atropine (1 mg/kg), mecamylamine (2 mg/kg) or l-arginine (40 mg/kg). In contrast, the extract (100 mg/kg, p.o.) antinociception was not affected by i.p. treatment with naloxone (1 mg/kg) or d-arginine (40 mg/kg). It was also not associated with non-specific effects, such as muscle relaxation or sedation. Collectively, the present results suggest that the extract produced dose-related antinociception in several models of chemical pain through mechanisms that involved cholinergic systems (i.e. through muscarinic and nicotinic acetylcholine receptors) and the l-arginine-nitric oxide pathway. In addition, the rosmarinic acid contained in this plant appears to contribute for the antinociceptive property of the extract. Moreover, the antinociceptive action demonstrated in the present study supports, at least partly, the ethnomedical uses of this plant.     

L-NG-nitro arginine methyl ester exhibits antinociceptive activity in the mouse.

1. L-NG-nitro arginine methyl ester (L-NAME, 1-75 mg kg-1) administered intraperitoneally (i.p.) elicits dose-related antinociception in the mouse assessed by the formalin-induced paw licking procedure. Antinociceptive activity is still present 24 h after injection. L-NAME (75 mg kg-1, i.p.) is also antinociceptive in the acetic acid-induced abdominal constriction and hot plate procedures. 2. L-NAME additionally produces a dose-related inhibition of formalin-induced paw licking following intracerebroventricular (i.c.v., 0.1-100 microgram per mouse) and oral (p.o., 75-150 mg kg-1) administration. 3. L-Arginine (600 mg kg-1, i.p.) but not D-arginine (600 mg kg-1) or naloxone (5 mg kg-1) reverses the antinociceptive effect of L-NAME in the formalin test. 4. High doses of L-NAME (37.5-600 mg kg-1) but not D-NAME (75 mg kg-1) administered i.p. produce dose-related increases in blood pressure of the urethane-anaesthetized mouse whilst i.c.v. injected L-NAME (0.1 and 100 microgram per mouse) in inactive. 5. L-NAME (75 mg kg-1, i.p.) did not inhibit oedema formation in the formalin-injected mouse hindpaw. 6. L-NAME (75 mg kg-1) did not produce any overt behavioural changes in treated mice and failed to influence locomotor activity or the incidence of dipping, crossing, rearing or circling behaviour assessed by a modified 'head-dipping' board procedure. A high dose of L-NAME (600 mg kg-1) reduced dipping behaviour and locomotor activity suggesting a possible sedative effect.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence for the involvement of glutamatergic receptors in the antinociception caused in mice by the sesquiterpene drimanial

Drimanial, a new sesquiterpene isolated from the barks of the plant Drimys winteri (Winteraceae), given systemically, intraplantarly, or by spinal or supraspinal routes, produced pronounced antinociception against both phases of formalin-induced licking. The systemic injection of drimanial also inhibited, in a graded manner, the pain-related behaviours induced by intraplantar or intrathecal (i.t.) administration of glutamate. Moreover, drimanial also caused marked inhibition of the nociception induced by i.t. administration of a metabotropic glutamate agonist (1S,3R)-ACPD, without affecting nociceptive responses induced by ionotropic agonists (NMDA, kainate, AMPA) or by substance P. The antinociception caused by drimanial was not influenced by naloxone, nor did it interfere with the motor coordination of animals in the rota-rod test. Furthermore, drimanial caused graded inhibition of [(3)H]glutamate binding in cerebral cortical membranes from mice, with an IC(50) value of 4.39 micro M. Together, these results provide strong evidence indicating that the sesquiterpene drimanial produces antinociception in mice at peripheral, spinal and supraspinal sites. An interaction with metabotropic glutamate receptors seems to contribute to the mechanisms underlying its antinociceptive action.     

Antinociceptive properties of the ethanolic extract and of the triterpene 3beta,6beta,16beta-trihidroxilup-20(29)-ene obtained from the flowers of Combretum leprosum in mice

The present study examined the antinociceptive effects of the ethanolic extract (EE) and of the triterpene 3beta,6beta,16beta-trihidroxilup-20(29)-ene obtained from the flowers of Combretum leprosum in chemical and thermal behavioural models of pain in mice. The EE (10-1000 mg/kg) given orally (p.o.), 1 h prior to testing, produced dose-dependent inhibition of acetic acid-induced visceral pain, with mean ID50 value of 131.9 mg/kg. In the formalin test, the EE (10-300 mg/kg, p.o.) also caused significant inhibition of both the early (neurogenic pain) and the late (inflammatory pain) phases of formalin-induced licking, however, it was more potent and efficacious in relation to the late phase of the formalin test, with mean ID50 values for the neurogenic and the inflammatory phases of approximately 300 and 88.8 mg/kg, respectively. The EE (10-1000 mg/kg, p.o.) also caused significant and dose-dependent inhibition of capsaicin- and glutamate-induced pain, with mean ID50 values of 160.5 and 38.3 mg/kg, respectively. Furthermore, the triterpene 3beta,6beta,16beta-trihidroxilup-20(29)-ene (1-30 mg/kg), given p.o., 1 h prior to testing, also produced dose-related inhibition of glutamate-induced pain, with a mean ID50 value of 5.6 mg/kg. When assessed in a thermal model of pain, the EE (10-300 mg/kg, p.o.) and fentanyl (100 microg/kg, s.c.) caused a significant and marked increase in the latency response on the hot-plate test (50 degrees C). The antinociception caused by EE (100 mg/kg, p.o.) in the glutamate test was significantly attenuated by intraperitoneal (i.p.) treatment of mice with naloxone (opioid receptor antagonist, 1 mg/kg), pindolol (a 5-HT 1A/1B receptor/beta adrenoceptor antagonist, 1 mg/kg), WAY100635 (a 5-HT 1A receptor antagonist, 0.7 mg/kg) or ketanserin (a 5-HT 2A receptor antagonist, 0.3 mg/kg). In contrast, EE (100 mg/kg, p.o.) antinociception was affected neither by L-arginine (precursor of nitric oxide, 600 mg/kg) nor by ondansetron (a 5-HT3 receptor antagonist, 0.5 mg/kg) i.p. treatment. It was not associated with non-specific effects such as muscle relaxation or sedation. Together, these results indicate that EE produces dose-related antinociception in several models of chemical and thermal pain through mechanisms that involve an interaction with opioid and serotonergic (i.e., through 5-HT 1A/1B and 5-HT 2A receptors) systems.     

Pharmacological evidence for the activation of K(+) channels by diclofenac

The involvement of K(+) channels in the antinociceptive action of diclofenac was assessed in the formalin test. Local administration of diclofenac produced a dose-dependent antinociceptive effect due to a local action because drug administration in the contralateral paw was ineffective. Pretreatment of the injured paw with glibenclamide and tolbutamide (ATP-sensitive K(+) channel inhibitors), charybdotoxin and apamin (large- and small-conductance Ca(2+)-activated K(+) channel blockers, respectively), 4-aminopyridine or tetraethylammonium (voltage-dependent K(+) channel inhibitors) prevented diclofenac-induced antinociception. Given alone, K(+) channel inhibitors did not modify formalin-induced nociceptive behavior. Pinacidil (an ATP-sensitive K(+) channel opener) also produced antinociception which was blocked by glibenclamide. The peripheral antinociceptive effect of morphine (positive control) was blocked by glibenclamide and 4-aminopyridine but not by charybdotoxin or apamin. The results suggest that the peripheral antinociceptive effect of diclofenac may result from the activation of several types of K(+) channels, which may cause hyperpolarization of peripheral terminals of primary afferents.     

Possible participation of nitric oxide/cyclic guanosine monophosphate/protein kinase C/ATP-sensitive K(+) channels pathway in the systemic antinociception of flavokawin B

The possible mechanisms of action in the antinociceptive activity induced by systemic administration (intraperitoneal, i.p.) of flavokawin B (FKB) were analysed using chemical models of nociception in mice. It was demonstrated that i.p. administration of FKB to the mice at 0.3, 1.0, 3.0 and 10 mg/kg produced significant dose-related reduction in the number of abdominal constrictions. The antinociception induced by FKB in the acetic acid test was significantly attenuated by i.p. pre-treatment of mice with L-arginine, the substrate for nitric oxide synthase or glibenclamide, the ATP-sensitive K(+) channel inhibitor, but was enhanced by methylene blue, the non-specific guanylyl cyclase inhibitor. FKB also produced dose-dependent inhibition of licking response caused by intraplantar injection of phorbol 12-myristate 13-acetate, a protein kinase C activator (PKC). Together, these data indicate that the NO/cyclic guanosine monophosphate/PKC/ATP-sensitive K(+) channel pathway possibly participated in the antinociceptive action induced by FKB.     

Characterization of socio-psychological stress-induced antinociception in the formalin test in mice

The antinociceptive effect induced by exposure to socio-psychological (PSY) stress using a communication box was assessed by the formalin test in mice, compared with those by exposure to footshock (FS) stress and forced swimming (SW) stress. After the termination of stress exposure, whereas exposure to FS- and SW-stress resulted in the attenuation of the formalin-induced biphasic pain response over 15 min, no appreciable antinociceptive effect was found in the case of PSY stress. When exposure to PSY stress was started during the period of early or late phase of pain after the formalin injection, the antinociceptive effect was maintained for 5-15 min; however, further exposure to PSY stress was not effective for producing antinociception. In the tail-pinch test, likewise, exposure to PSY stress longer than 5 min rather decreased the intensity of antinociception. We conclude that PSY stress in this tonic pain paradigm produces antinociception, but further continuous exposure to the emotional stress caused mice to become recuperative even in such a fear-inducing situation.     

3-Methyl-5-hydroxy-5-trichloromethyl-1H-1-pyrazolcarboxyamide induces antinociception

The antinociceptive action of a novel pyrazole-derived compound, 3-methyl-5-hydroxy-5-trichloromethyl-1H-1-pyrazolcarboxyamide (MPCA) was evaluated using the formalin and tail-immersion tests in mice. Anti-inflammatory activity was assessed by paw plethysmometry in adult rats using the carrageenin-induced paw edema test. Subcutaneous administration of MPCA (22, 66, and 200 mg/kg) induced a dose-dependent decrease in the time spent licking during the neurogenic and inflammatory phases of the formalin test, and preadministration of naloxone (1 mg/kg, sc) did not prevent MPCA-induced (200 mg/kg, sc) antinociception. Naloxone decreased the spontaneous locomotor activity of mice, while MPCA had no effect on locomotion. In contrast, administration of the opioid antagonist caused a significant increase in the locomotor behavior of mice previously injected with MPCA. MPCA was devoid of antinociceptive action by the tail-immersion test and of anti-inflammatory activity. Moreover, MPCA had no effect on the motor performance of mice in the rotarod test. These results suggest that MPCA induces antinociception in the neurogenic and inflammatory phases of the formalin test, an effect that does not involve opioid receptors.     

Antinociceptive effect of amikacin and its interaction with morphine and naloxone.

Amikacin sulphate (30 mg kg(-1)) administered either intraperitoneally (i.p.) or subcutaneously (s.c.) produced antinociceptive effect in BALB/c mice in the acetic acid writhing test which is employed as an inflammatory pain model. The lack of difference between two routes with regard to antinociceptive potency was taken as evidence for the absence of a local effect. Amikacin sulphate-induced antinociception seems unlikely to be due to non-specific behaviour alteration, since this drug, at a dose range of 15-100 mg kg(-1)did not affect motor coordination of mice in rot-a-rod test. Morphine (1 mg kg(-1)) also caused antinociception when administered i.p. or s.c. but the effect was greater with the latter route. At the i.p. site; the concurrent use of amikacin and morphine produced more remarkable antinociception compared to their individual usages. Besides, naloxone (2 mg kg(-1)) significantly decreased antinociceptive effect of amikacin but itself also exerted antinociception. At present, we have no plausible explanation for these findings at the i.p. site.     

Ciproxifan在小鼠痛觉传导调节机制中的作用

目的:研究组胺H3受体拮抗剂ciproxifan(CPF)在小鼠痛觉传导调节过程中的作用及其机制.方法:用3种不同的小鼠痛觉模型(热板法、扭体法和福尔马林实验)观察CPF的镇痛作用.同时用特异性组胺脱羧酶(HDC)抑制药α-氟甲基组胺酸(α-FMH),观察组胺在CPF发挥镇痛效应过程中所起的作用.在福尔马林致痛模型中,还测定了小鼠脑、脊髓和血清中一氧化氮(NO)和前列腺素E2(PGE2)的含量.结果:热板实验中,CPF 1 mg%.皮下注射福尔马林能引起2个时相(Ⅰ相、Ⅱ相)的痛反应.这种由福尔马林引起的2个时相的痛反应均可明显被CPF 0.3, 1, 3 mg*kg-1抑制. 在3种致痛模型中,CPF的镇痛效应均可被α-FMH 50 mg*kg-1逆转.使用福尔马林后,小鼠脑和脊髓中NO和PGE2水平升高,而CPF能明显抑制这种升高作用,该抑制作用不被α-FMH所拮抗.但CPF对血清中NO和PGE2的浓度没有影响.结论:组胺H3受体拮抗药CPF对多种性质刺激引起的疼痛均有镇痛作用,对福尔马林引起的炎性疼痛和非炎性疼痛都有效.CPF的这种镇痛作用可能与其促进组胺释放有关;同时脑和脊髓中的NO和PGE2可能参与了CPF的镇痛作用.     

Chemical and Pharmacological Studies of Phyllanthus caroliniensis in Mice

The aim of this study was to isolate and characterize the constituents of the hydroalcoholic extract (HE) of the leaves, stems and roots from P. caroliniensis, and also to evaluate the preliminary antinociceptive action of the HE and purified compounds in mice. Phytosterols, quercetin, gallic acid ethyl ester and geraniin were identified in P. caroliniensis on the basis of ¹H and ¹³C NMR spectral data and by mixed co-TLC and co-HPLC injection with authentic samples. The HE of P. caroliniensis (10-100 mg kg^?1, i.p.) inhibited, in a dose-related manner, acetic acid-induced abdominal constrictions in mice, with a mean ID50 value of 23.7 mg kg^?1. In the formalin test, the HE given intraperitoneally (1-30 mg kg^?1) or orally (25-600 mg kg^?1) caused graded inhibitions of both the neurogenic (first phase) and the inflammatory response (late phase) of formalin-induced licking. The HE was 54-fold more effective in inhibiting the late phase than it was in inhibiting the first phase of the formalin test, with mean ID50 values of 3.6 and 196.4 mg kg^?1, respectively. The HE failed, however, to affect the oedematogenic response associated with the late phase of formalin-induced pain. In addition, the reference drug, aspirin, given intraperitoneally (1-100 mg kg^?1) or orally (100-600 mg kg^?1), caused significant inhibition of the late but not the first phase of the formalin test. Pharmacological analysis also revealed that quercetin, gallic acid ethyl ester and a semi-purified fraction of flavonoids (1-100 mg kg^?1, i.p.) exhibited graded and significant antinociception against acetic acid-induced abdominal constriction. The mean ID50 values (mg kg^?1) for these effects were: 18.8, 34.7 and 5.3, respectively. It is concluded that quercetin, gallic acid ethyl ester and some as yet unidentified flavonoids might account for the antinociceptive action reported for the HE of P. caroliniensis.     

Antinociceptive and anti-oedematogenic properties of astilbin, taxifolin and some related compounds

Astilbin (3-0-alpha-1-rhamnosyl-(2R,3R)-dihydroquercetin), the major constituent isolated from Hymeneae martiana and some derivatives obtained by structural modification, such as taxifolin and two related compounds, were evaluated as analgesics by using both writhing test and formalin test in mice. Their anti-oedematogenic actions were also analysed against paw oedema caused by carrageenan, dextran and bradykinin in rat. The results indicated that some compounds, such as taxifolin (2) and its tetramethylated derivative (4) exhibited potent and dose-dependent antinociceptive action against acetic acid-induced abdominal constriction when administered intraperitoneally or orally. They were more potent than acetylsalicylic acid and paracetamol (acetaminophen), two standard drugs used for comparison. Compounds 2 and 4 were also more potent than these drugs in attenuating to the second phase of the formalin-induced licking. Moreover, both compounds showed significant anti-oedematogenic effect, inhibiting the paw oedema formation induced by dextran. In contrast pentaacetylated taxifolin (3) was capable of inhibiting the paw oedema induced by bradykinin.     

Pharmacological evidence for the activation of Ca2+-activated K+ channels by meloxicam in the formalin test

The possible participation of K+ channels in the antinociceptive action of meloxicam was assessed in the 1% formalin test. Local peripheral administration of meloxicam produced a dose-dependent antinociception only during the second phase of the formalin test. K+ channel blockers alone did not modify formalin-induced nociceptive behavior. However, local peripheral pretreatment of the paw with charybdotoxin and apamin (large- and small-conductance Ca2+-activated K+ channel inhibitors, respectively), 4-aminopyridine and tetraethylammonium (non-selective voltage-dependent K+ channel inhibitors), but not glibenclamide or tolbutamide (ATP-sensitive K+ channel inhibitors), dose-dependently prevented meloxicam-induced antinociception. It is concluded that meloxicam could open large- and small-conductance Ca2+-activated K+ channels, but not ATP-sensitive K+ channels, in order to produce its peripheral antinociceptive effect in the formalin test. The participation of voltage-dependent K+ channels was also suggested, but since non-selective inhibitors were used the data await further confirmation.     

Additive interaction between peripheral and central mechanisms involved in the antinociceptive effect of diclofenac in the formalin test in rats

It has been proposed that the antinociception of systemic diclofenac is the outcome of peripheral and central actions. Hence, our purpose was to examine if systemic diclofenac is able to achieve effective concentrations at local and spinal sites and to characterize the interaction between its local and spinal actions. Pain was produced in the rat using the formalin test. Oral diclofenac (1-10 mg/kg) reduced formalin-induced pain. The antinociceptive effect of oral diclofenac (10 mg/kg) was abolished by local or spinal administration of either L-NAME (1-100 microg and 1-50 microg) or glibenclamide (12.5-100 microg and 25-75 microg). These results suggest that oral diclofenac achieves effective concentrations producing an antinociceptive effect involving participation of the NO-potassium channel pathway at both, the local and spinal levels. In an additional experimental series, diclofenac was administered either locally (25-200 mug) or spinally (12.5-100 mug), yielding an antinociceptive effect by both routes. Then, diclofenac was given simultaneously by these two routes in a fixed-ratio, and antinociception was assayed. Isobolographic analysis revealed an additive interaction between the local and spinal effects of diclofenac. Hence, our results provide evidence that the overall antinociceptive effect induced by systemic diclofenac is the outcome of central and peripheral mechanisms.     

Mechanisms involved in the antinociceptive effects of orally administered oleanolic acid in the mouse

The antinociceptive effects of oleanolic acid were examined in ICR mice. Oleanolic acid administered orally (1, 5 and 10 mg/kg) showed an antinociceptive effect in a dose-dependent manner as measured in the acetic acid-induced writhing test. In the time- course study, duration of antinociceptive action of oleanolic acid maintained at least for 60 min. In addition, the cumulative nociceptive response time for intraplantar formalin injection (2nd phase), intrathecal injection of substance P (0.7 μg) or glutamate (20 μg) was diminished by oleanolic acid. Intraperitoneal (i.p.) pretreatment with naloxone (opioid receptor antagonist) or methysergide (5-HT serotonergic receptor antagonist) attenuated antinociceptive effect induced by oleanolic acid in the writhing test. However, yohimbine (adrenergic receptor antagonist) did not affect antinociception induced by oleanolic acid. The results indicate that oleanolic acid shows an antinociceptive property in various pain models such as writhing, formalin, substance P and glutamate pain tests. Furthermore, this antinociceptive effect of oleanolic acid may be mediated by opioidergic and serotonergic receptors, but not adrenergic receptors.     

Probable activation of the opioid receptor-nitric oxide-cyclic GMP-K+ channels pathway by codeine

There is evidence that local peripheral administration of morphine produces antinociception through the activation of the nitric oxide (NO)-cyclic GMP-K(+) channels pathway. Therefore we evaluated the possible participation of this pathway in the antinociceptive action produced by codeine in the rat 5% formalin test. Local peripheral injection of codeine produced a dose-dependent antinociception during the first and second phases of the test. Local pretreatment of the paws with the NO synthase inhibitor N(G)-L-nitro-arginine methyl ester (L-NAME), the soluble guanylyl cyclase inhibitor methylene blue, the ATP-sensitive K(+) channel inhibitors glibenclamide and tolbutamide, the non-selective voltage-gated K(+) channel inhibitors 4-aminopyridine (4-AP) and tetraethylammonium (TEA) and the opioid receptor blocker naloxone prevented codeine-induced antinociception in both phases of the test. L-NAME, methylene blue, K(+) channel blockers and naloxone by themselves did not modify formalin-induced nociceptive behavior. Our data suggest that codeine could activate the opioid receptor-NO-cyclic GMP-K(+) channels pathway in order to produce its peripheral antinociceptive effect in the formalin test.     

在小鼠痛觉传导调节机制中的作用(英文)

目的 :研究组胺H3受体拮抗剂ciproxifan(CPF)在小鼠痛觉传导调节过程中的作用及其机制。方法 :用 3种不同的小鼠痛觉模型 (热板法、扭体法和福尔马林实验 )观察CPF的镇痛作用。同时用特异性组胺脱羧酶 (HDC)抑制药α 氟甲基组胺酸 (α FMH) ,观察组胺在CPF发挥镇痛效应过程中所起的作用。在福尔马林致痛模型中 ,还测定了小鼠脑、脊髓和血清中一氧化氮 (NO)和前列腺素E2(PGE2 )的含量。结果 :热板实验中 ,CPF 1mg·kg- 1和 3mg·kg- 1能明显延长小鼠的痛反应时间 ,其镇痛作用从用药后 2 0min开始 ,可持续 6 0min以上。扭体实验中 ,CPF 1mg·kg- 1可明显抑制小鼠的扭体次数 ,最高抑制率达 4 9.85 %。皮下注射福尔马林能引起 2个时相 (Ⅰ相、Ⅱ相 )的痛反应。这种由福尔马林引起的 2个时相的痛反应均可明显被CPF 0 .3,1,3mg·kg- 1抑制。在 3种致痛模型中 ,CPF的镇痛效应均可被α FMH 5 0mg·kg- 1逆转。使用福尔马林后 ,小鼠脑和脊髓中NO和PGE2 水平升高 ,而CPF能明显抑制这种升高作用 ,该抑制作用不被α FMH所拮抗。但CPF对血清中NO和PGE2 的浓度没有影响。结论 :组胺H3受体拮抗药CPF对多种性质刺激引起的疼痛均有镇痛作用 ,对福尔马林引起的炎性疼痛和非炎性疼痛都有效。CPF的这种镇痛作用可能与其促进?     

Antinociceptive effect of certain dihydroxy flavones in mice

Objective

This study was designed to evaluate the antinociceptive action of four dihydroxy flavone derivatives; 3,3′-dihydroxy flavone, 5,6-dihydroxy flavone, 3,7-dihydroxy flavone and 6,3′-dihydroxy flavone and to investigate the mechanisms involved.

Materials and methods

The antinociceptive effect of dihydroxy flavones was investigated in mice employing acetic acid induced abdominal constrictions, formalin-induced nociception, and hot plate assay procedures. The effects following pretreatment with naloxone, yohimbine, ondansetron, haloperidol, bicuculline and glibenclamide were also studied by acetic acid assay to reveal the involvement of opioid, adrenergic, tryptaminergic, dopaminergic, GABAergic or potassium channels respectively in the antinociceptive action of these compounds.

Results

Dihydroxy flavone derivatives significantly reduced the number of abdominal constrictions in acetic acid assay. The paw licking response time during both the early and late phases of formalin-induced nociception was reduced in a dose dependent manner by dihydroxy flavones treatment. A significant increase in reaction time was also evident in hot plate assay after dihydroxy flavones treatment.The antinociceptive effect of dihydroxy flavones in the acetic acid assay was significantly attenuated by pretreatment with either naloxone or bicuculline. However, pretreatment of animals with yohimbine, ondansetron, haloperidol, or glibenclamide did not alter the response.

Conclusion

All the four investigated dihydroxy flavones produced dose related antinociception through mechanisms that involve an interaction with opioid and GABAergic pathways.