Tail-pinch Test Research Articles

Suppression of hyperalgesia in streptozotocin-induced diabetic mice by a lipopolysaccharide from Pantoea agglomerans.

The ability of a lipopolysaccharide from Pantoea agglomerans (LPSp) to relieve hyperalgesia was examined by observing its inhibition of the decrease in the threshold for nociceptive perception, as determined by the tail-pinch test, in streptozotocin-induced diabetic mice. Subcutaneous injection of LPSp suppressed hyperalgesia in streptozotocin-induced diabetic mice and also exerted a therapeutic effect on hyperalgesia in these animals. The present data suggest that LPSp may be effective in relieving the pain associated with diabetic neuropathy.

Differential mediation of cold water swim stress-induced antinociception by δ-opioid receptor subtypes in diabetic mice

The involvement of δ-opioid receptor subtypes in cold water swim stress (CWSS)-induced antinociception in diabetic mice was compared with that in non-diabetic mice. Three-minute swim stress produced significant antinociception in both diabetic and non-diabetic mice as determined by the tail-pinch test. However, the extent of CWSS-induced antinociception in diabetic mice was significantly greater than that in non-diabetic mice. Pretreatment with naltriben, a selective δ 2-opioid receptor antagonist, significantly attenuated CWSS-induced antinociception in both non-diabetic and diabetic mice. In contrast, although 7-benzylidenenaltrexone, a selective δ 1-opioid receptor antagonist, significantly attenuated CWSS-induced antinociception in diabetic mice, it had no effect in non-diabetic mice. These results suggest that CWSS-induced antinociceotion in non-diabetic mice is mediated by δ 2-opioid receptors, whereas CWSS-induced antinociception in diabetic mice is mediated by both δ 1- and δ 2-opioid receptors. Furthermore, the enhanced CWSS-induced antinociception in diabetic mice may be due to the activation of δ 1-opioid receptors.

Periaqueductal gray matter stimulation-produced analgesia in diabetic rats

The effect of diabetes on periaqueductal gray matter (PAG) stimulation-produced analgesia (SPA) was examined in rats. PAG SPA was assessed using the tail-pinch test. PAG stimulation produced marked analgesia in both naive and diabetic rats. Furthermore, the degree of PAG SPA did not differ between naive and diabetic rats. PAG SPA was significantly attenuated by a low dose (0.5 mg/kg, s.c.) of naloxone in naive rats, but not in diabetic rats. However, a high dose (5 mg/kg, s.c.) of naloxone significantly and equally attenuated PAG SPA in both naive and diabetic rats. On the other hand, the analgesic potency of morphine (3 mg/kg, s.c.) was significantly reduced in diabetic rats as compared with naive rats. These results suggest that PAG SPA in diabetic rats may be mediated by different opioid receptor interactions as compared with naive rats.

Antagonism of U-50,488H-induced antinociception by ginseng total saponins is dependent on serotonergic mechanisms

Morphine-induced antinociception was prevented by pretreatment with ginseng total saponins in the tail-pinch and tail-flick tests carried out in mice. The antinociceptive effect of U-50,488H, a selective κ-opioid receptor agonist, was prevented by naloxone, a nonselective opioid receptor antagonist, in the tail-pinch but not in the tail-flick test. However, U-50,488H-induced antinociception was prevented by ginseng total saponins in the tail-flick but not in the tail-pinch test. These results indicate that nonopioid mechanisms are involved in the antagonism of U-50,488H-induced antinociception by ginseng total saponins. In addition, the antagonism of U-50,488H-induced antinociception in mice pretreated with ginseng total saponins was abolished by pretreatment with a serotonin precursor, 5-hydroxytryptophan, but not by a noradrenaline precursor, L-dihydroxyphenylalanine, in the tail-flick test. Therefore, it appears that the antagonism of U-50,488H-induced antinociception by ginseng total saponins is dependent on serotonergic mechanisms.

Central monoaminergic mechanisms in mice and analgesic activity of spiradoline mesylate, a selective κ-opioid receptor agonist

We assessed the roles of brain monoaminergic systems in the analgesic action of spiradoline, a novel κ-opioid agonist, behaviorally and biochemically by using noradrenaline (NE) and serotonin (5-HT) uptake inhibitors. Analgesic activity was evaluated by measuring latency time in the mouse tail-pinch test. Spiradoline at intramuscular doses of 0.3 mg/kg or more elicited a significant analgesic effect and the metabolism of both NE and 5-HT was significantly increased in brainstem and cortex. Pretreatment of the mice with imipramine, desipramine or clomipramine caused marked otentiation of spiradoline analgesia, whereas reserpine and phenoxybenzamine inhibited it. Morphine analgesia was enhanced by clomipramine but not by imipramine, desipramine or phenoxybenzamine. These results suggest that excitation of noradrenergic and serotonergic pathways in the brain appears to be involved in spiradoline analgesia, and that, as regards tail-pinch nociception, the κ-opioid agonist acts on the noradrenergic pathway more potently than morphine.

Streptozotocin-induced diabetes in mice reduces the nociceptive threshold, as recognized after application of noxious mechanical stimuli but not of thermal stimuli

We report herein that streptozotocin (STZ)-induced diabetes selectively alters the nociceptive threshold with respect to noxious mechanical stimuli. Mice were rendered diabetic by an injection of STZ (200 mg/kg, IV). In the tail-pinch test, the latency of the biting response to forceps was significantly decreased in animals with diabetes of 2 weeks and 8 weeks duration as compared to that in age-matched controls. However, the nociceptive threshold, as determined by the tail-flick test, was not significantly altered. The level of substance P in the spinal cord was significantly increased in mice that has been diabetic for 2 weeks, while, there was a significant decrease, as compared to control levels, in level of substance P in mice diabetic for 8 weeks. However, the level of somatostatin was not significantly altered in mice diabetic for either 2 weeks or 8 weeks. These data suggest that STZ-induced diabetes selectively alters a neuronal system that involves substance P but not somatostatin in the spinal cord.

An Attempted Reversal of Cocaine-Induced Analgesia by Dexamethasone

Analgesia produced by systemic cocaine (20 mg/kg intraperitoneally) was not attenuated by dexamethasone (0.25-2.5 mg/kg) in the formalin or tail pinch test in rats. The result suggests that the activation of the corticotropin releasing factor-adrenocorticotropin/beta-endorphin axis does not explain cocaine-induced analgesia.

Synthesis and Pharmacological Activity of Sulfate Conjugates at 6-Position of N-Substituted Normorphine Derivatives.

Three pairs of N-substituted normorphine derivatives and the sulfate conjugates at the 6-position were tested for the analgesic and antagonistic activities and the development of physical dependence in mice. The compounds examined were nalorphine, nalorphine-6-sulfate (N-6-S), N-cyclopropylmethylnormorphine (CPN), N-cyclopropylmethylnormorphine-6-sulfate (C-6-S), N-dimethylallylnormorphine (DMN) and N-dimethylallylnormorphine-6-sulfate (D-6-S). The latter two pairs were newly synthesized. The analgesic activity of C-6-S and D-6-S was equipotent to that of CPN and DMN by the acetic acid writhing test on the s.c. injection, and the activity of N-6-S was about 2 times more potent than that of nalorphine. The antagonistic activity of N-6-S, C-6-S and D-6-S to morphine analgesia was higher than that of the parent compounds by the tail pinch test on i.c.v. injection. A withdrawal sign was seen in mice treated chronically with CPN, C-6-S and N-6-S by challenge with naloxone, whereas the mice treated with DMN, D-6-S and nalorphine showed no such sign. The effect of sulfation at the 6-position on the development of physical dependence was not well associated with the effect on agonistic and antagonistic activities.

Attempted reversal of cocaine-induced antinociceptive effects with naloxone, an opioid antagonist

We attempted to reverse the behavioral and neuronal antinociceptive effects of cocaine with naloxone, an opioid antagonist. Cocaine (20 mg/kg i.p.) produced a strong analgesic effect in the formalin test and in the tail pinch test. These cocaine-induced analgesic effects could be reversed by naloxone at a very high dose (10 mg/kg) but not at a dose (1 mg/kg) which was sufficient to attenuate morphine (10 mg/kg)-induced analgesia. Naloxone alone at a dose of 10 mg/kg did not produce significant effects. In general, nociceptively evoked responses in medial thalamic neurons were suppressed by cocaine (20 mg/kg), and this suppression was attenuated by naloxone (10 mg/kg). The results suggest that opioid receptors which are not involved in mediating morphine-induced analgesia and which have a low sensitivity to naloxone are involved in cocaine-induced central analgesia.

Development of supersensitivity to substance P in the spinal cord of the streptozotocin-induced diabetic rats

To investigate the possible mechanisms involved in the alterations in sensitivity to pain in diabetic rats, we examined the influence of diabetes induced by streptozotocin (STZ) on the functions of the neuronal systems that contain substance P (SP) within the spinal cord. The threshold for pain perception as determined by a tail-pinch test was significantly reduced in diabetic rats. The levels of SP in the spinal cord from diabetic rats (116.9 ± 16.3 pmol/g tissue) were significantly lower than those from the control rats (190.2 ± 14.1 pmol/g tissue). Diabetic rats were found to have a significant increase in the number of binding sites for SP in dorsal spinal cord. The concentrations of binding sites in diabetic rats and in control rats were 102.1 ± 17.3 fmol/mg protein and 52.6 ± 6.6. fmol/mg protein, respectively. These data indicate that STZ-induced diabetic rats exhibit supersensitivity to SP in the spinal cord. This may be correlated, in part, with the reduction in the threshold for perception of pain in diabetic animals.

Pharmacological studies of lappaconitine. Analgesia produced by intracerebroventricular, intracisternal and intrathecal injections.

The antinociceptive effects of lappaconitine (LA) and morphine (MOR) when injected intracerebroventricularly (i.c.v.), intracisternally (i.cist.) or intrathecally (i.t.) were investigated in mice by use of the tail pinch, hot plate and acetic acid-induced writhing tests. In addition, the effects of naloxone (NLX) administered subcutaneously on the antinociceptive action of LA and MOR were studied. LA and MOR after i.c.v., i.cist. and i.t. injection produced dose-dependent antinociception. MOR was more potent in the tail pinch and acetic acid-induced writhing tests by i.t. injection than by i.c.v. or i.cist. injection, but the potency in the hot plate test was independent of the injection site. On the other hand, like MOR, LA was more potent after i.t. injection than after i.c.v. or i.cist. injection in the tail pinch and acetic acid-induced writhing test. Its antinociceptive action was less potent than that of MOR. The antinociceptive actions of MOR were antagonized by NLX (1 mg/kg, s.c.) in every test and injection site, whereas the antinociceptive actions of LA were not inhibited, except for the antinociception on the tail pinch test, which was partially antagonized by NLX. It is suggested that LA mainly produced an NLX-resistant antinociceptive effect at the spinal site.

Dual action mechanisms of KK-3, a newly synthesized leu-enkephalin derivative, in the production of spinal analgesic effects.

The action mechanism for the production of spinal analgesia of KK-3, tyrosyl-N-methyl-gamma-aminobutylyl-phenylalaninol, was examined by the tail pinch and tail flick methods. Intrathecal KK-3, 2.5, 5 and 10 nmol/mouse, dose-dependently produced an analgesic effect in both methods. In the tail pinch method, the analgesia was suppressed by 2 mg/kg but not by 1 mg/kg of naloxone; however, the analgesic effect was significantly antagonized by 1 and 2 mg/kg Mr2266, a kappa-antagonist. Meanwhile, both naloxone and Mr2266 failed to block the analgesic effect of KK-3 in the tail flick test. Intrathecal capsaicin, 0.3, 3 and 15 nmol/mouse, also produced a dose-dependent analgesic effect in the tail flick test, whereas no appreciable analgesia could be found in the tail pinch test. Neither naloxone nor Mr2266 blocked the analgesic effect of capsaicin. The results indicate that KK-3 may possess two separate pharmacological mechanisms for the production of analgesic effects on the spinal level: one is the depletion of substance P following its release from the spinal cord, and the other is the mediation through kappa-opioid receptors.

Dual Action Mechanisms of KK-3, a Newly Synthesized Leu-Enkephalin Derivative, in the Production of Spinal Analgesic Effects

AbstractThe action mechanism for the production of spinal analgesia of KK-3, tyrosyl-N-methyl-γ-aminobutylyl-phenylalaninol, was examined by the tail pinch and tail flick methods. Intrathecal KK-3, 2.5, 5 and 10 nmol/mouse, dose-dependently produced an analgesic effect in both methods. In the tail pinch method, the analgesia was suppressed by 2 mg/kg but not by 1 mg/kg of naloxone; however, the analgesic effect was significantly antagonized by 1 and 2 mg/kg Mr2266, a κ-antagonist. Meanwhile, both naloxone and Mr2266 failed to block the analgesic effect of KK-3 in the tail flick test. Intrathecal capsaicin, 0.3, 3 and 15 nmol/mouse, also produced a dose-dependent analgesic effect in the tail flick test, whereas no appreciable analgesia could be found in the tail pinch test. Neither naloxone nor Mr2266 blocked the analgesic effect of capsaicin. The results indicate that KK-3 may possess two separate pharmacological mechanisms for the production of analgesic effects on the spinal level: one is the depletion of substance P following its release from the spinal cord, and the other is the mediation through κ-opioid receptors

Studies on analgesic oligopeptides. VI. Further studies of synthesis and biological properties of tripeptide alkylamides, Tyr-D-Arg-Phe-X.

Nine analogs based on a structure of Tyr-D-Arg-Phe-X (X = alkylamides or alkylhydrazide containing electron-withdrawing atoms or groups) were newly synthesized and their biological properties were examined by the opioid receptor binding properties of mu-, delta- and kappa-receptors, guinea-pig ileum (GPI) assay and analgesic activity in the tail pinch test after subcutaneous administration in mice. Analogs with X = NHCF2CF3, Sar-ol, or NH(CH2)2CN showed potent activities in the GPI and analgesic assays and high affinity for mu-receptor. An analog with X = taurinamide was found to possess 4-fold higher mu-receptor selectivity than that of [D-Ala2, MePhe4, Gly-ol5]enkephalin (DAGO). The receptor binding properties of previously reported analogs [Chem. Pharm. Bull., 33, 1528 (1985); ibid., 33, 4865 (1985); ibid., 36, 4834 (1988)] were also examined for overall discussion of the structure-activity relationships of this series of tripeptide amides.

Synthesis and biological activity of (MeTyr1,MeArg7,D-Leu8)-dynorphin A(1-9)-NHEt and (D-Cys2-Cys5,MeArg7,D-Leu8)-dynorphin A(1-9)-NH2.

The opioid activities of [MeTyr1]-Dyn(1-7)-NH2, [MeTyr1,D-Leu8]-Dyn(1-8)-NH2, [MeTyr1,D-Leu8]-Dyn(1-9)-NH2, [MeTyr1,D-Leu8]-Dyn(1-10)-NH2, [MeTyr1,D-Leu8]-Dyn(1-11)-NH2, and [MeTyr1,D-Leu8,12]-Dyn(1-13)-NH2 were examined in the bioassays (guinea pig ileum, mouse vas deferens and rabbit vas deferens). Because [MeTyr1,D-Leu8]-Dyn(1-9)-NH2 showed the most potent opioid activity of the peptides tested, the biological activities of two kinds of Dyn(1-9) analogues, [MeTyr1,MeArg7,D-Leu8]-Dyn(1-9)-NHEt and [D-Cys2-Cys5,MeArg7,D-Leu8]-Dyn(1-9)-NH2 were determined and compared with those of [MeTyr1,MeArg7,D-Leu8]-Dyn(1-8)-NHEt and [D-Cys2-Cys5,MeArg7,D-Leu8]-Dyn(1-8)-NHEt in the three bioassays, in the receptor binding assays, and in the mouse tail pinch test after subcutaneous administration. The results suggest that the extension of the C-terminal in the peptide chain of [MeArg7,D-Leu8]-Dyn(1-8)-NH2 analogues by Arg is ineffective for increasing the kappa-opioid activities, kappa-receptor selectivity and/or analgesic effects of the peptides.

Synthesis and structure-activity relationships of dynorphin A-(1-8) amide analogs

In order to study the structure-activity relationships of dynorphin A-(1-8) amide [Dyn(1-8)-NH2], 20 analogues were synthesized by the solution method. Their biological activities were determined in the three bioassays [guinea pig ileum (GPI), mouse vas deferens (MVD), and rabbit vas deferens (RVD)] and in the mouse tail-pinch test after intravenous administration. Some analogues that showed interesting activity in the bioassays and/or in the analgesic tests were further characterized in mu-, delta-, and kappa-representative binding assays. The obtained data indicate that modification of the enkephalin segment to give metabolically stable analogues with high affinity and selectivity for the kappa receptor is strictly limited and that introduction of MeArg in position 7 protects the Arg6-Arg-7 bond from enzymatic degradation without potency drop and change of opioid receptor selectivity. [MeTyr1,MeArg7,D-Leu8]Dyn(1-8)-NHEt (18) [IC50 (nM) = 0.3 (GPI), 7.4 (MVD), and 2.6 (RVD); tail pinch ED50 (mg/kg) = 0.75] showed opioid activity similar to that of dynorphin A in the three bioassays and relatively high kappa-receptor selectivity in the binding assays and produced a 2.5-fold more potent analgesic effect than morphine. [D-Cys2-Cys5,MeArg7,D-Leu8]Dyn(1-8)-NHEt (20) showed a 40-60-fold more potent opioid activity than 18 in the three bioassays and produced a 3.4-fold more potent analgesic effect than 18. In the binding assays, however, 20 showed higher affinity for mu and delta receptors than for the kappa receptor.

Synthesis and structure-activity relationships of (MeTyr1, MeArg7)-Dynorphin A(1-8)-OH analogues with substitution at position 8.

A series of [MeTyr1, MeArg7]-Dynorphin A (Dyn)(1-8)-OH analogues, modified at position 8 with various amino acids, is described. Their biological activities were determined in the three bioassays [guinea pig ileum (GPI), mouse vas deferens (MVD), and rabbit vas deferens (RVD)] and in the mouse tail-pinch test after subcutaneous administration. None of the analogues tested displayed more potent kappa-opioid activity in the RVD than [MeTyr1, MeArg7, D-Leu8]-Dyn(1-8)-NHEt (1), which is a potent analgesic peptide with similar opioid receptor selectivity to that of Dyn. However, [MeTyr1, MeArg7, Melle8]-Dyn(1-8)-OH (11) showed about a twofold more potent analgesic effect than 1. Based on the obtained results it is conceivable that in the case of Dyn(1-8)-OH analogues both a lipophilic L-amino acid in position 8 and an unchanged 7-8 amide bond are essential to maintain potent kappa-opioid activity.

Effects of chronic haloperidol on stress-induced oral behaviour in rats

Rats received daily injections of haloperidol (HAL, 5 mg/kg SC, or IP) or tartaric acid vehicle for 14-21 days. Four to six days after discontinuation of the daily injections, rats were given a single 5-min tail pinch (TP) test. HAL-treated rats showed significantly shorter latencies to display oral behaviours (OB: licking, gnawing, or drinking) compared to controls in five separate replications. Food consumption per se was not consistently affected. Shorter OB latencies were significantly correlated both with increased striatal 3H-spiperone binding and with apomorphine stereotypy scores. In a final experiment, this effect of HAL on OB latencies was blocked by a systemic injection of naloxone (2 mg/kg IP) prior to the TP test. Naloxone did not affect OB latency in control rats, suggesting the possibility of endogenous opiate involvement in the chronic HAL effects. The overall results suggest that OB latencies following mildly activating stimulation may provide a useful behavioural assay for neuroleptic-induced oral abnormalities as well as a functional index of striatal dopamine D-2 receptor sensitivity.

Involvement of spinal noradrenergic system in the mechanism of an antinociceptive effect of delta-sleep-inducing peptide (DSIP)

We studied whether the antinociceptive effect produced by intracerebroventricular injection of delta-sleep-inducing peptide (DSIP) to mice involved the monoaminergic pathways that descended from brainstem to spinal cord (the descending inhibitory systems). In the tail-pinch test, the antinociceptive effect of DSIP was significantly reduced by the pretreatment with reserpine (3 mg/kg i.p.) which depleted endogenous monoamines. Moreover, the intrathecal injections of monoamine antagonists were performed to evaluate the roles of the spinal noradrenergic and/or serotonergic systems in the production of the DSIP antinociception. In both tail-pinch and hot plate tests, the antinociceptive effect of DSIP was significantly antagonized by the previous intrathecal administration of phentolamine (an α-adrenergic blocker) or yohimbine (an α 2-adrenergic blocker), but was unaffected by the pretreatment with methysergide (a serotonin antagonist). These results demonstrate that the activation of the descending inhibitory systems, mainly spinal noradrenergic systems, is involved in the elicitation of DSIP antinociception.

Antinociceptive effects of azepexole (BHT 933) in mice

Subcutaneous (s.c.) administration of azepexole (BHT 933) at doses between 4 and 40 mg/kg produced dose-dependent antinociceptive effects in mice as assessed by tail-immersion, tail-pinch and acetic acid writhing tests. The ED 16s were 5.6 ± 0.4, 6.7 ± 1.2 and 2.96 ± 0.2 mg/ kg respectively. Similarly, morphine produced analgesia in the same tests with ED 16s of 0.87 ± 0.03, 0.47 ± 0.1 and 0.45 ± 0.01 mg/ kg respectively. In all instances naloxone (0.1 mg/kg s.c.) shifted the dose-response curves to morphine to the right in a parallel manner. Naloxone (0.1 and 1 mg/kg s.c.) partially antagonized the effect of azepexole in the tail-immersion and tail-pinch tests but significantly decreased the slope of the dose-response curve suggesting that a competitive interaction at the level of the opioid receptors did not occur. Naloxone had no effect on the antinociceptive action of azepexole in the acetic acid writhing test.