Antinociception induced by intraperitoneal injection of gentamicin in rats and mice

Purification and function of two analgesic and anti-inflammatory peptides from coelomic fluid of the earthworm, Eisenia foetida

The potential application of anti-inflammatory and analgesic compounds in medication and therapeutic care have become of increasing interest. We purified and characterized two novel analgesic and anti-inflammatory peptides, VQ-5 and AQ-5, from the coelomic fluid of the earthworm (Eisenia foetida). Their primary structures were determined as VSSVQ and AMADQ, respectively. Both peptides, especially AQ-5, exhibited analgesic activity in mouse models of persistent neuropathic pain and inflammation. AQ-5 also inhibited tumor necrosis factor alpha and cyclooxygenase-2 production. The mitogen-activated protein kinase signaling pathway, which is involved in analgesic and anti-inflammatory functions, was inhibited by AQ-5. Thus, the analgesic and anti-inflammatory effects of these peptides, especially AQ-5, demonstrated their potential as candidates for the development of novel analgesic medicines.

Neamine and 2-deoxystreptamine neomycin derivatives exhibit antinociceptive activity in rat models of phasic, incision and neuropathic pain

OBJECTIVES

To assess the antinociceptive activity of the neomycin derivatives neamine and 2-deoxystreptamine following intraspinal administration in rats.

METHODS

We used the tail-flick test and measured the threshold to mechanical stimulation in models of incisional and neuropathic pain.

KEY FINDINGS

The derivatives produced antinociception in the tail-flick test and reduced mechanical allodynia in models of incisional and neuropathic pain. The approximate ED50 in milligrams (confidence limits in parenthesis) in these tests were 1.35 mg (0.61; 2.95), 0.20 mg (0.14; 0.27) and 0.28 mg (0.12; 0.63) for neamine, and 1.05 mg (0.68; 1.60), 0.78 mg (0.776; 0.783) and 0.79 mg (0.46; 1.34) for 2-deoxystreptamine, respectively. Neamine was more potent than 2-deoxystreptamine in the incisional and neuropathic pain models, but they had similar potency in the tail-flick test. Tetra-azidoneamine, a neamine derivative in which free amino groups are replaced with azido groups, did not change the incisional mechanical allodynia. The reduction of incisional allodynia by neamine and 2-deoxystreptamine was transitorily antagonized by intrathecal administration of calcium chloride.

CONCLUSIONS

The intraspinal administration of neamine and 2-deoxystreptamine is antinociceptive in rats. The presence of amino groups in the structure of these derivatives is fundamental to their antinociceptive effect, which may be due to a calcium antagonist activity.

Evaluation of analgesic activity of levofloxacin in human experimental pain model

BACKGROUND

Levofloxacin, an optically active isomer of ofloxacin, exerts broad spectrum antibacterial activity. Apart from its antibacterial action, experimental studies have documented antinociceptive properties in animal pain models suggesting an analgesic effect. This study was conducted with the aim to evaluate the analgesic activity of levofloxacin in healthy human volunteers.

METHODS

This was an open label, prospective, non-randomized, interventional study conducted on 12 apparently healthy volunteers at a tertiary care teaching hospital in India. Permission from the Institutional Ethics Committee was obtained. After obtaining informed consent, volunteers fulfilling the inclusion criteria were enrolled. Analgesic activity was assessed by Cola cap and sphygmomanometer, a human experimental pain model. Observation of pain threshold and tolerance was recorded at baseline and at an interval of 2 h and 4 h after administration of levofloxacin (500 mg oral) in all 12 subjects. The results were analysed using repeated measures one way analysis of variance.

RESULTS

The mean age of the volunteers was 27.5±3.26 years. A statistically significant increase in the pain threshold and tolerance was found at 2 h and 4 h when compared to baseline.

CONCLUSIONS

Levofloxacin exhibited significant analgesic activity in a human pain model and can be used in infections associated with pain or for pre-operative prophylaxis. Further investigations are required to understand the precise mechanism and pathway of antinociception exhibited by levofloxacin.

Design, synthesis, biological evaluation, and comparative Cox1 and Cox2 docking of p-substituted benzylidenamino phenyl esters of ibuprofenic and mefenamic acids

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently associated with gastric mucosal and renal adverse reactions, related to inhibition of cyclooxygenase1 (Cox1) in tissues where prostaglandins exert physiological effects. This led us to develop a set of ibuprofenic acid and mefenamic acid esters, namely: 4-((4-substituted benzylidene)amino)phenyl 2-(4-isobutylphenyl)propanoate and 4-((4-substituted benzylidene)amino)phenyl 2-((2,4-dimethylphenyl)amino)benzoate analogs, which were synthesized by condensation of the corresponding acids with Schiff's bases [4-(4-substituted benzylideneamino)phenols] involving dicyclohexyl carbodiimmide (DCC) as mild dehydrating agent. The main objective is to reduce the GIT toxicity associated with acute and chronic NSAIDs use. Anti-inflammatory, analgesic as well as ulcerogenic activities of the prepared esters were evaluated in vivo and compared with that of ibuprofen as reference standard in all screenings, involving the carrageenan induced paw oedema model and hot plate method. Most of the synthesized esters showed remarkable analgesic and anti-inflammatory activities. Interestingly, all of the compounds were found to be non-ulcerogenic under the tested conditions. This evidence have suggested that modification of the carboxyl function of representative NSAIDs results in retained or enhanced anti-inflammatory and analgesic activities with reduced ulcerogenic potential. Additionally, a comparative AutoDock study into Cox 1 and Cox2 has been done involving both of rigid and flexible docking for potential selectivity of our compounds within different Cox enzymes and to find out the binding orientation of these novel esters into their binding site. Some of the newly prepared aforementioned compounds showed considerable more Cox2 over Cox1 binding affinities by flexible docking better than rigid one.

Analgesic and anti-inflammatory effects of the amphibian neurotoxin, anntoxin

Anntoxin is the first gene-encoded neurotoxin identified from amphibians, which is a 60-residue neurotoxin peptide, acting as an inhibitor of tetrodotoxin-sensitive (TTX-S) voltage-gated sodium channel (VGSC). Sodium channels have been considered as therapeutic targets for pain. Several animal models of persistent inflammatory and neuropathic pain (tail-flick test, hot plate test, acetic acid-induced writhing test, formalin-induced paw licking, carrageenan-induced paw edema) were used to test analgesic functions of recombinant anntoxin (r-anntoxin). In all these animal models, r-anntoxin showed strong analgesic functions. R-anntoxin obviously inhibited secretions of both tumor necrosis factor alpha (TNF-α) and cyclooxygenase-2 (COX-2). Histopathological study indicated that r-anntoxin reduced the edematous epidermis induced by carrageenan. All these results indicate that r-anntoxin has strong analgesic and anti-inflammatory activities.

Antinociceptive and anti-inflammatory effects of Costus spicatus in experimental animals

CONTEXT

Costus spicatus Swartz (Costaceae), commonly called "cana-do-brejo'" in Brazil's northeast, is a medicinal plant found in wet coastal forests. In folk medicine an infusion of the aerial parts is taken to treat inflammation and pain.

OBJECTIVE

The methanol extract obtained from the leaves of Costus spicatus (MECs) was evaluated for antinociceptive and anti-inflammatory activities.

METHODS

Analgesic and anti-inflammatory activities were studied by measuring nociception through acetic acid, formalin, and hot-plate tests, while inflammation was induced by carrageenan. All experiments were conducted with experimental animals.

RESULTS AND DISCUSSION

Following oral administration, MECs (100, 200, and 400 mg/kg) significantly reduced the number of writhes (52.8, 43.1, and 55.3%, respectively) in the writhing test and the number of paw licks during phase 1 (61.9, 54.1, and 92.1%) and phase 2 (62.5, 82.9, and 98.1%, all doses) during the formalin test when compared to the control group animals. The reaction time during the hot-plate test was increased significantly and was dose-dependent, whereas pretreatment with naloxone rigorously reduced the analgesic potential of MECs, which suggested participation of the opioid system in the modulation of pain induced by MECs. Such results were unlikely to be provoked by motor abnormality, as MECs-treated mice did not exhibit any performance alteration during the Rota-rod test. The administration of 200 and 400 mg/ kg (i.p.) of MECs exhibited an anti-inflammatory effect during the carrageenan test, which was based on interference with inflammatory mediator synthesis.

CONCLUSION

We conclude that MECs has antinociceptive and anti-inflammatory activities in rodents.

Studies on the analgesic, anti-inflammatory and antipyretic effects of Parquetina nigrescens leaf extract

ETHNOPHARMACOLOGICAL RELEVANCE

Parquetina nigrescens is a shrub that is commonly used in different parts of West Africa for the treatment of several ailments which includes pain, fever and inflammatory conditions.

AIM OF THE STUDY

The present study was designed to investigate the analgesic, anti-inflammatory and antipyretic effects of the aqueous extract of Parquetina nigrescens leaves in rats.

MATERIALS AND METHODS

Five groups were used for each study, groups 1 and 5 served as control (saline) and reference (indomethacine) respectively, while groups 2-4 received the extract (50-200 mg/kg) orally. Formalin paw licking and hot plate latency tests were used for analgesic studies. Carrageenan oedema, cotton pellet granuloma and formaldehyde arthritis models were used to quantify the anti-inflammatory activities while the brewer's yeast was used for inducing pyrexia.

RESULTS

The results of the analgesic study show that the extract produced significant (p<0.05) analgesia in the hot plate and in the formalin tests. In the anti-inflammatory study, Parquetina nigrescens produced significant (p<0.05) inhibition of the various types of inflammation. The extract also inhibited the pyrexia induced by brewer's yeast.

CONCLUSION

The result justifies the traditional uses of Parquetina nigrescens for the treatment of fever, inflammatory and painful conditions.

Mechanisms of the antinociceptive action of gabapentin

Gabapentin, a gamma-aminobutyric acid (GABA) analogue anticonvulsant, is also an effective analgesic agent in neuropathic and inflammatory, but not acute, pain systemically and intrathecally. Other clinical indications such as anxiety, bipolar disorder, and hot flashes have also been proposed. Since gabapentin was developed, several hypotheses had been proposed for its action mechanisms. They include selectively activating the heterodimeric GABA(B) receptors consisting of GABA(B1a) and GABA(B2) subunits, selectively enhancing the NMDA current at GABAergic interneurons, or blocking AMPA-receptor-mediated transmission in the spinal cord, binding to the L-alpha-amino acid transporter, activating ATP-sensitive K(+) channels, activating hyperpolarization-activated cation channels, and modulating Ca(2+) current by selectively binding to the specific binding site of [(3)H]gabapentin, the alpha(2)delta subunit of voltage-dependent Ca(2+) channels. Different mechanisms might be involved in different therapeutic actions of gabapentin. In this review, we summarized the recent progress in the findings proposed for the antinociceptive action mechanisms of gabapentin and suggest that the alpha(2)delta subunit of spinal N-type Ca(2+) channels is very likely the analgesic action target of gabapentin.

Safety of blocking vascular adhesion protein-1 in patients with contact dermatitis

Vascular adhesion protein-1 mediates leukocyte binding to vascular endothelia and migration to tissues. It is upregulated in inflammatory conditions. We studied the safety of vascular adhesion protein-1 blockade by a single dose of the mouse monoclonal antibody vepalimomab in patients with nickel-induced allergic contact dermatitis lesions. Vepalimomab, 0.05-0.50 mg kg(-1) was safe and well tolerated. Four of nine patients reported adverse events of mild to moderate intensity. Human antimouse antibodies were detected after infusion in all the patients and they remained above the basal level for at least one month. Vepalimomab dose-dependently labelled vascular adhesion protein-1 in the inflamed skin. Luminal upregulation of vascular adhesion protein-1 on the endothelium upon inflammation was demonstrated for the first time in patients in vivo. Vepalimomab was found on the endothelium up to 24 hr after dosing whilst it was cleared from the circulation with an apparent half-life of 25-50 min. The results provide in vivo support for the concept of blocking vascular adhesion protein-1 in human disease states and support previous proposals that vascular adhesion protein-1 is a potential target molecule for inhibition of inflammatory reactions.

Analgesic and anti-inflammatory properties of Nelsonia canescens leaf extract

An ethanolic extract of the dried leaves of Nelsonia canescens was investigated for anti-inflammatory and analgesic activities in rat. In the test for anti-inflammatory activity, the extract at the doses of 50-200 mg/kg significantly (P<0.05) inhibited carrageenan-induced paw oedema and cotton pellet granuloma. Likewise, at the same doses the extract exhibited analgesic activity in both the hot plate latency assay (hot plate maintained at 55 degrees C) and on the early and late phases of formalin-induced paw licking in rats. The result of the present study confirm that Nelsonia canescens has analgesic and anti-inflammatory activities. These findings also justify the traditional use of the plant for treating pain.

Studies on the anti-inflammatory and analgesic properties of Tithonia diversifolia leaf extract

A methanol extract of the dried leaves of Tithonia diversifolia was investigated for anti-inflammatory and analgesic activities. The extract (50-200 mg/kg, p.o.) produced dose-related inhibition of carrageenan-induced paw oedema and cotton pellet-induced granuloma in rats. At the same doses, analgesic effect was also observed with hot plate latency assays maintained at (55 degrees C) as well as on the early and late phases of formalin-induced paw licking in rats. The results of the present study further confirm the use of Tithonia diversifolia traditionally for the treatment of painful inflammatory conditions.

Antinociceptive potency of aminoglycoside antibiotics and magnesium chloride: a comparative study on models of phasic and incisional pain in rats

A close relationship exists between calcium concentration in the central nervous system and nociceptive processing. Aminoglycoside antibiotics and magnesium interact with N- and P/Q-type voltage-operated calcium channels. In the present study we compare the antinociceptive potency of intrathecal administration of aminoglycoside antibiotics and magnesium chloride in the tail-flick test and on incisional pain in rats, taken as models of phasic and persistent post-surgical pain, respectively. The order of potency in the tail-flick test was gentamicin (ED50 = 3.34 microg; confidence limits 2.65 and 4.2) > streptomycin (5.68 microg; 3.76 and 8.57) = neomycin (9.22 microg; 6.98 and 12.17) > magnesium (19.49 microg; 11.46 and 33.13). The order of potency to reduce incisional pain was gentamicin (ED50 = 2.06 microg; confidence limits 1.46 and 2.9) > streptomycin (47.86 microg; 26.3 and 87.1) = neomycin (83.17 microg; 51.6 and 133.9). The dose-response curves for each test did not deviate significantly from parallelism. We conclude that neomycin and streptomycin are more potent against phasic pain than against persistent pain, whereas gentamicin is equipotent against both types of pain. Magnesium was less potent than the antibiotics and effective in the tail-flick test only.

Involvement of calcium in pain and antinociception

Calcium ions are widely recognized to play a fundamental role in the regulation of several biological processes. Transient changes in cytoplasmic calcium ion concentration represent a key step for neurotransmitter release and the modulation of cell membrane excitability. Evidence has accumulated for the involvement of calcium ions also in nociception and antinociception, including the analgesic effects produced by opioids. The combination of opioids with drugs able to interfere with calcium ion functions in neurons has been pointed out as a useful alternative for safer clinical pain management. Alternatively, drugs that reduce the flux of calcium ions into neurons have been indicated as analgesic alternatives to opioids. This article reviews the manners by which calcium ions penetrate cell membranes and the changes in these mechanisms caused by opioids and calcium antagonists regarding nociceptive and antinociceptive events.

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.

Modulation of the activity of midbrain central gray substance neurons by calcium channel agonists and antagonists in vitro

Changes in the background impulse activity of midbrain central gray substance neurons have been studied on slice preparations from the rat midbrain upon application of calcium-free solution, an activator of calcium channels, BAY-K 8644 (10 nM), organic (verapamil, 40 microM; D600, 10 microM; nifedipine, 1-10 microM; amiloride, 1 microM) and inorganic (Co2+, 1.5 mM) calcium channel blockers. Besides BAY-K 8644, all the substances inhibited most of the neurons studied. Verapamil, BAY-K 8644 and Co2+ also revealed facilitatory effects. Facilitatory action of BAY-K was most effective in silent neurons and in those previously inhibited by amiloride. Latent period values of inhibition in calcium-free solution and upon application of organic and inorganic blockers have the following sequence: D600 > amiloride > verapamil > Co2+ > nifedipine > calcium-free solution. Maximum rise time had the following order: amiloride > D600 > nifedipine > verapamil > Co2+ > calcium-free solution. Complete suppression of the neuronal activity induced by amiloride lasted twice as long as that induced by calcium-free solution, Co2+ and nifedipine, and six times as long as verapamil-induced suppression. Preliminary application of calcium channel blockers reduced facilitatory and increased inhibitory effects of serotonin and substance P. Data obtained are discussed with the supposition in mind that inhibition of the function of calcium channels in central gray substance neurons could be one of the mechanisms underlying the analgesic effect of a series of neurotropic agents after their introduction into this structure.

Influence of omega-conotoxin on morphine analgesia and withdrawal syndrome in rats

The effect of omega-conotoxin on opiate analgesia and withdrawal syndrome was investigated in rats. omega-Conotoxin given i.c.v. and i.p. caused weak analgesia in the tail-flick test. When the toxin (20 ng/rat) was given i.c.v. immediately before morphine (1.5 micrograms/rat i.c.v.) the resultant analgesic effect was additive. In contrast, the analgesia elicited by morphine (3 micrograms/rat i.c.v.) was greatly reduced after 24-h pretreatment with the toxin (20 ng/rat i.c.v.). The systemic administration of the toxin (10 micrograms/kg i.p.) did not affect morphine analgesia whether omega-conotoxin was coadministered with morphine (2.5 mg/kg i.p.) or was given 24 h before the opiate (5 mg/kg i.p.). omega-Conotoxin i.c.v. injected in morphine-dependent rats 15 min before naloxone challenge significantly attenuated the abstinence syndrome. On the contrary systemic administration of omega-conotoxin failed to suppress the morphine withdrawal syndrome. The present results suggest that omega-conotoxin affects both acute and chronic effects of morphine.

Antinociception induced by intracerebroventricular or intrathecal administration of gentamicin in rats

1. The intrathecal (i.t.) administration of gentamicin (AD50 = 3.98 micrograms) produced marked and dose-dependent antinociception in rats, as assessed by the tail-flick test. A weaker effect was obtained following intracerebroventricular drug administration (AD50 = 50.12 micrograms). 2. A transitory but dose-dependent antagonism of the effect of i.t. gentamicin was obtained following i.t. administration of calcium chloride (4 and 8 micrograms). 3. The magnitude and duration of morphine antinociception (5 micrograms, i.t.) were enhanced by the previous (intraperitoneal) i.p. or i.t. administration of gentamicin. 4. These results indicate that gentamicin-induced antinociception may depend on its calcium-antagonist property and involves drug diffusion to a spinal site of action.

Analgesic effects of centrally administered aminoglycoside antibiotics in mice

The possible analgesic effects of i.c.v. administration of several aminoglycoside antibiotics were evaluated in mice using hot plate and tail flick tests. Neomycin (10-80 micrograms/mouse), gentamicin (40-160 micrograms/mouse) and kanamycin (80-320 micrograms/mouse) produced dose-dependent increases in the latencies to forepaw licking and jumping in hot plate test. These drugs also produced dose-dependent increases in the percentage of animals showing analgesia in tail flick test. The order of potency of these aminoglycoside antibiotics in both tests was neomycin greater than gentamicin greater than kanamycin, which is exactly the same order that these drugs show as N-type calcium channel blockers. Bearing in mind this fact and the well known analgesic activity of several drugs which decrease neuronal calcium availability, we suggest that the mechanism of aminoglycoside-induced antinociception may be related to the capacity of these antibiotics to block N-type calcium channels and decrease neuronal calcium availability.