Analgesic Activity In Mice Research Articles

Synthesis and biological evaluation of N-antipyrine-4-substituted amino-3-chloromaleimide derivatives

This paper describes the synthesis of new cyclic imides obtained by reaction with N-antipyrine-3,4-dichloromaleimides and different aromatic amines. The analgesic activity of the synthesized compounds was initially investigated against the writhing test in mice, followed by analysis of the most promising compounds in this model and in the formalin-induced model. The results indicate that the compounds containing the electron-withdrawing substituents in the para position of the substitute ring exerted more potent analgesic activity in mice, being much more potent than the prototype N-antipyrine-3,4-dichloromaleimide and some reference drugs. Some compounds exhibited activity against human opportunistic and pathogenic fungi, with MIC values of between 40 and 100 μg/mL (91.74 and 236.96 μM), and it was verified that only a few compounds presented potential for cytotoxic activity.

Antioxidant and Analgesic Activities of Pterocarpus marsupium Roxb

The methanolic extract of the bark of Pterocarpus marsupium Roxb. (Papilionaceae) was screened for antioxidant activity in vitro and analgesic activity in mice, respectively. The in vitro antioxidant activity of the bark extract was evaluated using the 1,1-diphenyl-2-picrylhydrazyl assay, and the results were expressed as IC50. Ascorbic acid, used as a standard, had an IC50 = 34.0 μg mL−1, whereas the bark extract of P. marsupium had an IC50 = 53.0 μg mL−1. Use of the hot-plate method to study central analgesic activity of the bark extract in mice indicated that the bark extract of P. marsupium possesses the ability to significantly reduce pain threshold and also increase the response latency period to thermal stimuli in mice, similar to the reference drug pentazocine. The reaction time of mice was significantly increased to 2 hr with 500 mg mL−1 of bark extract, whereas pentazocine also increased reaction time to 2 hr with 5 mg kg−1. A decline in the reaction time beyond 3 hr was observed by the reference drug and bark extract.

Synthesis of N-substituted 4,6-dioxo-imidazo[3,4-c] thiazoles and their analgesic activity in mice.

A new series of N-substituted dioxo-imidazo[3,4-c]thiazoles have been prepared and evaluated for their analgesic activity. The structures of these new derivatives were confirmed by lR, 1H NMR and 13C NMR spectra, and by elemental analysis. When administered intraperitoneally to mice all derivatives were devoid of any toxic effect, even at the high dose of 800 mg kg(-1). In the phenylbenzoquinone-induced abdominal constriction test in mice, eight of the nine synthesized compounds exhibited significant antinociceptive properties with ED50 values (50% effective dose) ranging from 46.7 to 104.7 mg kg(-1) intraperitoneally. Further investigation demonstrated that analgesic activity of the most effective derivatives 5e and 5f partly involved opioidergic and/or noradrenergic pathways.

Isolation of opioid-active compounds from Tabernaemontana pachysiphon leaves.

A procedure for prefractionation of crude plant extracts by centrifugal partition chromatography (CPC) has been developed to enable rapid identification of known-positive compounds or false-positive compounds and to increase the chance of identifying minor unknown-active compounds. The study explored the use of CPC as a tool in the prefractionation step before investigation of bioactivity. Fractions obtained by CPC from an ethanolic extract of Tabernaemontana pachysiphon Stapf (Apocynaceae) were screened by means of an opiate-receptor-binding assay and an adenosine A1-receptor-binding assay. Fractions containing fatty acids, which had false-positive effects on the assay, were identified, as were unknown-positive fractions from which two opioid-active compounds, tubotaiwine and apparicine, were subsequently isolated. The affinities (Ki) of tubotaiwine and apparicine at the opiate receptor were 1.65 +/- 0.81 and 2.65 +/- 1.56 micromol, respectively. Both alkaloids had analgesic activity in the abdominal constriction test in mice. CPC prefractionation led to the rapid isolation of two opioid-active compounds, tubotaiwine and apparicine, from the unknown-positive fraction; false-positive fractions were rapidly identified. Both tubotaiwine and apparicine had affinity for adenosine receptors in the micromolar range and also had in-vivo analgesic activity in mice.

Evaluation of analgesic and anti-inflammatory activities of Oscillatoria willei in experimental animal models

The methanol extract of oscillatoria willei (MECO) was investigated by hot plate and acetic acid induced writhing method to assess its analgesic activity. The extract was evaluated using carrageenan induced paw oedema method and cotton pellet induced granuloma method for its effect on acute and chronic phase inflammation models in rat as well as analgesic activity in mice. It was found that extract caused an inhibition on writhing response induced by acetic acid in a dose dependant manner. Maximum inhibition (67%) was obtained at a dose of 200 mg/kg after 3 h of drug treatment in carrgeenan induced paw oedema whereas indomethacin (standard drug) produced 61.65% inhibition in chronic model (cotton pellet induced granuloma) the MECO and standard drug showed decreased formulation of granuloma tissue. The result indicates significant analgesic and anti–inflammatory effects and therapeutic efficacy of MECO on animal models which are comparable with those of standard drugs. Key words: Oscillatoria willei, analgesic, carrageenan induced paw oedema.

The Rac GTPase-activating bacterial protein toxin CNF1 induces analgesia up-regulating μ-opioid receptors

Cytotoxic Necrotizing Factor 1 (CNF1) is a protein toxin from Escherichia coli that constitutively activates the Rho, Rac and Cdc42 GTPases. These regulatory proteins oscillate between a cytosolic GDP-bound inactive form and a membrane-linked GTP-bound active form, orchestrating the actin cytoskeleton assembly and dynamics. We herein describe, for the first time, the ability of CNF1 to potently counteract the formalin-induced inflammatory pain in mice. The analgesic response due to CNF1 requires both the sustained activation of the Rac GTPase, with consequent cerebral actin cytoskeleton remodeling, and the up-regulation of the μ-opioid receptors (MORs), the most important receptors controlling pain perception. The crucial role of Rac is proved by the lack of analgesic activity in mice challenged with a recombinant CNF1, in which the enzymatic activity was abolished by substituting serine with cysteine at position 866. The importance of MORs is proved by the inability of CNF1 to induce any analgesic effect in MORs knockout mice and by the ability of naloxone to antagonize the analgesic effects. Furthermore, it is worth noting that the analgesic effect in mice occurs after both peripheral and central administration of CNF1. Hence, taken altogether, our findings provide new insights into the comprehension of intracellular mechanisms involved in pain modulation, and indicate this bacterial protein toxin as a novel tool in the field of pain control. Conceivably, this might pave the way for new therapeutic strategies.

Antinociceptive activity of 1-nitro-2-phenylethane, the main component of Aniba canelilla essential oil

Aniba canelilla (H.B.K.) Mez is a medicinal plant used in the Amazon folk therapeutic as antispasmodic, antidiarreic, carminative, tonic agent and a stimulant of the digestive and central nervous system. Our preliminary studies showed that the plant essential oil has analgesic activity in mice. Now, we are reporting the antinociceptive effect of the compound 1-nitro-2-phenylethane (97.5%), the main component of the essential oil of Aniba canelilla, which was obtained by column chromatographic purification. In the writhing test this compound was dosed at 15, 25 and 50 mg/kg reducing the abdominal writhes in a significant manner; in the hot plate test it was assayed at 50, 100 and 200 mg/kg producing no alterations in the latency time when compared to the control; and in the formalin test the 1-nitro-2-phenylethane was tested at 50 and 25 mg/kg decreasing significantly the second phase of the algic stimulus. The study suggests that the 1-nitro-2-phenylethane has analgesic activity, probably of peripheral origin. The mechanism involved is not completely understood, however, the results suggest that the opioid receptors are involved in the antinociceptive action observed to 1-nitro-phenylethane.

Structure, Dynamics, and Selectivity of the Sodium Channel Blocker μ-Conotoxin SIIIA

mu-SIIIA, a novel mu-conotoxin from Conus striatus, appeared to be a selective blocker of tetrodotoxin-resistant sodium channels in frog preparations. It also exhibited potent analgesic activity in mice, although its selectivity profile against mammalian sodium channels remains unknown. We have determined the structure of mu-SIIIA in aqueous solution and characterized its backbone dynamics by NMR and its functional properties electrophysiologically. Consistent with the absence of hydroxyprolines, mu-SIIIA adopts a single conformation with all peptide bonds in the trans conformation. The C-terminal region contains a well-defined helix encompassing residues 11-16, while residues 3-5 in the N-terminal region form a helix-like turn resembling 3 10-helix. The Trp12 and His16 side chains are close together, as in the related conotoxin mu-SmIIIA, but Asn2 is more distant. Dynamics measurements show that the N-terminus and Ser9 have larger-magnitude motions on the subnanosecond time scale, while the C-terminus is more rigid. Cys4, Trp12, and Cys13 undergo significant conformational exchange on microsecond to millisecond time scales. mu-SIIIA is a potent, nearly irreversible blocker of Na V1.2 but also blocks Na V1.4 and Na V1.6 with submicromolar potency. The selectivity profile of mu-SIIIA, including poor activity against the cardiac sodium channel, Na V1.5, is similar to that of the closely related mu-KIIIA, suggesting that the C-terminal regions of both are critical for blocking neuronal Na V1.2. The structural and functional characterization described in this paper of an analgesic mu-conotoxin that targets neuronal subtypes of mammalian sodium channels provides a basis for the design of novel analogues with an improved selectivity profile.

Evaluation of Anti-inflammatory and Analgesic Activity of Root Extract of Solanum Trilobatum Linn

Methanolic extract of Solanum trilobatum Linn. (MEST) belonging to the family of Solanacea was evaluated by hot plate and acetic acid induced writhing methods to assess its analgesic activity. The extract was also evaluated for its anti-inflammatory activity by subjecting into carrageenan, and cotton pellet induced granuloma tests for its effect on acute and chronic phase inflammation models in rats, as well as analgesic activity in mice. It was found that the extract caused an inhibition on the writhing response induced by acetic acid in a dose dependent manner. 300 mg/kg doses of MEST and indomethacin could block the writhing response by 46.68% and 73.73% (p < 0.05), respectively. It was also indicated that the MEST showed significant (p < 0.001) antinociceptive action in hot plate reaction time method in mice. This effect was comparable to that of standard drug pentazocine treated controls, suggesting the central activity of MEST. Maximum inhibition (56.71%) was obtained at a dose of 100 mg/kg after 3 h of drug treatment in carrageenan induced paw oedema, whereas indomethacin (standard drug) produced 57.65% of inhibition. In the chronic model (cotton pellet induced granuloma) the MEST 300 mg/kg, indomethacin and dexamethasone standard drug showed decreased formation of granuloma tissue by 21.48%, 29.63% and 34.84%, respectively. The results indicate the potent analgesic and anti-inflammatory effects and therapeutic efficacy of Solanum trilobatum extract on animal models which are comparable with those of standard drugs such as pentazocine, indomethacin and dexamethasone, respectively.

Analgesic activity of the ethanolic extract of Aphanamixis polystachya bark

Ethanolic extract of Aphanamixis polystachya bark was used to investigate its analgesic activity by acetic acid induced writhing in mice. The bark extract exhibited statistically significant and dose dependent analgesic activity in mice. The bark extract at the doses of 250 and 500 mg/kg body weight showed 40.69% and 62.07% writhing inhibition respectively in mice whereas diclofenac-Na produced 75.17% writhing inhibition as a positive control.

Antinociceptive Activity of Methanolic Extract of Epilobium hirsutum

Antinociceptive activity of methanolic extract of aerial parts of Epilobium hirsutum (EH) was determined in the Hot plate and writhing tests in mice. Nearly all extracts showed a dose dependent and marked analgesic activity in mice in the thermal and chemical models of analgesia when compared to the control. Methanol extract at dose of 500 mg kg(-1) showed higher activity (97.7% writhing inhibition) than diclofenac 50 mg kg(-1) i.p., (77.8%, p<0.05) and morphine 5 mg kg(-1) i.p. (91.2%, p<0.05). Methanol extract, in all tested doses (200-500 mg kg(-1)) significantly increased the pain threshold in hot plate test (p<0.05). EH extract at 200 mg kg(-1) showed a similar effect to morphine at 5 mg kg(-1). These finding indicate the potential therapeutic use of methanolic extract of aerial parts of EH as a potent antinociceptive agent. LD50 was obtained 1.5+/-0.1 g kg(-1). EH extract did not induce locomotor impairment in mice at any tested doses.

Opiate and acetylcholine-independent analgesic actions of crotoxin isolated from crotalus durissus terrificus venom

The venom of Crotalus durissus terrificus is reported to have analgesic activity and the administration of Crotoxin (Cro) to cancer patients is reported to reduce the consumption of analgesics. This study investigated the analgesia induced by Cro and the effects of atropine and naloxone on the antinociceptive activity of Cro in mice and rats. The results showed that Cro at 66.5, 44.3 and 29.5 μg/kg (ip) exhibited a dose-dependent analgesic action in mice using the hotplate and acetic acid writhing tests. Cro at 44.3 μg/kg (ip) had significant analgesic action in the rat tail-flick test. In the mouse acetic acid-writhing test, intracerebral ventricular administration of Cro 0.3 μg/kg produced marked analgesic effects. Microinjection of Cro (0.15 μg/kg) into the periaqueductal gray area also elicited a robust analgesic action in rat hotplate test. Atropine at 0.5 mg/kg (im) or 10 mg/kg (ip) or naloxone at 3 mg/kg (ip) failed to block the analgesic effects of Cro. These results suggest that Cro has analgesic effects mediated by an action on the central nervous system. The muscarinic and opioid receptors are not involved in the antinociceptive effects of Cro.

A long-form alpha-neurotoxin from cobra venom produces potent opioid-independent analgesia1

In light of the antinociceptive activity of the short-chain neurotoxin, cobrotoxin, and other acetylcholine antagonists, the antinociceptive activity and mechanisms of cobratoxin (CTX), a long-chain postsynaptic alpha-neurotoxin, was investigated in rodent pain models. CTX was administered intraperitoneally (30, 45, 68 microg/kg), intra-cerebral ventricularly (4.5 microg/kg) or microinjected into periaqueductal gray (PAG; 4.5 microg/kg). The antinociceptive action was tested using the hot-plate and acetic acid writhing tests in mice and rats. The involvement of the cholinergic system and opioid system in CTX-induced analgesia was examined by pretreatment of animals with atropine (0.5 mg/kg, im; or 10 mg/kg, ip) or naloxone (1 and 5 mg/kg, ip). The effect of CTX on motor activity was tested using the Animex test. CTX exhibited a dose-dependent analgesic action in mice as determined by both the hot-plate and acetic acid writhing tests. The peak effect of analgesia was seen 3 h after administration. In the mouse acetic acid writhing test, the intra-cerebral ventricular administration of CTX at 4.5 microg/kg (1/12th of a systemic dose) produced marked analgesic effects. Microinjection of CTX (4.5 microg/kg) into the PAG region did not elicit an analgesic action in rats in the hot-plate test. Atropine at 0.5 mg/kg (im) and naloxone at 1 and 5 mg/kg (ip) both failed to block the analgesic effects of CTX, but atropine at 10 mg/kg (ip) did antagonize the analgesia mediated by CTX in the mouse acetic acid writhing test. Acetylsalicylic acid (300 mg/kg) did not enhance the analgesic effects of CTX. At the highest effective dose of 68 microg/kg the neurotoxin did not change the spontaneous mobility of mice. CTX has analgesic effects, which are mediated in the central nervous system though not through the PAG. The central cholinergic system but not opioid system appears to be involved in the antinociceptive action of CTX.

Evaluation of the Antinociceptive and Anti-inflammatory Activities of Satureja thymbra. L. Essential Oil

The aim of this study was to investigate the antinociceptive and anti-inflammatory activities of the essential oil of Satureja thymbra. L. (Lamiaceae). Antinociceptive activity of the essential oil was measured by the formalin test in mice and by the light tail-flick and hot-plate methods in rats. The paw-edema test was performed in rats to evaluate the anti-inflammatory effect of the essential oil. Motor coordination was assessed with a rotarod apparatus. Although the essential oil produced an antinociceptive effect during both the early (50 and 100 mg kg−1) and late phases (25, 50, and 100 mg kg−1) of the formalin test, it did not exert any significant antinociceptive and anti-inflammatory effects in tail-flick and paw-edema tests, respectively. In addition, a significant antinociceptive effect was detected in the hot-plate test (100 and 200 mg kg−1). No significant change was detected in sensory motor performance. In conclusion, S. thymbra. L. essential oil does not exert any anti-inflammatory effect while it may have central analgesic activity in mice and rats.

INVESTIGATING THE ANTI-INFLAMMATORY AND ANALGESIC ACTIVITY OF LEAVES OF WEDELIA CHINENSIS (OSBECK) MERR. IN STANDARD EXPERIMENTAL ANIMAL

The ethanolic extract of Wedelia chinensis (EEWC) belonging to the family of Asteraceae was evaluated by hot plate and acetic acid induced writhing methods to assess its analgesic activity. The extract was also evaluated for its by using on carrageenan, mediators such as histamine and serotonin induced paw oedema, and cotton pellet induced granuloma tests for its effect on acute and chronic phase inflammation models in rats, as well as analgesic activity in mice. It was found that the extract caused an inhibition on the writhing response induced by acetic acid in a dose dependent manner. Dose of 500 mg/kg EEWC and aspirin could block the writhing response by 51.92 % and 68.68 % (p < 0.001), respectively. It was also indicated that the EEWC showed significant antinociceptive action in hot plate reaction time method in mice. This effect was comparable to that of standard drug morphine treated controls, suggesting the central activity of EEWC. Maximum inhibition (56.14 %) was obtained at the dose of 500 mg/kg after 3 h of drug treatment in carrageenan induced paw oedema, whereas indomethacin (standard drug) produced 61.65 % of inhibition. In the chronic model (cotton pellet induced granuloma) the EEWC (125,250 and 500 mg/kg) and standard drug showed decreased formation of granuloma tissue by 56.69,34.57,43.30 % and 55.23 % respectively. The results indicate the potent analgesic and anti-inflammatory effects and therapeutic efficacy of Wedelia chinensis extract on animal models which are comparable with those of standard drugs such as Aspirin, Morphine and Indomethacin respectively.

Analgesic activity of Amorphophallus campanulatus tuber

The methanol extract of Amorphophallus campanulatus tuber, given orally at the doses of 250 and 500 mg/kg, showed significant analgesic activity in mice.

Novel therapeutic agents: The analgesic actions of pregabalin are mediated through its binding to the α 2-δ-1 subunit of voltage-gated calcium channels

Neuropathic pain resulting from damage to or dysfunction of the nervous system affects the lives of millions of people suffering from conditions including diabetes and postherpetic neuralgia. This severe pain is very difficult to treat, but pregabalin has proven clinical efficacy. This compound is unlike traditional analgesics, such as nonsteroidal–anti-inflammatory drugs or narcotics. It has no anti-inflammatory actions and no effect on physiologic pain. Despite extensive preclinical research, including the isolation and sequencing of the binding protein and its identification as the α2-δ subunit of voltage-gated calcium channels, proof of the importance of this auxiliary protein in the mechanism of action of pregabalin has remained elusive. Here, we show that pregabalin has reduced binding affinity and no analgesic action in mice expressing a mutated gene encoding a specific auxiliary subunit protein (α2-δ-1) of voltage-dependant calcium channels. The R217A mutant mouse has a single amino acid substitution at position 217 in the α2 protein which prevents the binding of pregabalin. The mutant demonstrates normal pain phenotypes, indistinguishable from the wild-type controls derived from the same breeding cohort. Pregabalin (30 to 100 mg/kg, s.c.) failed to block the late-phase response in the formalin test and the static allodynia induced by Chronic Constriction Injury (CCI) in the mutants but was fully active in the wild-type mice. Both wild-type and mutant mice showed typical responses to morphine (3 mg/kg, s.c.) in the formalin test and to amitriptyline (2 to 8 mg/kg, p.o.) in the CCI model. These are the first data demonstrating that the analgesic actions of pregabalin are mediated through its binding to the α2-δ-1 subunit of voltage-gated calcium channels. These data establish pregabalin as a member of a novel class of analgesic agents.

Anti-inflammatory and Analgesic Activity of Uraria lagopoides

Anti-inflammatory activity of alcohol and aqueous extract of aerial parts of Uraria lagopoides was determined in the rat paw edema test. At doses of 100 and 200 mg/kg, oral, the extract inhibited edema significantly (p < 0.01) compared with indomethacin (20 mg/kg). It also showed marked analgesic activity in mice (p < 0.01), compared with acetylsalicylic acid (100 mg/kg) in acetic acid-induced writhing test.

Antinociceptive action of Ocimum sanctum (Tulsi) in mice: possible mechanisms involved

The alcoholic leaf extract of Ocimum sanctum (OS, Tulsi) was tested for analgesic activity in mice. In the glacial acetic acid (GAA)-induced writhing test, OS (50, 100 mg/kg, i.p.; and 50, 100, 200 mg/kg, p.o.) reduced the number of writhes. OS (50, 100 mg/kg, i.p.) also increased the tail withdrawal latency in mice. Naloxone (1 mg/kg, i.p.), an opioid antagonist, and DSP-4 (50 mg/kg, i.p.), a central noradrenaline depletor, attenuated the analgesic effect of OS in both the experimental models, whereas, PCPA (300 mg/kg, i.p.), a serotonin synthesis inhibitor, potentiated the action of OS on tail flick response in mice. The results of our study suggest that the analgesic action of OS is exerted both centrally as well as peripherally and involves an interplay between various neurotransmitter systems.

N-(3-Acyloxy-2-benzylpropyl)-N‘-[4-(methylsulfonylamino)benzyl]thiourea Analogues: Novel Potent and High Affinity Antagonists and Partial Antagonists of the Vanilloid Receptor

Isosteric replacement of the phenolic hydroxyl group in potent vanilloid receptor (VR1) agonists with the alkylsulfonamido group provides a series of compounds which are effective antagonists to the action of the capsaicin on rat VR1 heterologously expressed in Chinese hamster ovary (CHO) cells. In particular, compound 61, N-[2-(3,4-dimethylbenzyl)-3-pivaloyloxypropyl]-N'-[3-fluoro-4-(methylsulfonylamino)benzyl]thiourea was a full antagonist against capsaicin, displayed a K(i) value of 7.8 nM (compared to 520 nM for capsazepine and 4 nM for 5-iodoRTX), and showed excellent analgesic activity in mice. Structure-activity analysis of the influence of modifications in the A- and C-regions of 4-methylsulfonamide ligands on VR1 agonism/antagonism indicated that 3-fluoro substitution in the A-region and a 4-tert-butylbenzyl moiety in the C-region favored antagonism, whereas a 3-methoxy group in the A-region and 3-acyloxy-2-benzylpropyl moieties in the C-region favored agonism.