Mechanisms of antinociceptive effects of ouabain in combination with neostigmine in the rat

BACKGROUND： It has been previously shown that intrathecal administration of either ouabain or neosdgmine can produce antinociceptive effects. Moreover, ouabain and neostigmine are differently associated with acetylcholine. OBJECTIVE： It has been hypothesized that intrathecal administration of ouabain, in combination with neostigmine, can produce antinociceptive synergistic effects. Atropine, as a competitive antagonist, was pre-injected to verify the mechanisms of action. DESIGN, TIME AND SETTING： This study was a randomized, controlled, animal experiment, performed at the State Key Laboratory of Oncology in Southern China between May 2006 and February 2007. MATERIALS： A total of 102 healthy, adult, Sprague Dawley rats were included. Ouabain and neostigmine （Sigma, USA）, as well as atropine （Tanabe Seiyaku, Japan）, were also used. METHODS： Varied doses of ouabain, neostigmine, and a combination of the two were intrathecally injected into rats. Six rats were allotted for each dose group. Intrathecal pretreatment with atropine was tested 10 minutes prior to intrathecal administration of neostigmine or the combination of ouabain and neostigmine. MAIN OUTCOME MEASURES： Tail-flick tests were performed to measure tail-flick latency （seconds） prior to and after administration. The response in the tail-flick test was expressed as the percentage of maximum possible effect （% MPE）, where % MPE = [tail-flick latency after administration （seconds） -mean baseline value for tail-flick latency]/[ 10 seconds - the mean baseline value for tail-flick latency （seconds）] x 100%. RESULTS： Rat spinal intrathecal administration of either ouabain or neostigmine alone produced antinociceptive effects in a dose-dependent manner. Intrathecally administration of neostigmine （0.05, 0.1, 0.3 μg ） in combination with ouabain （1 μ g ） produced enhanced antinociceptive effects, with a % MPE of 29%, 78%, and 95%, respectively （P 〈 0.05）. Intrathecally administration of 0.3μg neostigmine （% MPE： 45%）, in combination with 1 μ g ouabain （% MPE： 27%） produced potent antinociceptive effects （% MPE： 95%）. Intrathecally pre-injected atropine antagonized the antinociceptive effects of neostigmine （3 μg）, or a combination of ouabain （1 μg） and neostigmine （0.3 μg） （P 〈 0.01）. CONCLUSION： Rat spinal intrathecal administration of either ouabain or neostigmine alone produced dose-dependent andnociceptive effects. Ouabain enhanced the antinociceptive effects of neostigmine. Atropine antagonized the antinociceptive effects of neostigmine or the combination of ouabain and neostigmine. This occurs possibly due to the fact that atropine is a competitive antagonist of the muscarinic acetylcboline receptors.

Pentapeptide Any-GS Blocks Antinociceptive Effect of Poneratoxin in Rats

Poneratoxin （PoTX） is an insect neuropeptide isolated from ant venom. It was previously demonstrated that administration of synthetic PoTX into the lateral brain ventricle （icv） induced in rats significant antinociceptive effect. Moreover it was demonstrated that this effect was not mediated by opioid receptors. The aim of present study was to determine other probable mechanisms mediating antinociceptive effect of PoTX, above all： （1） to check if insect-derived pentapeptide Any-GS may influence on PoTX-induced analgesia in rats, and （2） to estimate the role of voltage-gated sodium channels in rat＇s brain in antinociceptive effect of PoTX. The study was performed on adult, female wistar rats, which a week before experiments were implanted with polyethylene cannulas into the lateral brain ventricle （icv）. Antinociceptive effect of PoTX applied directly icv was determined in rats by the test of the tail immersion. PoTX applied icv at the dose of 1 or 5 nmol induced significant antinociceptive effect in rats. Pretreatment rats with equimolar dose of 1 or 5 nmol of veratridine, an agent, which opens voltage-gated sodium channels in neurons of rat brain, did not modify effect of PoTX. On the other hand, prior icv administration of pentapeptide Any-GS significantly inhibited antinociceptive effect of both icv doses of 1 and 5 nmols of PoTX. The results of the present study demonstrated antagonistic effect Any-GS against PoTX-induced analgesia. Thus blocking effect Any-GS on PoTX-induced analgesia indicates that this insect peptide is a probable antagonist of PoTX.

Comparative study of chemical composition, antinociceptive effect and acute toxicity of the essential oils of three Asarum drugs

In the present study, the chemical composition, antinociceptive effect and acute toxicity of essential oils（EOs） of Asarum heterotropoides Fr. Schmidt var. mandshuricum（Maxim.） Kitag.（AHM）, A. sieboldii Miq. var. seoulense Nakai（ASS） and A. himalaicum Hook. f. et Thoms. ex Klotzsch.（AH） were comparatively evaluated. A total of 55 compounds were identified in EOs of AHM, ASS and AH by GC-MS. Methyleugenol（20.16%–62.89%）, safrole（2.67%–32.42%）, 3,5-dimethoxytoluene（2.00%–18.59%） and eucarvone（1.52%–19.16%） were the major constituents of EO of AHM, and methyleugenol（48.35%–61.06%）, eucarvone（11.13%–13.93%） and elemicin（4.79%–11.14%） were the major constituents of EO of ASS. The EO of AH was different from that of AHM and ASS, in which patchouli alcohol（27.42%–51.95%） and elemicin（13.11%–42.23%） were found in a greater amount. Moreover, the antinociceptive effect of EOs of AHM（5.5, 11.0, 16.5 μL/kg） and AH（2.0, 4.0, 6.0 μL/kg） was comparatively assayed in acetic acid-induced writhing, hot plate and formalin tests. The results indicated a weak central, but potent peripheral antinociceptive effect of EO of AHM, and more potent central and peripheral antinociceptive effect of EO of AH. The LD50 of the EOs of AHM and AH were 1.7 and 7.7 mL/kg, respectively. These findings suggest that EOs of AHM and AH possess evident antinociceptive activity and are probably safe within the range of its clinical doses. However, their chemical compositions are quite different. Therefore, AH can be clinically used as an herbal medicinal product with broad analgesic effects, but should not be confused with AHM and ASS used in traditional Chinese medicine.

Effect of Synthetic Leucopyrokinin Analog [D-AlaS]-[2-8]-Leucopyrokinin （[D-AlaS]-[2-8]-LPK） on Opioid-lnduced Analgesia in Rats

The study was undertaken in order to evaluate effect of synthetic insect neuropeptide leucopyrokinin analog, [D-Ala5]-[2-8]-LPK, on analgesia induced by selective agonists of/a-, 6- and l〈-opioid receptors. The study was performed on male Wistar rats, which a week before the experiments were implanted with polyethylene cannulas into the lateral brain ventricle （icv）. Effect of prior administration of [D-Ala5]-[2-8]-LPK on analgesia induced in rats by next icv administration of equimolar dose of μ-, δ- and -opioid agonists： DAMGO, DPDPE and GR fumarate respectively, was evaluated. Antinociceptive effect was determined in rats by the test of the tail immersion. It was found that two doses of 5 and 10 nmols icv of [D-AlaS]-[2-8]-LPK inhibited analgesia in rats by equimolar doses of DAMGO. This analog also transiently （only in two time intervals） and in one dose of 10 nmols inhibited analgesia induced in rats by icv administration of equimolar DPDPE dose of 10 nmols icv. Obtained results indicate that [D-AlaS]-[2-8]-LPK inhibits antinociceptive effect of DAMGO and in part of DPDPE, i.e. mainly antagonized ~t-opioid receptors. These results correspond with results of our previous study that selective antagonists of μ- and δ-opioid receptors blocked antinociceptive effect of synthetic insect neuropeptide leucopyrokinin and of it active analog [2-8]-leucopyrokinin. We regard that [D-AIaS]-[2-8]-LPK, the first discovered antagonist of leucopyrokinin may be a useful as a probable tool substance in the study of biological effects of insect-derived peptides either in invertebrates or in mammals.

The Effect of Tramadol on Blood Glucose Levels in Rats

The Background: Tramadol, is a central acting analgesic that possesses weak affinity for the μ-opioid receptor and modifies transmission of nociceptive impulses through inhibition of monoamine reuptake. This study was designed to determine the effect of tramadol on blood glucose levels and also to investigate whether or not alpha-2 adrenergic receptors were responsible for this effect. Methods: Twenty-five Wistar male rats were assigned to four groups to receive: Group I: saline;Group II: tramadol (1 mg·kg-1);Group III and Group IV: pretreatment with a2-receptor antagonist drugs yohimbine (1 mg·kg-1) or idazoxan (1 mg·kg-1), 30 min before administration of tramadol (1 mg·kg-1). Samples for plasma glucose measurement were withdrawn at 0, 30, 60, 90 and 120 minutes of the experiment. Results: A significant rise in blood glucose levels was observed following administration of i.v. tramadol. Pretreatment with both yohimbine and idazoxan (1 mg·kg-1) significantly attenuated tramadol-induced hyperglycemia. Conclusion: The results of the study indicate that, tramadol administered at an analgesic dose of 1 mg·kg-1 produces hyperglycemia in diethyl ether anesthetized rats. Reversal of this effect with a2-adrenoceptor blocking agents suggests that monoaminergic pathways which contribute to the analgesic action of tramadol, may have a role in the hyperglycemic action of the drug.

Combinative Approaches of Chemistry, Pharmacology and Toxicology for the Optimal Pharmaceutical Preparation of an Anti-arthritic Chinese Medicine Formulation QFJBT

Objective Qing Fu Juan Bi Tang(QFJBT)is an anti-arthritic Chinese medicine formula consisting of five herbs:Aconiti Lateralis Radix Praeparata(Fu Zi,附子),Sinomenii Caulis(Qing Feng Teng,青风藤),Astragali Radix(Huang Qi,黄芪),Paeoniae Radix Alba(Bai Shao,白芍)and Moutan Cortex(Mu Dan Pi,牡丹皮),which have well-established histories of use for treatment of rheumatic and arthritic diseases.We intended to establish the optimized and standardized pharmaceutical procedures and manufacturing processes for the pilot production of QFJBT to develop it as a novel botanical drug product for treatment of rheumatoid arthritis(RA).Methods The combinative approaches of chemical assessment,toxicological and pharmacological evaluation were explored to define the pharmaceutical preparation of QFJBT.Results The optimized and standardized pharmaceutical procedures and manufacturing processes for the pilot production of QFJBT were established in terms of greatest chemical contents of bioactive constituents,potent anti-inflammatory and antinociceptive activities,and favorable safety profile.Quality analysis of the pilot product of QFJBT by high-performance liquid chromatography(HPLC)demonstrated that the chromatographic fingerprint profiles of three batches of QFJBT were basically identical and the contents of four characteristic and bioactive markers were relatively consistent.General toxicological studies showed a favorable safety profile of QFJBT.The maximum tolerated single dose of QFJBT was determined in both sexes of rats to be 33.63 g/kg body weight which is equivalent to 346 times of clinical dose.In the chronic oral toxicity study,the results of laboratory investigation showed that QFJBT at doses of 3.89,6.80 and 9.72 g/kg body weight(equivalent to 40,70 and 100-fold clinical doses,respectively)caused no changes in all hematological parameters and blood biochemical parameters of rats.No mortality or specific toxic responses were observed in animals after three months of repeated dosing with QFJBT.Conclusion The optimized and standardized pharmaceutical and manufacturing processes for the production of QFJBT have been successfully screened and identified through established rigorous in-process controls.