Two new nontoxic, non-pathogenic strains of Sphingomonas elodea for gellan gum production.

Two new strains of Sphingomonas elodea (designated as PHP1 and PBAD1) were tested for toxicity and pathogenicity in healthy Sprague-Dawley CD(®) IGS rats in separate studies. In each study, twelve rats/sex were administered ≥10(8) viable cells/rat by oral gavage, and four untreated rats/sex served as controls. Blood, feces, and selected organs/tissues collected at various times over the course of the 22 day study were evaluated for the presence of PHP1 or PBAD1 (depending on the study) by a validated method, to determine the potential for survival, propagation, or infectivity of PHP1 and PBAD1 cells in the rat. No mortalities, test substance-related changes in clinical or macroscopic findings, body weight or body weight gain were observed in treated animals compared with controls, indicating a lack of toxicity. PHP1 or PBAD1 were not detected in the tissue, fecal or fluid samples collected from treated animals. Therefore, neither PHP1 nor PBAD1 were pathogenic or acutely toxic under the conditions of the studies.

Robustness of arterial blood gas analysis for assessment of respiratory safety pharmacology in rats.

Whole body plethysmography using unrestrained animals is a common technique for assessing the respiratory risk of new drugs in safety pharmacology studies in rats. However, wide variations in experimental technique make cross laboratory comparison of data difficult and raise concerns that non-appropriate conditions may mask the deleterious effects of test compounds - in particular with suspected respiratory depressants. Therefore, the objective of this study was to evaluate the robustness of arterial blood gas analysis as an alternative to plethysmography in rats. We sought to do this by assessing the effect of different vehicles and times post-surgical catheterization on blood gas measurements, in addition to determining sensitivity to multiple opioids. Furthermore, we determined intra-lab variability from multiple datasets utilizing morphine and generated within a single lab and lastly, inter-lab variability was measured by comparing datasets generated in two separate labs. Overall, our data show that arterial blood gas analysis is a measure that is both flexible in terms of experimental conditions and highly sensitive to respiratory depressants, two key limitations when using plethysmography. As such, our data strongly advocate the adoption of arterial blood gas analysis as an investigative approach to reliably examine the respiratory depressant effects of opioids.

In vivo characterization of a dual adenosine A2A/A1 receptor antagonist in animal models of Parkinson's disease.

The in vivo characterization of a dual adenosine A(2A)/A(1) receptor antagonist in several animal models of Parkinson's disease is described. Discovery and scale-up syntheses of compound 1 are described in detail, highlighting optimization steps that increased the overall yield of 1 from 10.0% to 30.5%. Compound 1 is a potent A(2A)/A(1) receptor antagonist in vitro (A(2A) K(i) = 4.1 nM; A(1) K(i) = 17.0 nM) that has excellent activity, after oral administration, across a number of animal models of Parkinson's disease including mouse and rat models of haloperidol-induced catalepsy, mouse model of reserpine-induced akinesia, rat 6-hydroxydopamine (6-OHDA) lesion model of drug-induced rotation, and MPTP-treated non-human primate model.

Plant-derived polysaccharide supplements inhibit dextran sulfate sodium-induced colitis in the rat.

Several plant-derived polysaccharides have been shown to have anti-inflammatory activity in animal models. Ambrotose complex and Advanced Ambrotose are dietary supplements that include aloe vera gel, arabinogalactan, fucoidan, and rice starch, all of which have shown such activity. This study was designed to evaluate these formulations against dextran sulfate sodium (DSS)-induced colitis in rats and to confirm their short-term safety after 14 days of daily dosing. Rats were dosed daily orally with vehicle, Ambrotose or Advanced Ambrotose. On day six groups of rats received tap water or 5% Dextran Sulfate sodium. Ambrotose and Advanced Ambrotose significantly lowered the disease scores and partially prevented the shortening of colon length. An increase in monocyte count was induced by dextran sulfate sodium and inhibited by Ambrotose and Advanced Ambrotose. There were no observable adverse effects after 14-day daily doses. The mechanism of action of the formulations against DSS-induced colitis may be related to its effect on monocyte count.

N,N-Diethyl-4-[(3-hydroxyphenyl)(piperidin-4-yl)amino] benzamide derivatives: the development of diaryl amino piperidines as potent delta opioid receptor agonists with in vivo anti-nociceptive activity in rodent models.

We have investigated a series of phenolic diaryl amino piperidine delta opioid receptor agonists, establishing the importance of the phenol functional group and substitution on the piperdine nitrogen for delta agonist activity and selectivity versus the mu and kappa opioid receptors. This study uncovered compounds with improved agonist potency and selectivity compared to the standard, non-peptidic delta agonist SNC-80. In vivo anti-nociceptive activity of analog 8e in two rodent models is discussed, demonstrating the potential of delta agonists to provide a novel mechanism for pain relief.

Rapid and sensitive determination of acetylsalicylic acid and salicylic acid in plasma using liquid chromatography-tandem mass spectrometry: application to pharmacokinetic study.

A simple and sensitive analytical method using liquid chromatography-tandem mass spectrometry (LC/MS/MS) for determination of acetylsalicylic acid (aspirin, ASA) and its major metabolite, salicylic acid (SA), in animal plasma has been developed and validated. Both ASA and SA in plasma samples containing potassium fluoride were extracted using acetonitrile (protein precipitation) with 0.1% formic acid in it. 6-Methoxysalicylic acid was used as the internal standard (IS). The compounds were separated on a reversed-phase column. The multiple reaction monitoring mode was used with ion transitions of m/z 178.9 --> 136.8, 137.0 --> 93.0 and 167.0 --> 123.0 for ASA, SA and IS, respectively. The lower limits of quantification for ASA and SA were 3 and 30 ng/mL, respectively. The developed method was successfully applied for the evaluation of pharmacokinetics of ASA and SA after p.o. and i.v. administration of 1 mg/kg to rats.

Anti-obesity, anti-diabetic, and lipid lowering effects of the thyroid receptor beta subtype selective agonist KB-141.

Selective thyroid hormone receptor subtype-beta (TRbeta) agonists have received attention as potential treatments for hypercholesterolemia and obesity, but have received less attention as treatments for diabetes, partly because this condition is not improved in thyroid hormone excess states. The TRbeta selective agonist KB-141 induces 5-10% increases in metabolic rate and lowering of plasma cholesterol levels without tachycardia in lean rats, unlike the major active thyroid hormone, T3. In the current study, we determined whether KB-141 promotes weight loss in obese animals and whether it exhibits anti-diabetogenic effects. Body weight, adiposity (DEXA), and lipid levels were examined following p.o. administration of KB-141 to obese Zucker fa/fa rats at 0.00547-0.547 mg/kg/day for 21 days, and in ob/ob mice at 0.5mg/kg/day KB-141 for 7 days. In rats, KB-141 reduced body weight by 6 and 8%, respectively, at 0.167 and 0.0547 mg/kg/day without tachycardia and adiposity was reduced at 0.167 mg/kg/day (5-6%). In ob/ob mice, KB-141 lowered serum cholesterol (35%), triacylglycerols (35%) and both serum and hepatic free fatty acids (18-20%) without tachycardia. Treatment of ob/ob mice with KB-141 (0.0547 or 0.328 mg/kg/day over 2 weeks) improved glucose tolerance and insulin sensitivity in a dose-dependent manner with no effect on heart rate. Thus, KB-141 elicits anti-obesity, lipid lowering and anti-diabetic effects without tachycardia suggesting that selective TRbeta activation may be useful strategy to attenuate features of the metabolic syndrome.

Pharmacological profile of the thyroid hormone receptor antagonist NH3 in rats.

NH3 is a thyroid hormone receptor (TR) antagonist that inhibits binding of thyroid hormones to their receptor and that inhibits cofactor recruitment. It was active in a tadpole tail resorption assay, with partial agonist activity at high concentrations. We determined the effect of NH3 on the cholesterol-lowering, thyroid stimulating hormone (TSH)-lowering, and tachycardic action of thyroid hormone (T(3)) in rats. Cholesterol-fed, euthyroid rats were treated for 7 days with NH3, and a dose response (46.2-27,700 nmol/kg/day) was determined. We also determined the effect of two doses of T(3) on the NH3 dose-response curve. NH3 decreased heart rate modestly starting at 46.2 nmol/kg/day, but the effect was lost at >2920 nmol/kg/day. At 27,700 nmol/kg/day, tachycardia was seen, suggesting partial agonist activity. NH3 increased plasma cholesterol to a maximum of 27% at 462 nmol/kg/day. At higher doses, cholesterol was reduced, suggesting partial agonist activity. Plasma TSH was increased from 46.2 to 462 nmol/kg/day NH3, but at higher doses, this effect was lost, and partial agonist effects were apparent. T(3) at 15.4 and 46.2 nmol/kg/day increased heart rate, reduced cholesterol, and reduced plasma TSH. NH3 inhibited the cholesterol-lowering, TSH-lowering and tachycardic effects of 15.4 nmol/kg/day T(3), but much of the effect was lost at >924 nmol/kg/day doses. NH3 had no effect on the cholesterol-lowering action of 46.2 nmol/kg/day T(3), but it inhibited the tachycardic and TSH suppressant effects up to the 924 nmol/kg/day dose. Single doses of 462 and 27,700 nmol/kg caused no TR inhibitory effects. In conclusion, NH3 has TR antagonist properties on T(3)-responsive parameters, but it has partial agonist properties at higher doses.

Neuropathy-induced osteopenia in rats is not due to a reduction in weight born on the affected limb.

Changes in bone mineral density (BMD) are associated with clinical neuropathies. Following nerve injury in the rat, there is a loss of BMD, which may be related to nerve injury or reduced mechanical loading. The purpose of this study was to investigate if altered mechanical loading is solely responsible for the observed loss of BMD in neuropathic pain models. In addition, we sought to study the action of chronic bisphosphonate treatment on both neuropathy-induced osteopenia and pain. We therefore had two hypotheses: firstly, that nerve injuries can have variable effects on hind limb bone loss in rats which are not attributable to differences in the extent of hind limb disuse and, secondly, that bisphosphonate treatment can reverse bone loss in a rat mononeuropathy model, and this is not attributable to bisphosphonate effects on nociception or hind paw unweighting. Male Sprague-Dawley rats were subject to chronic constriction injury (CCI), partial sciatic nerve ligation (PSN) or L5 + L6 spinal nerve ligation (SNL). Loss of BMD, defined as a numerically lower BMD as compared to control animals, was extreme following CCI (maximum ipsilateral/contralateral difference of 0.023 +/- 0.011); BMD loss following either PSN or SNL in the rat was subtle (0.010 +/- 0.002 and 0.013 +/- 0.012 g/cm2, respectively), significant only at early time points and had resolved by 7 weeks post-surgery. Chronic bisphosphonate treatment significantly inhibited CCI-induced osteopenia in the rat without inhibiting the reduction in weight-bearing tactile allodynia or mechanical hyperalgesia. Loss of BMD is observed in rats in a variety of neuropathic pain models. Lack of correlation between neuropathy-induced bone loss and weight bearing demonstrates that the bone loss is not simply a function of reduced mechanical loading and suggests that altered bone-nerve signaling is involved. Furthermore, chronic bisphosphonate treatment inhibits neuropathy-induced osteopenia without affecting behavioral measurements of neuropathic pain. This indicates that osteopenia is not directly related to neuropathic pain behaviors.

A role for cannabinoid receptors, but not endogenous opioids, in the antinociceptive activity of the CB2-selective agonist, GW405833.

Several recent reports have demonstrated a role for selective cannabinoid CB2 receptor agonists in pain modulation, showing both analgesic and antihyperalgesic activities. While the mechanism of action is poorly understood, it has been postulated that these effects may be indirect, involving release of endogenous opioids. We have previously reported that administration of the selective cannabinoid CB2 receptor agonist GW405833 (2,3-dichloro-phenyl)-[5-methoxy-2-methyl-3-(2-morpholin-4-yl-ethyl)-indol-1-yl]-methanone) to rats elicits potent and efficacious antihyperalgesic effects against neuropathic and inflammatory pain and, at high dose (100 mg/kg), is analgesic and ataxic [Valenzano, K.J., Tafesse, L., Lee, G., Harrison, J.E., Boulet, J., Gottshall, S.L., Mark, L., Pearson, M.S., Miller, W., Shan, S., Rabadi, L., Rotstheyn, Y., Chaffer, S.M., Turchin, P.I., Elsemore, D.A., Toth, M., Koetzner, L., Whiteside, G.T., 2005. Pharmacological and pharmacokinetic characterization of the cannabinoid receptor 2 agonist, GW405833, utilizing rodent models of acute and chronic pain, anxiety, ataxia and catalepsy. Neuropharmacology 48, 658-672]. In the current study, we confirm these properties using mouse models and investigate the role of cannabinoid CB2 receptors using knockout animals. Furthermore, we provide evidence that the antinociceptive properties of GW405833 are opioid independent. GW405833 elicited robust antihyperalgesic effects in mouse models of inflammatory (Freund's complete adjuvant) and neuropathic (Seltzer) pain. In contrast, GW405833 showed no antihyperalgesic activity against Freund's complete adjuvant-mediated inflammatory pain in cannabinoid CB2 receptor knockout mice. As in rats, high-dose GW405833 (100 mg/kg) showed both analgesic and sedative activities in wild-type mice, activities that were also apparent in cannabinoid CB2 receptor knockout mice. In rats, neither the antihyperalgesic effect in the Freund's complete adjuvant model nor the analgesic effects in tail flick and hot plate assays were inhibited by pre-treatment with the non-selective opioid receptor antagonist, naltrexone. These data demonstrate that the antihyperalgesic effects of GW405833 are mediated via the cannabinoid CB2 receptor, whereas the analgesic and sedative effects are not. Furthermore, these data suggest that the mechanism of action for GW405833 does not depend on the release of endogenous opioids.

The role of central and peripheral mu opioid receptors in inflammatory pain and edema: a study using morphine and DiPOA ([8-(3,3-diphenyl-propyl)-4-oxo-1-phenyl-1,3,8-triaza-spiro[4.5]dec-3-yl]-acetic acid).

The role of opioid receptors located in the central nervous system (CNS) and peripheral nervous system in inflammatory pain is well established. In contrast, although it is has been shown that mu agonists can reduce other manifestations of inflammation, such as edema, the mechanism of action remains unclear. In this study, we have activated mu receptors located centrally, those located peripherally, and those located both centrally and peripherally and compared the effects on pain and edema using the rat carrageenan model of acute inflammation. Activation of mu receptors located only in the periphery, by administration of the peripheralized mu agonist [8-(3,3-diphenyl-propyl)-4-oxo-1-phenyl-1,3,8-triaza-spiro[4.5]dec-3-yl]-acetic acid (DiPOA) or local administration of morphine, resulted in antihyperalgesia (30 mg/kg DiPOA, 83% inhibition; 100 microg/rat morphine, 75% inhibition) without affecting edema. In contrast, activation of both central and peripheral mu receptors using systemically administered morphine resulted in antihyperalgesia (1 mg/kg, 80% inhibition) and inhibition of edema (10 mg/kg, 54% inhibition). Finally, activation of only receptors located in the CNS, by central administration of DiPOA or systemic administration of morphine after block of only the peripheral mu receptors using q-naltrexone, resulted in a significant reduction in edema. Our findings confirm the role of peripheral mu receptors in the pathology of pain associated with acute inflammation and argue against the involvement of these receptors in edema formation. Furthermore, our data demonstrate that activation of mu receptors in the brain inhibits carrageenan-induced edema and suggest that the antiedematous effect of morphine is due to action at central receptors alone.

Pharmacological and pharmacokinetic characterization of the cannabinoid receptor 2 agonist, GW405833, utilizing rodent models of acute and chronic pain, anxiety, ataxia and catalepsy.

To date, two cannabinoid receptors have been identified, CB1 and CB2. Activation of these receptors with non-selective cannabinoid receptor agonists reduces pain sensitivity in animals and humans. However, activation of CB1 receptors is also associated with central side effects, including ataxia and catalepsy. More recently, a role for selective CB2 agonists in pain modification has been demonstrated. GW405833, a selective CB2 agonist, was recently reported to partially reverse the inflammation and hyperalgesia in a rat model of acute inflammation. In the current report, we extend the characterization and therapeutic potential of this compound. For the first time, we show that GW405833 selectively binds both rat and human CB2 receptors with high affinity, where it acts as a partial agonist (approximately 50% reduction of forskolin-mediated cAMP production compared to the full cannabinoid agonist, CP55,940). We also report for the first time that intraperitoneal administration of GW405833 (0.3-100 mg/kg) to rats shows linear, dose-dependent increases in plasma levels and substantial penetration into the central nervous system. In addition, GW405833 (up to 30 mg/kg) elicits potent and efficacious antihyperalgesic effects in rodent models of neuropathic, incisional and chronic inflammatory pain, the first description of this compound in these models. In contrast, analgesia, sedation and catalepsy were not observed in this dose range, but were apparent at 100 mg/kg. Additionally, GW405833 was not antihyperalgesic against chronic inflammatory pain in CB2 knockout mice. These data support the tenet that selective CB2 receptor agonists have the potential to treat pain without eliciting the centrally-mediated side effects associated with non-selective cannabinoid agonists, and highlight the utility of GW405833 for the investigation of CB2 physiology.

Development and pharmacological characterization of a rat model of osteoarthritis pain.

Osteoarthritis (OA) is an age-related joint disease characterized by degeneration of articular cartilage and is associated with chronic pain. Although several experimental models of OA have been employed to investigate the underlying etiologies of the disease, there has been relatively little investigation into development of animal models of OA to study the pain associated with the condition. In the present study, we investigated OA induced by injection of either iodoacetate or papain into the knee joint of rats, and assessed the joint degeneration with radiographic analyses and measured pain behavior using hind limb weight bearing. We found that injection of iodoacetate, but not papain, resulted in a chronic joint degeneration as measured by decreased bone mineral content and bone mineral density, necrosis of articular cartilage and osteophyte formation. These pathological changes were associated with pain that manifested as time- and concentration-dependent alterations in hind limb weight bearing. These alterations in hind limb weight bearing were reversed with morphine, but were not significantly affected by acute administration of either indomethacin or celecoxib. However, administration of 30 mg/kg celecoxib twice daily for 10 days resulted in a significant restoration of hind limb weight bearing. We conclude that the iodoacetate model of OA is a relevant animal model to study pain associated with OA, and can be used to test potential therapeutic agents.

Pharmacological characterisation of a rat model of incisional pain.

1. Both clinical and preclinical models of postsurgical pain are being used more frequently in the early evaluation of new chemical entities. In order to assess the validity and reliability of a rat model of postincisional pain, the effects of different classes of clinically effective analgesic drugs were evaluated against multiple behavioural end points. 2. Following surgical incision, under general anaesthesia, of the plantar surface of the rat hind paw, we determined the time course of mechanical hyperalgesia, tactile allodynia and hind limb weight bearing using the Randall-Selitto (paw pressure) assay, electronic von Frey and dual channel weight averager, respectively. Behavioural evaluations began 24 h following surgery, and were continued for 9-14 days. 3. Mechanical hyperalgesia, tactile allodynia and a decrease in weight bearing were present on the affected limb within 1 day of surgery with maximum sensitivity 1-3 days postsurgery. Accordingly, we examined the effect of nonsteroidal antiinflammatory drugs (NSAIDs), morphine and gabapentin, on established hyperalgesia and allodynia, 1 day following plantar incision.4. In accordance with previous reports, both systemic morphine and gabapentin administration reversed mechanical hyperalgesia and tactile allodynia in the incised rat hind paw. Both drugs were more potent against mechanical hyperalgesia than tactile allodynia. 5. All of the NSAIDs tested, including cyclooxygenase 2 selective inhibitors, reversed mechanical hyperalgesia and tactile allodynia in the incised rat hind paw. The rank order of potency for both hyperalgesia and allodynia was indomethacin > celecoxib > etoricoxib > naproxen. 6. We have investigated the potency and efficacy of different classes of analgesic drugs in a rat model of postincisional pain. The rank order of potency for these drugs reflects their utility in treating postoperative pain in the clinic. As these compounds showed reliable efficacy across two different behavioural end points, the Randall-Selitto (paw pressure) assay and electronic von Frey, these methods may prove useful in the study of postsurgical pain and the assessment of novel treatments.