Recommendation for severity assessment following liver resection and liver transplantation in rats: Part I.

Score sheets were first introduced 30 years ago to assess pain, distress and suffering in animals. To date, however, there is still no general agreement on their use in research practice, and only a few publications can be found on this topic. In the present work, we demonstrate the use of a special score sheet for severity assessment in the first three postoperative days in two showcased studies performed on Wistar and Lewis rats undergoing liver resection or orthotopic liver transplantation, respectively. Scoring of different criteria and the total score were evaluated within each intervention. Additionally, both procedures were compared regarding their degree of severity. Suitability of these score sheets was evaluated for assessing severity of the procedures and these showed a minor severity within each investigated study. A comparison of both studies showed slightly higher scores involving liver transplantation. In contradiction to the common classification of these procedures as a moderate severity grade the score sheets applied here indicates a minor severity grade within each investigated study. Also, limitations and possible improvements in the design of our score sheets for defined interventions are reconsidered.

Severity assessment in rabbits after partial hepatectomy: Part II.

Although the recognition of pain, distress and discomfort has already been described in 1985 by Morton and Griffiths there is still very little known about the establishment of score sheets especially, regarding post-surgical pain and severity assessment for laboratory animals such as rabbits. In this paper we describe the estimation of severity and recovery status of 36 female New Zealand White rabbits (NZW) in a standardized liver resection model using two different adhesive treatments and one control group. Welfare was assessed at 3-4 consecutive days after surgery using a scoring system which included the following criteria: body weight, general state, clinical results, spontaneous behavior and clinical examination. Values could range from 0 to 20 where increasing values indicated increasing severity with a predefined humane endpoint for a score ≥20 points. Documented score points were almost exclusively a result of body weight loss, whereas clinical signs and general health status had no influence on the overall sum of points scored. Behavioral variation was solely observed postoperatively, within the first 24 h, with an average score ≤1. In contrast to the classification of a laparotomy as a moderate procedure in the EU Directive 2010/63 (annex VIII) the assessment herein presented showed a mild burden in all groups according to the scoring system used. The partial hepatectomy itself, as well as the adhesive treatment using either synthetic glue VIVO-107 or fibrin glue, were well tolerated.

[Tapentadol: with two mechanisms of action in one molecule effective against nociceptive and neuropathic pain. Preclinical overview]. / Tapentadol: mit zwei Mechanismen in einem Molekül wirksam gegen nozizeptive und neuropathische Schmerzen. Präklinischer Überblick.

Tapentadol (3-[(1R, 2R)-3-(dimethylamino)-1-ethyl-2-methylpropyl] phenol) is a centrally acting analgesic of a new substance class for the treatment of severe nociceptive and neuropathic pain. Tapentadol combines µ-opioid receptor (MOR) agonism and noradrenaline reuptake inhibition (NRI) in one molecule. Because of the combined mechanisms of action tapentadol offers a broad therapeutic spectrum for nociceptive as well as neuropathic pain. In different animal models its high efficacy was shown in acute nociceptive, acute and chronic inflammatory as well as in chronic neuropathic pain. Using several preclinical approaches it was shown that the noradrenergic component of tapentadol interacts with the opioid component and that both synergistically contribute to the analgesic effect of the substance. In comparison to known drugs with only one of the two modes of action, tapentadol, despite its high potency, has an improved tolerability profile in the relevant animal models, particularly with regard to gastrointestinal and central side effects. Tapentadol acts directly without metabolic activation and without formation of analgesically relevant metabolites. In different interaction studies a low potential for interactions was shown, thus clinically relevant drug-drug interactions are unlikely. Overall, tapentadol provides a safe pharmacodynamic-pharmacokinetic profile.

In vitro and in vivo characterization of tapentadol metabolites.

Tapentadol is a novel, centrally acting analgesic combining micro-opioid receptor (MOR) agonism and noradrenaline (NA) reuptake inhibition in a single molecule. Many classic opioids form active metabolites that contribute to analgesia and/or side effects, and the involved cytochrome P450 enzyme complex can give rise to pharmacokinetic drug-drug interactions and variability in drug efficacy due to enzyme polymorphisms. Here we report on the relevance of tapentadol metabolites. Nine metabolites, including the major metabolite tapentadol-O-glucuronide, had no analgesic effects in the tail-flick test in mice. In the phenylquinone writhing test in mice, only 5 of these metabolites showed analgesic effects. The absence or presence of analgesia correlated with moderate activity (0.5 microM < K(i) < 1.1 microM) at the NA transporter or MOR. However, the systemic exposure for these metabolites found in humans after therapeutic oral doses of tapentadol was far below their respective K(i) values at these binding sites (by a factor of > 45). Thus, it is highly unlikely that tapentadol forms metabolites that contribute in any relevant degree to its analgesic activity.

Characterisation of tumour vasculature in mouse brain by USPIO contrast-enhanced MRI.

To enhance the success rate of antiangiogenic therapies in the clinic, it is crucial to identify parameters for tumour angiogenesis that can predict response to these therapies. In brain tumours, one such parameter is vascular leakage, which is a response to tumour-derived vascular endothelial growth factor-A and can be measured by Gadolinium-DTPA (Gd-DTPA)-enhanced magnetic resonance imaging (MRI). However, as vascular permeability and angiogenesis are not strictly coupled, tumour blood volume may be another potentially important parameter. In this study, contrast-enhanced MR imaging was performed in three orthotopic mouse models for human brain tumours (angiogenic melanoma metastases and E34 and U87 human glioma xenografts) using both Gd-DTPA to detect vascular leakage and ultrasmall iron oxide particles (USPIO) to measure blood volume. Pixel-by-pixel maps of the enhancement in the transverse relaxation rates (Delta R(2) and Delta R(2)(*)) after injection of USPIO provided an index proportional to the blood volume of the microvasculature and macrovasculature, respectively, for each tumour. The melanoma metastases were characterised by a blood volume and vessel leakage higher than both glioma xenografts. The U87 glioblastoma xenografts displayed higher permeability and blood volume in the rim than in the core. The E34 glioma xenografts were characterised by a relatively high blood volume, accompanied by only a moderate blood-brain barrier disruption. Delineation of the tumour was best assessed on post-USPIO gradient-echo images. These findings suggest that contrast-enhanced MR imaging using USPIOs and, in particular, Delta R(2) and Delta R(2)(*) quantitation, provides important additional information about tumour vasculature.

Diazabicyclononanones, a potent class of kappa opioid analgesics.

The 1,5-dimethyl 3,7-diaza-3,7-dimethyl-9-oxo-2,4-di-2-pyridine-bicyclo[3.3.1]nonane-1,5-dicarboxylate, HZ2, has a high and selective affinity for the kappa opioid receptor and an antinociceptive activity comparable to morphine. In addition, it is characterized by a long duration of action and a high oral bioavailability. QSAR studies within series of kappa agonists revealed a chair-boat conformation of a double protonated HZ2 characterized by an almost parallel orientation of the C9 carbonyl group and the N7-H group and at least one aromatic ring to be the pharmacophoric arrangement. Structural variations showed that the pyridine rings in 2 and 4 position can be replaced with p-methoxy-, m-hydroxy- and m-fluoro-substituted phenyl rings. However, all other substituents have to be kept the same for a high affinity to the kappa receptor.

Synthesis and opioid receptor affinity of a series of 2, 4-diaryl-substituted 3,7-diazabicylononanones.

3,7-Diazabicyclo[3.3.1]nonan-9-ones having aryl rings in positions 2 and 4 with systematically varied substituents were synthesized using a double Mannich procedure. Radioligand binding assays were performed to measure the affinity of the compounds to the mu-, delta-, and kappa-opioid receptors. The affinity of all 2, 4-diphenyl-substituted 3,7-diazabicyclo[3.3.1]nonan-9-ones to the mu- and delta-receptors was found to be low. In contrast, with exception of the nitro- and cyanophenyl-substituted compounds, most of the diazabicycles showed considerable affinity for the kappa-receptor. In particular, the m-fluoro-, p-methoxy-, and m-hydroxy-substituted compounds have an affinity in the submicromolar range. Due to solubility problems in aqueous media, salts of HZ2 were synthesized. The methiodide shows high kappa-affinity and may, thus, be a promising candidate for development of a peripheral kappa-agonist, e.g. for use in the case of rheumatoid arthritis.

Effects of AL 107, a novel semisynthetic cardiac glycoside, on the cardiovascular system in anaesthetized beagle dogs with pentobarbital-induced cardiac insufficiency.

The inotropic efficacy, arrhythmogenicity and cardiohaemodynamic properties of AL 107 (3-alpha-methyl-digitoxigenin glucoside, CAS 62190-59-4), a novel cardiac glycoside, were studied in anaesthetized dogs with pentobarbital-induced acute cardiac insufficiency. Three groups of dogs received AL 107, ouabain or verhicle. The cardiac glycosides were infused intravenously in eight increasing dose levels which where given cumulatively. Slope of left ventricular pressure rise (LVdp/dtmax) increased in the AL 107- and ouabain-treated groups. At the end of the 6th dose level ouabain caused a significantly higher LVdp/dtmax (137 +/- 15% of the baseline value taken before induction of insufficiency) than AL 107 (94 +/- 9%). Further increase of the dose resulted in a reduction of LVdp/dtmax in ouabain-treated dogs, whereas AL 107 continuously increased LVdp/dtmax up to the highest dose infused, where 130 +/- 16% of the baseline value was reached. In ouabain-treated dogs, ECG abnormalities accompanied the decrease of LVdp/dtmax whereas ECG-changes did not interfere with the development of left ventricular contractility in AL 107-treated dogs. The 6th dose of ouabain provoked a maximal increase of cardiac output (CO) (up to 107 +/- 8% of baseline values) and stroke volume (SV) (up to 122 +/- 6% of baseline values) which decreased upon further dose elevation. In the dose-range studied AL-107 induced a continuous increase of both parameters which, however, hardly reached the baseline values. ECG abnormalities occurred in both substance-treated groups and showed quantitative but not qualitative differences. The ECG showed rapid recovery after cessation of AL 107 infusion but did not normalize during a postinfusional recovery period of 1 h after treatment with ouabain. In conclusion, AL 107 increased cardiac performance in an acute canine model of cardiac insufficiency. It was slightly less active than ouabain. However, the ECG disorders were more moderate in AL 107--than in ouabain-treated dogs, a difference which was most pronounced with respect to reversibility in the postinfusional period.

Analgesic effects of 1',1' dimethylheptyl-delta8-THC-11-oic acid (CT3) in mice.

The metabolic pathway leading to carboxylic acid derivatives of cannabinoids was discovered more than twenty years ago. While these compounds showed no cannabimimetic activity, subsequent work documented several biological responses both in vitro and in vivo for the THC acids. These include inhibition of eicosanoid synthesis, antiedema effects, antagonism to PAF actions, inhibition of leucocyte adhesion and anti nociception. In this report we present data further characterizing the analgesic properties of the title substance which is a potent synthetic member of this group. CT3 was effective in the mouse hot plate assay at 48 degrees C showing an ED-50 of 4.31 (3.37-5.83) mg/kg when administered i.v (10% Cremophor EL in saline). When given by gavage in peanut oil, it resulted in 30-40% MPE (maximum possible effect) at 10 mg/kg with the effect persisting for up to 5 hours. A more potent response was observed in the mouse p-phenylquinone writhing test. When given i.v., it showed an ED-50 of 1.24 (0.84-1.75) mg/kg. However, no activity was found with oral administration either in peanut oil or Cremophor EL. At 10 mg/kg i.v., a 100% inhibition of the writhing response was seen. The mouse formalin antinociception test was also studied in animals that received CT3 (4.64 mg/kg) i.v. using three behavioral parameters for activity. The drug showed decreases in each category when compared with vehicle/formalin treated mice. The formalin effect showed a typical two phase, time related, response in which CT3 caused a 64% reduction in the early phase and a 48% reduction in the late phase in a composite score of nociception. Interestingly, it did not alter motor function in the rota rod procedure at 4.64 mg/kg i.v.

Inhibitory effects of thalidomide on cellular proliferation, endoneurial edema and myelin phagocytosis during early wallerian degeneration.

In addition to the well-known teratogenic effect of thalidomide, previous studies have revealed mild immunosuppressive properties and, more recently, an anti-angiogenic activity. To find out more about the specificity of these effects we studied the influence of orally administered thalidomide on Wallerian degeneration in rats. Wallerian degeneration is a potent experimental model for studying reproducible cell proliferation in vivo. Examination of distal nerve segments of transected sciatic nerves from rats that had been treated with thalidomide (2 x 250 mg/kg per day) revealed a significant reduction of endoneurial cell counts at 10-15 days after surgery compared to that seen in controls. This effect was not statistically significant, at a very early stage of Wallerian degeneration, i.e., at 5 days after transection of the nerve. Subperineurial edema and phagocytosis was also reduced, although this was not statistically significant. This apparently nonspecific inhibitory effect of thalidomide during early Wallerian degeneration shown in the present study should be investigated further for its possible relationship to other previously established inhibitory activities of thalidomide, especially its immunosuppressive effect in man.

The beagle dog as a predictor of gastrointestinal findings in humans caused by the prostacyclin analogue taprostene.

Beagle dogs were exposed orally to the prostacyclin analogue taprostene for four weeks. Dose levels of 200-3000 micrograms/kg body weight/day were used. Specific activity of taprostene on the digestive system compared to other species is reported. It is characterized by hypermotility of the gastrointestinal tract resulting in intestinal invagination in some animals. Gastrointestinal symptoms occurred also after intravenous administration indicating a systemic stimulating effect on smooth muscles. Concerning reversible gastrointestinal side effects in humans after intravenous infusion of prostacyclin the results of this subacute toxicity study indicated that the dog is an adequate and sensitive species for preclinical testing of prostacyclins.

Prostaglandin E2, thromboxane B2, and leukotriene B4 release from peritoneal macrophages by different osmotic agents in nonuremic guinea pigs.

Interleukin-1 (Il-1), prostaglandins, and leukotrienes have been identified as inflammatory parameters in the setting of peritoneal dialysis. Recently, it was postulated that chronic overstimulation of peritoneal macrophages (PM) may result in fibrosis and loss of ultrafiltration. The aim of the present study was to investigate whether alternative osmotic agents (polyglucose, amino acids, glycerol, bicarbonate/glucose, gelatine, hydroxyethyl starch) provoke greater eicosanoid release by PMs than glucose. Fifty milliliters of sterile dialysate containing different osmotic agents were injected intraperitoneally into nonuremic guinea pigs. After 4 hours of dwell time, prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and leukotriene B4 (LTB4) production was analyzed in peritoneal effluents using specific radioimmunoassays (RIA) after liquid extraction. Cyclooxygenase products were generated with all osmotic agents: PGE2 concentrations ranged from 0.9 to 2.8 ng/4h, and TXB2 levels ranged from 39 to 49 ng/4h. In addition, the lipoxygenase product LTB4 was found in concentrations between 1.8 and 3.5 ng/4h. There were no significant differences in eicosanoid release among the osmotic agents. Thus, in this experimental setting, the capacity of PM to release inflammatory mediators did not correlate with the chemical composition of the dialysis solutions.