Effects of Transdermal Fentanyl Treatment on Acute Pain and Inflammation in Rats with Adjuvant-induced Monoarthritis.

Eliminating unnecessary pain is an important requirement of performing animal experimentation, including reducing and controlling pain of animals used in pain research. The goal of this study was to refine an adjuvant-induced monoarthritis model in rats by providing analgesia with a transdermal fentanyl solution (TFS). Male and female Sprague-Dawley rats, single- or pair-housed, were injected with 20 µL of complete Freund adjuvant (CFA) into the left ankle joint. CFA-injected rats treated with a single dose of transdermal fentanyl solution (0.33 or 1 mg/kg) were compared with an untreated CFA-injected group and sham groups that received either no treatment or TFS treatment (1 mg/kg) during 72 h. At the tested doses, TFS reduced mechanical hyperalgesia and improved the mobility, stance, rearing, and lameness scores at 6 h after CFA injection. Joint circumferences were not reduced by TFS treatment, and no significant differences were detected between the 2 doses of TFS, or between single- and pair-housed rats. Treatment with TFS did not appear to interfere with model development and characteristics. However, overall, the analgesic effect was transient, and several opioid-related side effects were observed.

Effect of Repeated Exposure to Isoflurane on Nest Building and Burrowing in Mice.

Nest building and burrowing are highly motivated natural behaviors in rodents, and changes in these behaviors can serve as welfare assessment tools. In this study, we investigated: 1) the limits of agreement between 2 observers for a refined scoring method for nest-building behavior; 2) the effect of repeated exposure to 15 min of isoflurane on nest-building behavior; 3) the effect of 24 h of grid-floor housing, repeated exposure to 15 min isoflurane, and daily intraperitoneal injection of 0.2 mL 0.9% isotonic saline for 3 d on burrowing behavior; and 4) the effect of exposure to grid-floor housing, isoflurane, and intraperitoneal injections on fecal corticosterone metabolites, body weight, fur status, and sucrose preference in mice. SPF C57BL/6NTac female mice (n = 27) were included in the study and were assessed first for burrowing behavior, followed by 2 wk of rest and then for nesting behavior. The refined scoring method for nest-building activity had good inter observer agreement. According to this method, a single exposure to anesthesia with isoflurane led to a decrease in nest-building activity and sucrose preference; a second exposure to anesthesia with isoflurane had no effect on nest building. Neither grid-floor housing nor repeated exposure to isoflurane anesthesia had any effect on burrowing behavior in mice. In contrast, intraperitoneal injections increased burrowing behavior. In conclusion, a refined scoring method for nest-building activity test that we developed for this study proved to be objective and sensitive to the effect of an initial exposure to anesthesia with isoflurane.

Optimising streptozotocin dosing to minimise renal toxicity and impairment of stomach emptying in male 129/Sv mice.

The streptozotocin (STZ)-induced diabetic mouse model has been extensively used as a model for diabetes and diabetic nephropathy, but it is still influenced by many off-target toxic effects and large variation in diabetes induction. Therefore, the aim of this study was to compare different STZ dosing regimens to optimise animal welfare and minimise unwanted effects of STZ measured by acute renal toxicity, impairment of stomach emptying and weight loss. Male 129/Sv mice were injected with 1 × 50, 1 × 100, 1 × 125, 1 × 150, 1 × 200, 5 × 50, 2 × 100 and 2 × 125 mg/kg STZ or vehicle and euthanized 24 hours after the last injection. All STZ doses were found to induce significant enlargement of the stomach. All multiple doses of STZ increased the albumin:creatinine ratio significantly, and immunohistochemical staining of KIM-1 and Ki-67 was increased by 5 × 50 and 2 × 100 mg/kg STZ. Renal gene expression of Cdkn1a, KIM-1, NGAL and MCP-1 was increased by most of the STZ doses. No difference was found between the double intermediate dose of 2 × 100 mg/kg and the multiple low dose of 5 × 50 mg/kg regarding either stomach enlargement or kidney injury. However, the reduced fasting periods and injections in the 2 × 100 mg/kg STZ group could have lowered the impact on the general condition measured as change in body weight. This shows that the double intermediate dose is a good alternative to the recommended multiple low dose for diabetes induction in these mice. The STZ-induced mouse model has again proven to be a model with large variations affecting both animal welfare and model robustness.

Time-dependent Pathologic and Inflammatory Consequences of Various Blood Sampling Techniques in Mice.

We compared 6 frequently used mouse blood-sampling methods (lateral tail incision; tail-tip amputation; sublingual, submandibular, and saphenous vein puncture; and retrobulbar sinus puncture during isoflurane anesthesia) with regard to induction of local and systemic inflammation, stomach contents, weight changes, and corticosterone levels at 6 h to 12 d after sampling. Local inflammation was assessed through histopathology and assessment of the expression of inflammation and tissue damage-related genes (S1008/9A, Cxcl2, Il1b, Nlrp3, Il6, and Il33) in sampled tissue. Systemic inflammation was assessed through quantification of plasma haptoglobin levels, measurement of blood Il1b expression, and evaluation of histopathologic changes in lung, kidney, liver, and spleen. Apart from slight, transient increases in plasma haptoglobin levels after lateral tail incision, retrobulbar sinus puncture, and saphenous vein puncture, no other signs of systemic inflammation were found. Mice subjected to retrobulbar sinus puncture, sublingual puncture, or isoflurane anesthesia only showed the highest plasma corticosterone concentrations. Retrobulbar sinus puncture had the largest effect on body weight loss. Retrobulbar sinus puncture, sublingual puncture, and submandibular puncture only showed minor and in, most cases, fastresolving inflammation. By contrast, blood sampling by lateral tail incision, tail-tip amputation, or saphenous vein puncture caused tissue damage and inflammation locally at the sampling site, which resolved more slowly compared with head-region sampling techniques, according to results from pathologic and gene expression assessments. Expression of S1008/9A, Cxcl2, Il1b, and Nlrp3 increased 10- to 1000-fold and did not return to baseline until day 6 after sampling or later and did not resolve after tail-tip amputation within the 12-d observation period. Increased expression of genes involved in inflammation and tissue repair correlated with histopathologic changes and may thus represent a quantitative supplement to histopathology. In conclusion, none of the tested methods for obtaining blood samples from mice is superior, according to simultaneous immunologic, histopathologic, and animal welfare-related parameters.

Fasting of male mice - Effects of time point of initiation and duration on clinical chemistry parameters and animal welfare.

Fasting of mice is a common procedure, which can affect the outcome of the study as well as animal welfare. In this study, we assess the effects of fasting, fasting duration and fasting initiation time in relation to light schedule and present suggestions for optimization of fasting. Male C57BL/6NCrl mice were fasted for 0, 3, 6, 12, 18 and 24 hours initiated either in the light period (photophase) or the dark period (scotophase). Body weight, gastric content, body temperature, corticosterone and 19 routine clinical chemistry parameters were evaluated. Fasting caused significant changes in most of the measured parameters. Increasing duration of fasting resulted in increasing physiological changes. Fasting initiated in the scotophase caused more significant changes than fasting initiated in the photophase. To cause the least physiological changes in mice and increase animal welfare, mice should preferably be fasted in the photophase and for the shortest possible period allowed by the experimental purpose of fasting.

Softened food reduces weight loss in the streptozotocin-induced male mouse model of diabetic nephropathy.

The streptozotocin (STZ)-induced diabetic mouse is a widely used model of diabetes and diabetic nephropathy (DN). However, it is a well-known issue that this model is challenged by high weight loss, which despite supportive measures often results in high euthanization rates. To overcome these issues, we hypothesized that supplementing STZ-induced diabetic mice with water-softened chow in addition to normal chow would reduce weight loss, lower the need for supportive treatment, and reduce the number of mice reaching the humane endpoint of 20% weight loss. In a 15 week STZ-induced DN study we demonstrated that diabetic male mice receiving softened chow had reduced acute weight loss following STZ treatment ( p = 0.045) and additionally fewer mice were euthanized due to weight loss. By supplementing the diabetic mice with softened chow, no mice reached 20% weight loss whereas 37.5% of the mice without this supplement reached this humane endpoint ( p = 0.0027). Excretion of corticosterone metabolites in faeces was reduced in diabetic mice on softened chow ( p = 0.0007), suggesting lower levels of general stress. Finally, it was demonstrated that the water-softened chow supplement did not significantly affect the induction of key disease parameters, i.e. %HbA1C and albuminuria nor result in abnormal teeth wear. In conclusion, supplementation of softened food is refining the STZ-induced diabetic mouse model significantly by reducing stress, weight loss and the number of animals sacrificed due to humane endpoints, while maintaining the key phenotypes of diabetes and nephropathy.

A comparison of various methods of blood sampling in mice and rats: Effects on animal welfare.

This study was conducted to investigate the effects of blood sampling on animal welfare in a total of 60 NTac:SD rats and 72 C57BL/6NTac mice of both sexes. Blood was sampled either by sublingual vein puncture, tail vein puncture or by retrobulbar plexus/sinus puncture under light isoflurane anaesthesia and, additionally, by facial vein puncture in mice. Non-punctured animals as well as isoflurane-anaesthetised animals were used as controls. Pre- and post-puncture sucrose intake (1.5% w/w) was measured in rats, and nest building scores were studied in mice for 24 h post-puncture. Post-puncture activity and anxiety levels of rats and mice were measured using an elevated plus maze test and an open field test. Stress levels 24 h post-puncture were assessed by analysing faecal corticosteroid metabolites. Sucrose intake and faecal corticosteroid levels were not affected by the blood sampling procedures. Rats showed reduced activity in the open field test and an increased level of anxiety in the elevated plus maze test following retrobulbar plexus puncture and isoflurane anaesthesia. In mice, nest building activity was affected in all the groups compared with the control group, except for animals subjected to facial vein puncture. Retrobulbar sinus puncture, tail vein puncture and sublingual puncture in mice resulted in reduced activity and increased anxiety. We conclude that, of the tested methods, puncture of the tail vein and the sublingual vein have the least adverse effects in rats, whereas facial vein puncture had the least adverse effects on the welfare parameters in mice.

Cilostazol induces C-fos expression in the trigeminal nucleus caudalis and behavioural changes suggestive of headache with the migraine-like feature photophobia in female rats.

Introduction Research in development of new migraine therapeutics is hindered by the lack of suitable, predictive animal models. Cilostazol provokes headache in healthy humans and migraineurs by increasing intracellular cAMP levels. We aimed to investigate whether cilostazol could provoke headache-like behaviours and c-fos expression in rats. In order to evaluate the predictive validity of the model, we examined the response to the migraine specific drug sumatriptan. Methods The effect of cilostazol (125 mg/kg p.o.) in female Sprague Dawley rats was evaluated on a range of spontaneous behavioural parameters, light sensitivity and mechanical sensitivity thresholds. We also measured c-fos expression in the trigeminal nucleus caudalis. Results Cilostazol increased light sensitivity and grooming behaviour. These manifestations were not inhibited by sumatriptan. Cilostazol also induced c-fos expression in the trigeminal nucleus caudalis. Furthermore, trigeminal - but not hind paw hyperalgesia was observed. Conclusion The altered behaviours are suggestive of cilostazol induced headache with migraine-like features, but not specific. The presence of head specific hyperalgesia and the c-fos response in the trigeminal nucleus caudalis imply that the model involves trigeminal nociception. The model will be useful for studying mechanisms related to the cAMP pathway in headache, but its predictive properties appear to be more limited due to the lack of response to sumatriptan.

Infusion of low dose glyceryl trinitrate has no consistent effect on burrowing behavior, running wheel activity and light sensitivity in female rats.

INTRODUCTION: Glyceryl trinitrate induces headache during infusion to man and migraine patients develop an additional migraine attack a few hours after the infusion. Recently, we have moved this model into rat with the intention of developing an animal model predictive of migraine therapy. In the current paper we have studied the effect of glyceryl trinitrate infusion on three different rat behaviors. METHODS: The stability of burrowing behavior, running wheel activity and light sensitivity towards repeated testing was evaluated also with respect to estrous cycle. Finally, the effect of glyceryl trinitrate on these behaviors in female rats was observed. RESULTS: Burrowing behavior and running wheel activity were stable in the individual rat between experiments. The burrowing behavior was significantly affected by the stage of estrous cycle. The other assays were stable throughout the cycle. None of the three behavioral tests were altered by glyceryl trinitrate infusion. In the light-dark box, some batches of rats showed light sensitivity after treatment with glyceryl trinitrate but it could not be repeated in other batches of rats. DISCUSSION: We have investigated the stability towards repeated testing and the effect of i.v. glyceryl trinitrate infusion to awake rats in three behavioral assays. Of the assays evaluated, only light sensitivity was capable of detecting changes after glyceryl trinitrate infusion but, this was not repeatable. Thus, the infusion of a low dose glyceryl trinitrate to concious rats together with the chosen behavioral tests is not a robust setup for studying immediate GTN induced headache behavior in rats.

The origin of Pasteurella multocida impacts pathology and inflammation when assessed in a mouse model.

Host-pathogen interactions of Pasteurella multocida isolates of different origin were studied in a mouse model, focusing on pathology, bacterial load and expression of the metalloproteinase MMP9 and its inhibitor TIMP1. Intranasal inoculation with one of three doses (10(6), 10(4), 10(2)CFU) of an isolate from porcine pneumonia or fowl cholera showed marked differences between the two isolates. The avian isolate was highly pathogenic with severe signs of necrotizing pneumonia, liver necrosis and high bacterial load in lung and liver. Clinical signs and pathology related to the porcine isolate were dose dependent and consisted of exudative bronchopneumonia, abscess formation in liver and a lower bacterial load in lung and liver. Both isolates caused increased expression of MMP9 and TIMP1. In conclusion, evaluation and comparison of pathogenicity and host-pathogen interaction of P. multocida isolates from different hosts is possible in the intranasal murine model.

Dietary magnesium deficiency affects gut microbiota and anxiety-like behaviour in C57BL/6N mice.

OBJECTIVE: Magnesium deficiency has been associated with anxiety in humans, and rodent studies have demonstrated the gut microbiota to impact behaviour. METHODS: We investigated the impact of 6 weeks of dietary magnesium deficiency on gut microbiota composition and anxiety-like behaviour and whether there was a link between the two. A total of 20 C57BL/6 mice, fed either a standard diet or a magnesium-deficient diet for 6 weeks, were tested using the light-dark box anxiety test. Gut microbiota composition was analysed by denaturation gradient gel electrophoresis. RESULTS: We demonstrated that the gut microbiota composition correlated significantly with the behaviour of dietary unchallenged mice. A magnesium-deficient diet altered the gut microbiota, and was associated with altered anxiety-like behaviour, measured by decreased latency to enter the light box. CONCLUSION: Magnesium deficiency altered behavior. The duration of magnesium deficiency is suggested to influence behaviour in the evaluated test.

Manual versus automated blood sampling: impact of repeated blood sampling on stress parameters and behavior in male NMRI mice.

Facial vein (cheek blood) and caudal vein (tail blood) phlebotomy are two commonly used techniques for obtaining blood samples from laboratory mice, while automated blood sampling through a permanent catheter is a relatively new technique in mice. The present study compared physiological parameters, glucocorticoid dynamics as well as the behavior of mice sampled repeatedly for 24 h by cheek blood, tail blood or automated blood sampling from the carotid artery. Mice subjected to cheek blood sampling lost significantly more body weight, had elevated levels of plasma corticosterone, excreted more fecal corticosterone metabolites, and expressed more anxious behavior than did the mice of the other groups. Plasma corticosterone levels of mice subjected to tail blood sampling were also elevated, although less significantly. Mice subjected to automated blood sampling were less affected with regard to the parameters measured, and expressed less anxious behavior. We conclude that repeated blood sampling by automated blood sampling and from the tail vein is less stressful than cheek blood sampling. The choice between automated blood sampling and tail blood sampling should be based on the study requirements, the resources of the laboratory and skills of the staff.

Spatial discrimination and visual discrimination: two methods evaluating learning and memory in juvenile Göttingen minipigs.

Two methods investigating learning and memory in juvenile Göttingen minipigs were evaluated for potential use in preclinical toxicity testing. Twelve minipigs were tested using a spatial hole-board discrimination test including a learning phase and two memory phases. Five minipigs were tested in a visual discrimination test. The juvenile minipigs were able to learn the spatial hole-board discrimination test and showed improved working and reference memory during the learning phase. Performance in the memory phases was affected by the retention intervals, but the minipigs were able to remember the concept of the test in both memory phases. Working memory and reference memory were significantly improved in the last trials of the memory phases. In the visual discrimination test, the minipigs learned to discriminate between the three figures presented to them within 9-14 sessions. For the memory test, all minipigs performed 9/12 correct choices or better. Juvenile Göttingen minipigs are able to learn to perform in a spatial hole-board discrimination test as well as in a visual discrimination test, showing an increase in performance over time. Both tests have considerable scope to assess learning and memory of pigs, and we seem to have succeeded in establishing two test systems suitable for performing preclinical toxicity testing in juvenile minipigs.

Behaviour of postnatally growth-impaired mice during malnutrition and after partial weight recovery.

OBJECTIVES: Early malnutrition is a highly prevalent condition in developing countries. Different rodent models of postnatal early malnutrition have been used to approach the subject experimentally, inducing early malnutrition by maternal malnutrition, temporal maternal separation, manipulation of litter size or the surgical nipple ligation to impair lactation. Studies on the behaviour of (previously) malnourished animals using animal models have produced sometimes contradictory results regarding the effects of early postnatal malnutrition and have been criticized for introducing potential confounding factors. The present paper is a first report on the behavioural effects of early malnutrition induced by an alternative approach: mice nursed by α-casein-deficient knockout dams showed a severe growth delay during early development and substantial catch-up growth after weaning when compared with animals nursed by wild-type females. METHODS: Established behavioural tests were used to study the consequences of early postnatal malnutrition on mouse pups at weaning and after partial weight recovery. RESULTS: Despite the impaired growth, the only behavioural difference between malnourished and normally growing animals was found in exploratory behaviour during acute malnutrition at the time of weaning. After partial catch-up in weight early protein malnourished animals showed no indication of lasting effects on general activity, emotionality and exploration, memory, and pain reactivity. DISCUSSION: These results suggest that the role of early nutrition on behavioural development after recovery in animal models may have been overestimated. Further careful examination of this animal model in terms of maternal care and offspring behaviour will be necessary to confirm if mice nursed by α-casein-deficient dams offer an alternative to existing models while eliminating potential confounding factors.

Welfare assessment in transgenic pigs expressing green fluorescent protein (GFP).

Since large animal transgenesis has been successfully attempted for the first time about 25 years ago, the technology has been applied in various lines of transgenic pigs. Nevertheless one of the concerns with the technology--animal welfare--has not been approached through systematic assessment and statements regarding the welfare of transgenic pigs have been based on anecdotal observations during early stages of transgenic programs. The main aim of the present study was therefore to perform an extensive welfare assessment comparing heterozygous transgenic animals expressing GFP with wildtype animals along various stages of post natal development. The protocol used covered reproductory performance and behaviour in GFP and wildtype sows and general health and development, social behaviour, exploratory behaviour and emotionality in GFP and wildtype littermates from birth until an age of roughly 4 months. The absence of significant differences between GFP and wildtype animals in the parameters observed suggests that the transgenic animals in question are unlikely to suffer from deleterious effects of transgene expression on their welfare and thus support existing anecdotal observations of pigs expressing GFP as healthy. Although the results are not surprising in the light of previous experience, they give a more solid fundament to the evaluation of GFP expression as being relatively non-invasive in pigs. The present study may furthermore serve as starting point for researchers aiming at a systematic characterization of welfare relevant effects in the line of transgenic pigs they are working with.

Milk lacking α-casein leads to permanent reduction in body size in mice.

The major physiological function of milk is the transport of amino acids, carbohydrates, lipids and minerals to mammalian offspring. Caseins, the major milk proteins, are secreted in the form of a micelle consisting of protein and calcium-phosphate.We have analysed the role of the milk protein α-casein by inactivating the corresponding gene in mice. Absence of α-casein protein significantly curtails secretion of other milk proteins and calcium-phosphate, suggesting a role for α-casein in the establishment of casein micelles. In contrast, secretion of albumin, which is not synthesized in the mammary epithelium, into milk is not reduced. The absence of α-casein also significantly inhibits transcription of the other casein genes. α-Casein deficiency severely delays pup growth during lactation and results in a life-long body size reduction compared to control animals, but has only transient effects on physical and behavioural development of the pups. The data support a critical role for α-casein in casein micelle assembly. The results also confirm lactation as a critical window of metabolic programming and suggest milk protein concentration as a decisive factor in determining adult body weight.