Transcranial direct current stimulation (tDCS) for painless, non-invasive brain stimulation is a promising approach to enhance recovery after stroke. However, the precise molecular and cellular mechanisms underlying the effects of tDCS remain unclear, impeding its use in humans and necessitating research in experimental animals. Unlike humans, who receive tDCS fully awake, experimental models of tDCS have so far been conducted under anaesthesia to ensure the immobility required by currently available experimental setups. The use of anaesthesia may, however, confound results, decreasing their translational value. To address this problem, we developed a refined method enabling tDCS in awake and freely moving mice. A tube attached to the skull contains the stimulation electrode, whose position can be adapted flexibly to the target brain region; the reference electrode is implanted subcutaneously at the contralateral chest. Here, we report n = 135 awake mice that underwent tDCS in their home cage for up to 15 minutes per session over 10 consecutive days. None of those animals showed any adverse effects, neither regarding their general wellbeing, body weight, and behavioural activity, nor in ex vivo histology and immunohistochemistry. We suggest using this refined approach in future experimental studies of neuropsychological disorders.

No systematic procedures exist to ensure that differences in animal sensory capacities are accounted for in experimental design and ethical review processes. This oversight can compromise both scientific validity and animal welfare. This review presents three practical methodologies to address this gap: incorporation of specialist expertise through consultation frameworks, voluntary certification schemes modeled on Open Science practices, and mandatory sensory capacity review integrated into existing ethics committee processes. We provide a concrete tool-a sensory modality survey-that can be implemented by institutional review committees to evaluate sensory considerations in research proposals systematically. These approaches align with the 3Rs principles by enhancing experimental refinement and potentially reducing animal use through improved study design.

The use of Vascular Access Buttons™ (VABs) is gaining traction in animal research as a less invasive alternative to traditional venipuncture methods and a superior option compared with existing alternatives, such as vascular access ports (VAPs). By enabling repeated blood collection and intravenous drug administration with reduced stress and discomfort for the animals, VABs contribute to improved data quality and enhanced animal welfare in animal studies. While increasingly used in rodents, their application in non-rodent species remains underexplored. This study evaluated the feasibility and reliability of the VAB system in two Göttingen Minipigs, comparing its performance with the conventional vena cava cranialis puncture. Pharmacokinetic assessments and clinical pathology analyses revealed consistent results across both techniques, demonstrating the VAB system's ability to generate reproducible, high-quality data. Additionally, its durability and ease of use highlight its potential as a practical and ethical alternative to both traditional venipunctures and VAPs in pharmacokinetic and long-term studies in minipigs. These findings support the integration of the VAB system in toxicological and pharmacokinetic research, particularly in studies requiring repeated blood collection or chronic intravenous dosing.

Isolated kidney perfusion forms the bridge between in vitro and in vivo experiments and is mainly performed with rodent kidneys. It enables the controlled investigation of kidney function without systemic influences and is therefore currently, for instance, considered the gold standard for investigating the regulation of renin release, a central regulator of blood pressure. Renin secretion is controlled by several intrarenal signalling cascades and thus cannot be fully modelled in cell cultures. On the other hand, the in vivo investigation of renin release is confounded by systemic counter-regulatory systemic mechanisms. For ethical and logistical reasons, human kidney tissue has not been used for isolated organ perfusion yet. To reduce the use of rodents and to achieve the translation to larger species, including humans, we developed a method for isolated perfusion of slaughterhouse pig kidney segments. This method allows for future use with human kidney segments obtained from nephrectomies. Pig kidney segments were perfused at constant pressure and renin secretion was determined. The sympathomimetic agent isoproterenol, the Ca2+ chelator ethylene glycol tetraacetic acid, the NO-donor S-nitroso-N-acetylpenicillamine and the loop diuretic bumetanide stimulated renin release while angiotensin II suppressed it. These responses were similar to those observed in isolated perfused rodent kidneys, demonstrating that central regulatory mechanisms of renin release are conserved across species and in tissue segments. Moreover, the newly developed model of perfusion of kidney segments of large animals is suitable for the investigation of renin release from human kidneys and provides an ethical method for isolated kidney perfusion in accordance with animal welfare.

The streptozotocin (STZ)-induced hyperglycaemic rat model is widely used in diabetes research, particularly for investigating diabetic retinopathy; however, animal welfare concerns are often underreported. This study evaluated welfare outcomes in two commonly used rat lines, Brown Norway (BN/Crl) and Sprague Dawley (RjHan:SD). Data were collected from a series of diabetic retinopathy studies, in which a total of 183 BN/Crl and 76 RjHan:SD male rats received 40-65 mg/kg STZ via intraperitoneal injection and were monitored for 5-12 weeks. Welfare parameters, including body weight development and urologic complications (notably paraphimosis), were recorded and compared. Both lines achieved hyperglycaemia (≥16 mmol/l) within three weeks. However, BN/Crl rats exhibited a high incidence (82.5%) and severity of paraphimosis, along with marked weight loss, resulting in 13.7% of the animals reaching humane endpoint criteria for euthanasia. Weight loss positively correlated with STZ doses, with the highest dose (65 mg/kg) leading to 17.2% humane endpoint rate. In contrast, RjHan:SD rats exhibited significantly fewer urologic complications and maintained better weight gain, with none reaching humane endpoint. Our findings suggest that, while BN/Crl rats may offer advantages for ocular research owing to their pigmented eyes, their susceptibility to severe welfare issues raises concerns regarding their routine use. Furthermore, standardised supportive treatments, such as insulin supplementation, are worth considering for the model. This study highlights that careful selection of model animals, disease induction protocols and supportive treatments can optimise research outcomes and avoid loss of experimental animals, while adhering to the 3Rs.

To provide an alternative to oral gavage for per os treatments in laboratory mice, we have recently developed and introduced the micropipette-guided drug administration (MDA) method. This procedure is based on the presentation of a palatable solution consisting of sweetened condensed milk diluted with water, encouraging voluntary consumption of the vehicle and drug formulations. In this study, we compared the MDA method in male and female C57BL/6N and BALB/c mice, two inbred strains widely used in basic and preclinical research. Administering a diluted condensed milk solution daily over a period of 30 days, we observed that male C57BL/6N mice reached the fully voluntary drinking stage within five days or less, requiring the least amount of time to drink from the micropipette. Compared with males, female C57BL/6N mice showed increased consumption times during the initial administration period, yet they all managed to reach a fully voluntary stage within seven days or less. By contrast, BALB/c mice in general, and female BALB/c mice in particular, consistently required more time to consume the diluted condensed milk solution, whether administered voluntarily (no restraint) or semi-voluntarily (with mild tail restraint). Notably, a substantial portion of BALB/c mice (12.5% of males and 62.5% of females) failed to achieve fully voluntary consumption by MDA, despite their ability and willingness to drink the condensed milk solution when using a mild tail restraint. Taken together, the present study identified significant strain and sex differences in the MDA method as applied to laboratory mice.

The light regulation within laboratory environments is critical for ensuring the wellbeing and accurate study of nocturnal animals like Syrian hamsters. This study evaluated the instinctual light color preferences of 18 adult female Syrian hamsters under controlled conditions. The experiment exposed hamsters to four different light colors - blue, red, green, and yellow - under identical irradiance during both day and night phases. The time spent in each light zone was recorded and analyzed using chi-square and mixed model type III analysis. Results showed a significant preference for blue light during the day and red light at night. These preferences align with the physiological needs of hamsters, confirming that previously established light conditions in laboratory settings inadvertently matched their natural inclinations. This study contributes to optimizing light protocols in animal research to improve both welfare and experimental accuracy.