Investigating the long-term effect of subchronic phencyclidine-treatment on novel object recognition and the association between the gut microbiota and behavior in the animal model of schizophrenia.

Subchronic phencyclidine (subPCP) treatment induces schizophrenic-like behavior in rodents, including cognitive deficits and increased locomotor sensitivity towards acute administration of PCP. Evidence is accumulating that the gut microbiota (GM) influences behavior through modulation of the microbiota-gut-brain axis, and hence, part of the variation within this animal model may derive from variation in the GM. The aims of this study was to investigate first, the duration of subPCP-induced cognitive impairment in the novel object recognition test, and second, the possible effect of subchronic PCP-treatment on the GM, and the association between the GM and the behavioral parameters. The association was further investigated by antibiotic reduction of the GM. Male Lister Hooded rats were dosed twice daily i.p. with either 5mg/kg PCP or sterile isotonic saline for seven days followed by a seven-day washout period. Rats were tested in the novel object recognition and the locomotor activity assays immediately after, three weeks after, or six weeks after washout, and the fecal GM was analyzed by high throughput sequencing. Antibiotic- and control-treated rats were tested in the same manner following washout. In conclusion, subPCP-treatment impaired novel object recognition up to three weeks after washout, whereas locomotor sensitivity was increased for at least six weeks after washout. Differences in the core gut microbiome immediately after washout suggested subPCP treatment to alter the GM. GM profiles correlated to memory performance. Administration of ampicillin abolished the subPCP-induced memory deficit. It thus seems reasonable to speculate that the GM influences memory performance, contributing to variation within the model.

Fasting of mice: a review.

Fasting of mice is a common procedure performed in association with many different types of experiments mainly in order to reduce variability in investigatory parameters or to facilitate surgical procedures. However, the effects of fasting not directly related to the investigatory parameters are often ignored. The aim of this review is to present and summarize knowledge about the effects of fasting of mice to facilitate optimization of the fasting procedure for any given study and thereby maximize the scientific outcome and minimize the discomfort for the mice and hence ensure high animal welfare. The results are presented from a number of experimental studies, providing evidence for fasting-induced changes in hormone balance, body weight, metabolism, hepatic enzymes, cardiovascular parameters, body temperature and toxicological responses. A description of relevant normal behaviour and standard physiological parameters is given, concluding that mice are primarily nocturnal and consume two-thirds of their total food intake during the night. It is argued that overnight fasting of mice is not comparable with overnight fasting of humans because the mouse has a nocturnal circadian rhythm and a higher metabolic rate. It is suggested that because many physiological parameters are regulated by circadian rhythms, fasting initiated at different points in the circadian rhythm has different impacts and produces different results.

Less invasive blood sampling in the animal laboratory: clinical chemistry and haematology of blood obtained by the Triatominae bug Dipetalogaster maximus.

Dipetalogaster maximus (Dipmax), a blood-sucking bug belonging to the family Reduviidae, has been used to obtain blood samples, for example for clinical chemistry and haematology, in a variety of zoo animals and wildlife. Using this bug allows stress-free blood sampling as the bug is able to draw blood without the mammal noticing the bug. In laboratory animal science, the need for blood samples from unstressed animals may arise, especially in animal behaviour research. The use of Dipmax bugs may prove a valuable tool for this purpose. To validate the method, we compared an array of standard blood parameters sampled from New Zealand White rabbits, sampled either by the use of bugs or by the conventional method; puncture of vena auricularis caudalis. The overall hypothesis was that there was no significant difference in clinical chemistry and haematological parameters between the bug method and the conventional method. A total of 17 clinical parameters as well as 12 haematological parameters were measured and compared in New Zealand White rabbits. The results showed that for 13 of these 29 analysed parameters, the bug method and the conventional method did not give significantly different results, and the obtained results were thus directly comparable. For the remaining parameters the obtained results were significantly different. However, all parameters were measurable in the bug samples. The influences of the bug metabolism on these parameters are discussed.

Pathology, tissue metalloproteinase transcription and haptoglobin responses in mice after experimental challenge with different isolates of Pasteurella multocida obtained from cases of porcine pneumonia.

Pasteurella multocida is a major cause of porcine pneumonia, but the pathogenesis of the disease is poorly defined. The aim of this study was to further understand the host response to infection by use of a mouse model of P. multocida pneumonia. Twenty female mice were divided into four groups (n=5). Three groups were infected with one of three isolates of P. multocida isolated from clinical cases of chronic porcine pneumonia with necrotizing, suppurative and non-suppurative lesions, respectively. The fourth group served as uninfected controls. Mice were killed 24 h postinfection and samples were collected for bacteriology, histopathology and in-situ hybridization for detection of P. multocida. Measurements of expression of genes encoding matrix metalloproteinase 9 (MMP9) and tissue inhibitor of metalloproteinase 1 (TIMP1) in lung tissue and quantification of serum haptoglobin concentration were performed. P. multocida was found in the lung and spleen. Lung lesions were characterized by deposition of fibrin in alveoli and bronchioles, perivascular oedema, suppuration and necrosis. The cellular infiltration was mainly of neutrophils. Splenic neutrophilic infiltration was also evident. Minor differences in the severity and nature of lesions were seen according to the isolate of P. multocida used for infection. Intranasal infection of mice can therefore be used to evaluate the host response and lesions caused by P. multocida obtained from porcine pneumonic infections. The inflammatory response in this model is associated with increased tissue expression of genes encoding MMP9, TIMP1 and serum haptoglobin concentration.

PNMT transgenic mice have an aggressive phenotype.

PNMT (phenylethanolamine-N-methyl-transferase) is the enzyme that catalyzes the formation of epinephrine from norepinephrine. In transgenic mice over-expressing PNMT, observations revealed a very high level of aggression compared to their background strain, C57BL/6J. To evaluate the influence of PNMT on aggression and emotionality in this transgenic line, single-sex male and female groups were independently established that consisted of either four wild-type mice or four transgenic mice overexpressing PNMT. The members of each group were littermates. Mixed single-sex groups consisting of two transgenic mice and two wild-type mice were also established. Almost no fights were observed within the female groups. In males, the transgenic line showed a significantly higher level of fighting than controls (p=0.007) and mixed male groups (p=0.02). Housing mice from the transgenic line in mixed groups with wild-type mice seems to decrease the level of aggression in the transgenic line. In conclusion, this is the first study to demonstrate a clear, significant increase in aggression arising from PNMT overexpression. This suggests an important role for central epinephrine levels in aggressive behavior.