Effects of acute chemotherapy-induced mucositis on spontaneous behaviour and the grimace scale in laboratory rats.

Intestinal mucositis is a frequent side-effect of chemotherapy treatment. Many oncological research programs aim to identify novel treatments for this distressing condition, and these programs frequently use rat models. Little is known about the presence and progression of pain in these models and how this can best be treated by analgesic therapy. We used a number of behaviour-based methods of pain assessment to determine which tools were best suited for pain identification. Baseline measures for behavioural assessment, rat grimace score and sociability were determined through analysis of continuously recorded video data and an applied social interaction test (n = 16). Mucositis was then induced by intraperitoneal injection of 5-fluorouracil (150 mg/kg) and further behavioural analyses undertaken. An assessment of enrichment interaction was also made by determining the mass of a plastic chew toy gnawed both pre- and post-chemotherapy injection. Behavioural scoring was performed 1, 6, 12, 24 and 48 h after injection, with facial expression being scored at the 12, 24 and 48 h time-points. Sociability testing was performed once during the post-injection period. No significant differences were found in grimace scores between baseline and later daily measures. Behaviours similar to those previously reported post-laparotomy were observed. Writhing, twitching and back-arching behaviours were most evident in rats affected by mucositis and were increased in frequency (respective P values: 0.002, 0.004 and 0.008) 48 h after chemotherapy injection compared with baseline, implying that pain onset occurred around this time-point. Social investigatory behaviour was also increased (P = 0.002) following disease onset. Each day, rats post-5FU injection gnawed a greater percentage of their Nylabone enrichment by weight than the saline-injected control rats (P = 0.046). These data suggest that, of the tools tested, behavioural assessment scoring may find greatest utility in rodent models of intestinal mucositis and should be investigated further.

The assessment of general well-being using spontaneous burrowing behaviour in a short-term model of chemotherapy-induced mucositis in the rat.

Mucositis is a common and serious side-effect experienced by cancer patients during treatment with chemotherapeutic agents. Consequently, programmes of research focus on the elucidation of novel therapeutics for alleviation of mucositis symptoms, and these frequently use animal models. However, although these models are assumed to be painful and distressing to the animal, endpoints are difficult to determine. The aim of this study was to evaluate whether a change in burrowing behaviour could provide an indication of disease onset and potentially be applied as a humane endpoint. Baseline burrowing behaviour was measured in healthy animals on three occasions by determining the weight of gravel displaced from a hollow tube. Mucositis was then induced in the same animals by intraperitoneal injection of 5-fluorouracil (150 mg/kg) and burrowing behaviour recorded over three consecutive days. Standard measures of disease progression, including body weight loss and clinical score, were also made. The presence of mucositis was confirmed at necropsy by findings of decreased duodenal and colon lengths, and reduced liver, spleen and thymus weights in comparison with non-treated control animals. Histological score of the jejunum and ileum was also significantly increased. Mucositis onset coincided with a decrease in mean burrowing behaviour which was progressive, however this result did not achieve statistical significance (P = 0.66).We conclude that burrowing may be a useful indicator of inflammation in the mucositis model, although this requires further characterization. Pre-selection of animals into treatment groups based on their prior burrowing performance should be pursued in further studies.

Optimization of the non-invasive 13C-sucrose breath test in a rat model of methotrexate-induced mucositis.

PURPOSE: In order to determine the sensitivity and specificity of the test and to optimize experimental conditions utilizing the SBT in a rat model of chemotherapy-induced small intestinal damage. METHODS: Initially, a 13C-sucrose dose-response study was performed in rats to determine an optimal sucrose concentration for the SBT; then applied to assess chemotherapy-induced intestinal damage. A further study was conducted to establish a SBT time-course of methotrexate-induced small intestinal damage and repair. Animals were killed at 96 or 144 h. RESULTS: A sucrose concentration of 0.25 g/ml was optimal (20% CV) for reproducibility and detection of intestinal damage. Maximal damage occurred at 72 h, small intestinal repair was initiated by 96 h and continued at 144 h post-MTX, as determined by the SBT and confirmed by biochemical analyses. Levels of sensitivity and specificity for the SBT were 98 and 94%, respectively. CONCLUSIONS: The SBT is a reliable non-invasive marker of small intestinal health and damage with a high degree of sensitivity and specificity.

The effects of formula feeding on physiological and immunological parameters in the gut of neonatal rats.

A unique model of formula feeding in the neonatal rat was utilized to investigate the effects of an enterally delivered artificial milk formula on clinically relevant immunological and biological characteristics in the gut, compared to naturally reared pups. Hooded Wistar rat pups were randomly allocated to two treatment groups: formula-fed (FF) or naturally suckled (NS). A flexible silastic intra-gastric cannula was surgically implanted into the FF pups, through which an artificial rat milk supplement was continuously delivered from day 4 to day 10 of life. Rat pups were sacrificed at 10 days of age. Body weight, small intestinal weight, mucosal CD8(+) cell numbers, and ileal lactase activity in FF animals were significantly decreased compared to their NS counterparts (P < 0.05). Numbers of eosinophils, mucosal mast cells, CD4(+) T-cells, ileal villus height and gastric emptying times were significantly increased in FF pups (P < 0.05). We have developed a new rat model of artificial feeding which possesses important immunological and biological similarities to the premature human infant.