RESUMO
The aim of this study was to evaluate and compare the effects of single doses of butorphanol, morphine, and tramadol on gastrointestinal motility in rabbits (Oryctolagus cuniculus) using non-invasive imaging methods, such as radiographic barium follow through and ultrasonographic contraction counts. Time-lapse radiographic and ultrasound examinations were performed before and after a single intramuscular dose of 5 mg kg-1 butorphanol, 10 mg kg-1 morphine, or 10 mg kg-1 tramadol. Pyloric and duodenal contraction counts by ultrasonography and radiographic repletion scores for the stomach and caecum were analysed using a mixed linear model. No significant effect was noted on ultrasound examinations of pyloric and duodenal contractions after administration of an opioid treatment. Morphine had a significant effect on the stomach and the caecum repletion scores, whereas butorphanol had a significant effect only on the caecum repletion score. Tramadol had no significant effect on the stomach or caecum repletion scores. The present findings suggest that a single dose of 5 mg kg-1 butorphanol or 10 mg kg-1 morphine temporarily slows gastrointestinal transit in healthy rabbits, preventing physiological progression of the alimentary bolus without the induction of ileus. In contrast, a single dose of 10 mg kg-1 tramadol has no such effects.
RESUMO
OBJECTIVE: To establish a noninvasive imaging protocol for rabbit gastrointestinal transit evaluation. To assess the effect of a single injection of buprenorphine on the digestive transit of rabbits via this new technique. STUDY DESIGN: Prospective, parallel study. ANIMALS: Fifteen specific pathogen-free male New Zealand White rabbits weighing 2.68 ± 0.28 kg. METHODS: A 10 mL kg-1 barium meal was administered and the rabbits were subjected to serial radiographic and ultrasound examinations without treatment and 1 week later following a single intramuscular dose of 100 µg kg-1 of buprenorphine. Radiographic data from the stomach and caecum were collected and assigned a retention score ranging from 0 (no barium) to 3 (large amount of barium). The resulting scores and pyloric and duodenal contraction counts were analysed using a mixed linear model and are expressed as least square mean (lsm) ± standard error. Transit was estimated based on the apparition time of faeces in the pelvic area and analysed using a Wilcoxon test. A p < 0.05 was considered significant. RESULTS: Buprenorphine treatment induced a higher lsm number of pyloric (1.73 ± 0.19 versus 0.78 ± 0.19, p < 0.01) and lsm duodenal contractions (17.35 ± 1.04 versus 13.44 ± 1.04, p < 0.01). Buprenorphine administration decreased the lsm barium retention score in the stomach (2.44 ± 0.05 versus 2.64 ± 0.05, p < 0.01), but had no effect on the lsm barium retention score in the caecum. The time to apparition of faeces in the pelvic area was not influenced by buprenorphine administration (p = 0.66). CONCLUSIONS AND CLINICAL RELEVANCE: A single high dose of buprenorphine appears to have no adverse effect on gastrointestinal motility in healthy rabbits.