Effects of Medetomidine on Analgesia and Sedation in Rats

다국어 초록 (Multilingual Abstract)

The effects of medetomidine on the degree of analgesia and sedation in rats were evaluated. The rats were randomly divided into six groups: saline, 1 mL/kg (group ‘Saline’); butorphanol, 2.0 mg/kg; medetomidine, 0.2, 0.4,0.8 or 1.6 mg/kg (group ‘MED0.2’, ‘MED0.4’, ‘MED0.8’ and ‘MED1.6’, respectively). The degree of analgesia was measured in the 50°C hot-water tail-flick latency test, and the degree of sedation was evaluated using the numerical sedation score (NSS) and the righting reflex. All doses of medetomidine, except MED0.2, significantly increased the analgesic effect compared to the Saline group. Variables in the MED0.4 and MED0.8 groups, but not in the MED1.6group, were significantly increased compared to those in the MED0.2 group. However, analgesia with all doses of medetomidine was not significantly different compared to that with butorphanol. Saline and butorphanol treatments did not induce sedation and loss of righting reflex during the recording period. NSS in the MED0.4, MED0.8 and MED1.6 groups were significantly higher than that in the MED0.2 group. NSS in the MED0.8 and MED1.6 groups were not significantly different from that in the MED0.4 group. The latency to loss of righting reflex in the MED0.8and MED1.6 groups decreased significantly compared to that in the MED0.2 group. Thus, 0.4 and 0.8 mg/kg of medetomidine provided not only reliable analgesia but also sedation to rats. In conclusion, 0.4 to 0.8 mg/kg medetomidine could be a useful chemical restraint method in rats.

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