Evaluation on Efficacy and Safety of Tribromoethanol and Tribromoethanol plus α₂-Adrenergic Agonists in Different Mouse Strains

Abstract

The present study was carried out to provide a guideline for injecting tribromoethanol (TBE) as the main anesthetic agent, while adjusting the doses of xylazine (X) and medetomidine (M) according to different strains of mice (male ICR, C57BL/6, and BALB/c). Seven intraperitoneal injection anesthesia protocols using TBE and mixtures of TBE and α 2 -adrenergic agonists (TBE/X and TBE/M) were compared in terms of their efficacy and safety (anesthetic duration, death rate, and the development of pathological lesions of abdominal organs). All animals that were injected with a low dose of TBE (200 mg/kg) displayed clear signs of light anesthesia with a strong pedal withdrawal reflex. Despite the good anesthetic effect, a high dose of TBE (400 mg/kg) was not a suitable anesthetic for major surgery in all mouse strains because of the risk of pathologic changes in the abdominal organs, such as retention of the digestive tract, peritonitis, and fibrinoid adhesion. TBE200/X10 and TBE200/M0.5 (TBE, 200 mg/kg; X, 10 mg/kg; M, 0.5 mg/kg) appeared to be safe and provided satisfactory anesthesia in ICR mice. Finally, there were clear differences in anesthetic efficacy among ICR, C57BL/6, and BALB/c strains. TBE/M and TBE/X did not anesthetize BALB/c mice, and it anesthetized C57BL/6 mice for a short time. When administered with TBE/X and TBE/M maintained the sedation of ICR mice. We were able to establish different regimes for each strain (TBE200/X20 for C57BL/6, TBE300/X10 and TBE200/M1 for BALB/c). Our results showed that TBE/X and TBE/M could be recommended as an anesthetic mixture, with the dose appropriately adjusted according to mouse strain.

Kinetics of proinflammatory cytokines after intraperitoneal injection of tribromoethanol and a tribromoethanol/xylazine combination in ICR mice

“…TBE at 400 mg/kg was a reliable anesthetic that provided surgical anesthesia for approximately 40 min in ICR mice [10]. However, it is recommended that one does not increase the TBE dose since fibrous adhesions in the abdominal cavity, irritation, and mortalities have been reported, especially with high doses or repetitive use [2].…”

“…To understand the underlying pathophysiological changes, we examined the level of cytokines and protein levels through ELISA experiments with abdominal lavage fluid and spleen fluid collected from mice treated with low-dose TBE. TBE at 400 mg/kg was a reliable anesthetic that provided surgical anesthesia for approximately 40 min in ICR mice [ 10 ]. However, it is recommended that one does not increase the TBE dose since fibrous adhesions in the abdominal cavity, irritation, and mortalities have been reported, especially with high doses or repetitive use [ 2 ].…”

“…However, it is recommended that one does not increase the TBE dose since fibrous adhesions in the abdominal cavity, irritation, and mortalities have been reported, especially with high doses or repetitive use [ 2 ]. The combination of 200 mg/kg TBE and 10 mg/kg xylazine induced proper anesthetic depth in ICR mice [ 10 ]. The dose of 400 mg/kg TBE used in protocol 2 was based on doses reported in the literature [ 1 , 8 , 24 ].…”

“…Prolonged stimulation of the inflammatory response may lead to tissue damage and there is evidence linking mice incapable of producing IL-6 with decreased mortality and inflammatory responses when they are injected IP with zymosan [ 33 , 34 ]. It was speculated that there is a correlation between late effects in these cytokine levels and histopathological changes of abdominal organs [ 10 ].…”

“…Despite the good anesthetic effect, severe adverse effects were displayed at 2.5% TBE (400 mg/kg). A mixture of 1.25% TBE (200 mg/kg) and xylazine (10 mg/kg) appeared to be safe and provided satisfactory anesthesia in ICR mice [ 10 ].…”