Optimization of intraperitoneal injection anesthesia in mice: drugs, dosages, adverse effects, and anesthesia depth

PURPOSE

The goals of the study were to find a safe intraperitoneal injection anesthesia protocol for medium-duration surgery in mice (e.g., embryo transfer/vasectomy) coupled with a simple method to assess anesthesia depth under routine laboratory conditions.

METHODS

Eight anesthetic protocols consisting of combinations of dissociative anesthetics (ketamine, tiletamine), alpha2-agonists (xylazine, medetomidine), and/or sedatives (acepromazine, azaperone, zolazepam) were compared for their safety and efficacy (death rate, surgical tolerance), using observations and reflex tests. The four best protocols were further evaluated during vasectomy: physiologic measurements (respiratory rate, electrocardiogram, arterial blood pressure, body temperature, blood gas tensions, and acid-base balance) were used to characterize the quality of anesthesia. The reactions of physiologic parameters to surgical stimuli were used to determine anesthesia depth, and were correlated with reflex test results.

RESULTS

The protocol with the highest safety margin and the longest time of surgical tolerance (54 min) was ketamine/ xylazine/acepromazine. Three further anesthetic combinations were associated with surgical tolerance: ketamine/ xylazine, ketamine/xylazinelazaperone, and tiletamine/xylazine/zolazepam (Telazol/xylazine). The protocols consisting of ketamine/medetomidine and ketamine/azaperone were not associated with clearly detectable surgical tolerance. The most reliable parameter of surgical tolerance under routine laboratory conditions was the pedal withdrawal reflex.

CONCLUSIONS

The best intraperitoneal injection anesthesia regimen consisted of ketamine/xylazine/acepromazine. The dose must be adapted to the particulars of each experimental design (mouse strain, sex, age, mutation). This is best done by measuring surgical tolerance, using the pedal withdrawal reflex.

A behavioral pharmacological study of mafoprazine, a new phenylpiperazine derivative

Behavioral pharmacological studies on mafoprazine, a new drug for the prevention of aggressive behavior, were performed to compare its effects with those of an existing drug, azaperone (Stresnil). The acute toxicity of mafoprazine in mice was slightly stronger than that of azaperone. Mafoprazine showed the following effects (at 0.2 to 2.0 mg/kg, s.c.): a decrease in spontaneous motor activity, prolongation of the duration of pentobarbital anesthesia, inhibition of long-term isolation-induced aggressive behavior, inhibition of olfactory bulbectomy-induced hyperemotionality and muricide behavior in mice and rats, and a marked taming and tranquilizing effect on aggressive behavior in dogs. These effects of mafoprazine were qualitatively the same as those of azaperone. Mafoprazine showed cataleptogenicity in rats at 5 mg/kg, s.c. or more and motor incoordination in rats at 0.2 mg/kg, s.c. or more. In the experiment on operant behavior in rats, the effect of mafoprazine on differential reinforcement of the low rate (DRL) response was almost the same as those of azaperone and chlorpromazine. These results indicate that mafoprazine has substantially the same psychotropic effect as azaperone, while the former has a weaker action on the extrapyramidal system than the latter, suggesting that mafoprazine could be used as a unique aggression-inhibiting drug.

Mutagenicity evaluation of azaperone in the Salmonella/microsome test

Azaperone was evaluated for its mutagenic potential by the Salmonella/microsome test. No mutagenic activity towards six S. typhimurium strains could be evidenced with azaperone at doses up to 2,000 micrograms/plate, either without or with metabolic activation at usual test conditions. Higher concentrations of liver post-mitochondrial fraction from Aroclor 1254 (ARO)-pretreated rats did not reveal any increase in the number of revertants towards S. typhimurium strains TA1537, TA1538 and TA98. Moreover, a plate-incorporation test with liver post-mitochondrial fractions from mice pretreated with phenobarbital (PB) and a liquid preincubation test with liver post-mitochondrial fractions from rats pretreated with ARO also failed to reveal any mutagenic action of azaperone towards S. typhimurium strain TA98. Thus, none of the tests used provided any indication of azaperone having a mutagenic action.

Combined azaperone and metomidate anaesthesia in liver transplantation in the pig

Combined azaperone and metomidate anaesthesia has been used in 86 surgical procedures on 84 piglets, either as such or deepened and prolonged. 51 animals were sacrificed at the end of the procedure as planned before. The anesthesia allowed the performance of various short and long operations. Out of the 33 remaining pigs, submitted to 35 operations, 4 died during the procedure of a technical fault; 2 did not recover from a deep hypothermia (below 10 degrees C); 1 died from the hepatic coma induced through the operative procedure. The other 26 awoke and recovered spontaneous breathing within 1-4 h following the type of anaesthesia and operating procedure they had submitted, which dured from 15 to 330 min.