Abstract
The design and development of experimental, in vivo , chronobiological animal models may help reveal some of the relationships between circadian rhythms and biological functions. In vivo experiments require the use of appropriate anaesthesia, which should be selected according to their particular effect on the organism. The aim of study was to review the status of acid-base balance and ion concentration in arterial blood under common used general anaesthesias in experiments in dependence on the light-dark (LD) cycle in spontaneously breathing rats. The experiments were performed using three- to four-month-old pentobarbital (P)-, ketamine/xylazine (K/X)- and zoletil (Z)-aneasthetized female Wistar rats after a four-week adaptation to an LD cycle (12h light:12h dark). It was concluded that P anaesthesia disturbs LD dependence of acid-base balance compared to K/X and Z anaesthesia, but LD differences in plasma ion concentrations are disturbed under all type of general anaesthesia. P anaesthesia is not the most appropriate type of anaesthesia in rat chronobiological experiments. It eliminated LD differences, and also produces a more acidic environment, more pronounced hypercapnia and hypoxia than K/X and Z anaesthesias. This should be taken into account because the altered internal environment may affect the activity of systems whose functions are primarily dependent on acid-base balance or/and ion concentrations.
Highlights
Rats are useful models to study functions of various systems in preclinical trials and toxicological studies [1]
In the light part of the day, the pH values reflect acidosis, compared with the range calculated from other authors in all types of anaesthesia, and there was no significant difference between individual types of anaesthesia
After summarizing the results from the analysis of acid-base balance parameters and ion concentrations from blood plasma, it was concluded that there are differences in the final status of the rat internal environment that depend on the LD cycle and on the type of anaesthesia
Summary
Rats are useful models to study functions of various systems in preclinical trials and toxicological studies [1]. Normative data for pH, arterial blood gases and electrolytes would help identify healthy animals for the experiments. There are few studies that have investigated the reliability of this tool [2]. The time when the experiments were performed and the synchronization of the animals to the light-dark (LD) cycle were not accounted for in the methodologies of these studies. Author (year) Lewis et al [3] Pepelko and Dixon [4] Brun-Pascaud et al [5] Girard et al [6] Hess et al [7] Dettmers [8]
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