General anaesthesia appears to disrupt cardiovascular stability by causing changes in cardiac function. The assessement of the chronobiological aspects of the pentobarbital anaesthesia impact on myocardial electrophysiology, acid-base balance and ion concentrations in a rat model was the aim of present study. The study was performed using pentobarbital-anaesthetized (40 mg/kg, intraperitoneal) female Wistar rats after adaptation to a 12h light : 12h dark (LD) cycle. Heart rate, rectal temperature, PQ interval, QT interval, QRS complex, QTc interval, and P, R and T wave amplitudes, acid-base balance and arterial concentrations of Na+, K+, Ca2+ and Cl– were evaluated for their dependence on the LD cycle. LD differences were found in heart rate and rectal temperature measured before administration of the anaesthetic agent. Pentobarbital anaesthesia, however, eliminated LD differences in all electrophysiological parameters, parameters of acid-base balance and ion concentrations. LD differences with borderline statistical significance were found only for Na+ levels, with a higher level in the light (ie, nonactive) period. Results of the present study suggest that pentobarbital is probably not the most suitable anaesthetic agent for chronobiological myocardial electrophysiological studies in rat models.
Key words: chronobiology, myocardial electrophysiology, acid-base balance, ion concentration; pentobarbital