Main Indices of Laboratory Rabbit Cardiovascular System

Introduction. Rabbits, ferrets, dogs, miniature pigs and monkeys are considered to be the preferable test systems for assessing the efficacy of the developed medicinal products for the cardiovascular system. The heart rate and distribution of cardiac ion channels in the heart of these species is similar to that in the human heart. The present work focuses on rabbits as they are one of the most widely used species in preclinical research, however, the results of measurements carried out on a sufficient sample of intact animals can hardly be found in the open sources. Thus, the aim of the study is to determine the features of the electrocardiogram and to establish the reference intervals of the key cardiovascular indices as well as of the blood pressure in the sexually mature laboratory rabbits of different breeds, ages and sexes, and to compare the obtained data with that in the literature sources. Materials and Methods . The study was conducted at JSC “Research-and-Manufacturing Company “Home of Pharmacy” (Leningrad Region) in the period from 2019 to 2024. 597 electrocardiograms and 863 values of systolic and diastolic blood pressure in rabbits of various breeds and sexes aged 4 to 8 months were analysed and reference intervals for them were calculated. To minimise possible variability of parameters caused by stress and motor activity of animals, they were anesthetized during physiological studies with a drug containing tiletamine and zolazepam (5 mg / kg) in combination with xylazine hydrochloride (1–2 mg / kg) administered intramuscularly or intravenously. The data were retrieved by recording the background values in all rabbits in the experiment (before administering the studied medicinal products), as well as in rabbits in the control and intact groups. Reference intervals were calculated using a nonparametric (number of values more than 120) or robust (number of values less than 120) methods. Results . When studying the electrocardiograms of rabbits, the highest variability was noted in the P wave. Also, the absence of one of the Q, S, T waves in one or two leads and absence of S-T and T-P intervals were frequently observed. When comparing rabbit breeds and body weight ranges, no significant differences were found in the calculated reference intervals of the indices assessed. When comparing to the literature sources, the electrocardiogram parameters mainly matched the obtained reference intervals, except for the QRS interval. The obtained intervals of blood pressure indices in the state of anaesthesia were significantly lower than the values presented in the literature for the awaken animals. Discussion and Conclusion . The calculated reference intervals of the most of electrocardiogram parameters in different rabbit breeds are comparable to the data available in literature and do not significantly vary in relation to age, weight and sex. The obtained reference intervals and the described features of the electrocardiogram of rabbits can be used in the analysis and interpretation of data received during preclinical research.