24-Hour Profile of Blood Pressure, Heart Rate, Excretion of Electrolytes, and Locomotor Activity in Wistar-Kyoto and SHR Rats Under Conditions of Free-Run Rhythm

Abstract

We presented the results of our study of chronostructure of BP, HR, electrolyte excretion, and locomotor activity under conditions of “free-run rhythm” (light deprivation). In adult male Wistar-Kyoto (normotensive) and SHR (spontaneously hypertensive) rats, BP, biopotentials of the heart (ECG), and locomotor activity were recorded over 24 h by telemetric monitoring and the rate of excretion of electrolytes (Na⁺, K⁺, Ca²⁺, and Mg²⁺) during the nighttime and daytime hours was measured. It was found that under free-run rhythm, 24-h profiles of BP, HR, excretory function of the kidneys, and locomotor activity underwent more considerable changes in normotensive Wistar-Kyoto rats in comparison with hypertensive SHR rats. However, hypertensive rats demonstrated pronounced changes in rhythmic characteristics of HR, which can restrict adaptation reserves of the cardiovascular system.