Characterization of the relationship between spontaneous locomotor activity and cardiovascular parameters in conscious freely moving rats

Abstract

In freely behaving rats, variations in heart rate (HR) and blood pressure (BP) are coupled closely with changes in locomotor activity (Act). We have attempted to characterize this relationship mathematically. In 10- and 16-week-old rats, HR, BP and Act were recorded telemetrically every minute for 2 days under 12h:12h light-dark cycling. After examining data for individual rats, we found that the relationship between Act and HR could be approximated by the negative exponential function HR(Act)=HRmax−(HRmax−HRmin)*exp(−Act/Acte), where HRmax, HRmin and, Acte are constants. These constants were calculated separately for light and dark periods by non-linear curve fitting. HR corresponding to maximal locomotion was similar during the light and dark phases, while HR at rest during the dark phase was higher than during the light phase. The range of HR variability associated with Act during the dark phase was similar in young and older animals, but minimal HR was significantly lower in older rats. The relationship between Act and BP was approximated with a similar function. We have found no differences between BP at rest and at maximal locomotion between light and dark and between 10-week and 16-week-old rats. Our results indicate that in rats, cardiovascular parameters are coupled to locomotion to a high degree; however both the HR and the BP reach maximal values when locomotor activity is relatively low. We also found that the phase of daily cycle affects HR in conscious rats independent of locomotor activity.

Neuropharmacological and antibacterial effects of the ethyl acetate extract of Diospyros malabarica (Ebenaceae) seeds

“…The anxiolytic-like effect of D. malabarica extract was also assessed using LDT box. We found that the mice treated with this extract spent more time in lightened side rather than darker one, which clearly indicates the possibility of having anxiolytic efficacy (transition parameter being highly dependent on locomotor activity) of the plants extract [23]. The effect may be due to agonistic effect of extract on GABA/BZD receptor complex, or antagonize 5-HT1B receptor, or agonize 5-HT1A receptor [20,24].…”

Weak General but No Specific Habituation in Anticipating Stimuli of Presumed Negative and Positive Valence by Weaned Piglets

“…Nevertheless, the variety of stimuli used here may have led to additional variability in the data, indicating that aspects other than valence were more prominent to the piglets. Only few stimuli have indeed been tested in respect to their valence and it seems that this task is more difficult than one could naïvely assume ([ 45 ], this volume). More effort should therefore be put in establishing the valence of stimuli in an independent way before using them in experiments.…”

“…We used activity, heart rate, heart rate corrected for activity (expressed also as a ratio [ 45 ]), and heart rate variability (RMSSD and sdnn/RMSSD) as outcome variables in the preliminary evaluation. The ratio of heart-rate corrected for activity was used to account for the fact that increased activity alone can change heart-rate parameters [ 45 ]. Using a log transformation for all the outcome variables resulted in errors and random effects that were normally distributed.…”

“…In the final evaluation, we expressed the piglet’s reactions on days 2–5 relative to their baseline on day 1 in each week (we used a ratio to do so). We did so for the general movement activity, heart rate, heart rate corrected for activity (expressed also as a ratio [ 45 ]), RMSSD, and sdnn/RMSSD.…”