THE CORRELATION BETWEEN ACTIVITY, BLOOD-PRESSURE AND HEART-RATE IN FREELY MOBILE SPRAGUE-DAWLEY AND TRANSGENIC RATS

Systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR) and locomotor activity have been measured at 1-min intervals for 24 h in Sprague-Dawley (N=5) and for 2x24 h in transgenic hypertensive (N=4) r ats. The animals were freely mobile and entrained to a 12:12 LD cycle (lights on at 0700). The endogenous circadian component of the cardiov ascular variables was removed from the raw data, and then correlations between activity and the residual component (raw data minus the endog enous component) of SEP, DBP and HR were calculated. This calculation was performed twice, in the mid-light and mid-dark phases. We have inv estigated if the mean size of the correlation coefficients depended on cardiovascular variable (SBP, DBP or HR), phase (D or L) or strain (S prague-Dawley, SPD, or Transgenic, TG, rats). Nearly all correlations were positive and ANOVA's showed a significant effect of cardiovascula r variable for both strains, with correlations for HR being significan tly higher than those for SEP and DBP. The mean correlations in the SP D strain were significantly higher than in the TG strain for variables SEP and DBP, but not for HR. The correlations between activity and bl ood pressure were more marked for SPD rats in the light (inactive) tha n dark (active) phase. Both strains showed ultradian rhythms in all va riables, particularly in the light phase. If the analysis was repeated using deviations of the cardiovascular variables from a l-h moving av erage rather than the endogenous circadian component, then the results were very similar. The results are discussed in terms of the links be tween the rhythms of activity and cardiovascular variables, with parti cular reference to differences between the two strains.