THE EFFECTS OF SYSTOLIC ARTERIAL PRESSURE ON LOCOMOTOR ACTIVITY IN CONGENIC RATS DERIVED FROM STROKE PRONE SPONTANEOUSLY HYPERTENSIVE RATS AND WISTAR KYOTO RATS

Abstract

Objective: The systolic arterial pressure (SAP) levels of congenic rats were reported to be intermediate between those of stroke-prone spontaneously hypertensive (SHRSP) rats and Wistar Kyoto (WKY) rats, and the congenic rats were reported to exhibit higher locomotor activity than SHRSP and WKY rats. Locomotor activity in the early morning was higher in the congenic rats than in the other two strains. However, no study on the relationship between SAP and locomotor activity in congenic rats has been performed. Therefore, we aimed to examine this topic. Design and method: We used 10 mature male congenic rats and age- and gender-matched SHRSP and WKY rats (n = 10 each) as the controls. We measured the SAP and locomotor activity of the rats telemetrically. We estimated best-fit curves of locomotor activity using the maximal entropy method. Results: The congenic rats exhibited the highest locomotor activity counts (congenic rats vs. SHRSP rats vs. WKY rats: 58 (23, 89) vs. 18 (4, 40) vs. 4 (1, 8) counts/10 seconds (median, Q1, Q3), P = 0.0010). The congenic rats also exhibited SAP levels that were intermediate between those of the SHRSP and WKY rats (congenic rats vs. SHRSP rats vs. WKY rats: 194 ± 7 vs. 229 ± 7 vs. 117 ± 4 mmHg (mean ± SD, P = 0.0098). The strongest correlation between locomotor activity and SAP was seen in the congenic rats (Y = -1851.3 + 9.87X, rS = 0.592, P = 0.00001). The ratio of the increase in locomotor activity to the increase in SAP was highest in the congenic rats (congenic rats vs. SHRSP rats vs. WKY rats: 7.05 (4.92, 10.20) vs. 0.04 (0.87, 0.88) vs. 0.11 (3.46, 3.55)(median, Q1, Q3); SHRSP rats vs. congenic rats: P < 0.01; SHRSP rats vs. WKY rats: n.s.; congenic rats vs. WKY rats: P < 0.05). Conclusions: Among these three rat strains, the response of locomotor activity to increases in SAP was strongest in the congenic rats.