PATTERNS OF BEHAVIORAL-DEVELOPMENT IN SPONTANEOUSLY HYPERTENSIVE RATS AND WISTAR-KYOTO NORMOTENSIVE CONTROLS

The behavior of spontaneously hypertensive (SHR) rats and stroke-prone hypertensive (SP-SHR) male rats during the development and maintenance of elevated blood pressure was examined and compared with age- and gender-matched normotensive (WKY) rats of the same Wistar-Kyoto strain as controls. Rats of each strain (n = 10/age group) were isolated in individual cages and observed for 60 min at 3, 4, 6, 8, 10 or 20 wk of age using a scan sampling technique. At all ages SHR rats were significantly more active than WKY rats whereas SP-SHR rats were intermediate in level of activity. In a 2nd series, activity of male rats of each strain was monitored continuously for 24 h in the home cage. No strain differences in amount or pattern or total daily activity were evident at either 4-6 or 16-18 wk of age. SHR rats are probably more reactive to environmental change but the intermediate level of activity of SP-SHR rats suggests that this response is not related to the degree of blood pressure elevation.