Effects of restraint by tether jackets on behavior in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHRs) were compared to Wistar-Kyoto (WKY) and Wistar (WIS) rats on 18 behaviors to determine strain differences while undisturbed and when being restrained by a jacket and tether system often used for monitoring blood pressure chronically. Male SHRs unrestrained in the home cage initially exhibited greater magnitudes of body grooming, quadrant changes, turning, sniffing and rearing than WKYs, whose behavioral levels remained low throughout the entire session. SHRs and WISs gradually declined in behavioral levels within the sessions. The effects of restraint significantly decreased the exploratory/activity behaviors of nose poking, rearing and quadrant changes, with SHRs showing a greater decrement as a result of the restraint. Because of this differential effect of restraint on behaviors distinguishing SHRs and WKYs, studies simultaneously measuring behavior and blood pressure should be interpreted with caution, especially when comparing strains. The hypoactivity of the WKY would suggest the use of an additional control strain in behavioral studies.