Effects of cage enrichment on heart rate, blood pressure, and activity of female Sprague-Dawley and spontaneously hypertensive rats at rest and after acute challenges.

Here we sought to determine whether a nonsocial cage enrichment program, identical to one we previously used with male rats, was effective in reducing heart rate or systolic blood pressure (SBP) in female Sprague-Dawley rats and spontaneously hypertensive rats (SHR). Young adult rats, each instrumented with a radiotelemetry pressure transmitter, were housed individually under enriched or nonenriched conditions. Heart rate and SBP were monitored at 5- and 1-min intervals, respectively, when the rats were undisturbed or after several different types of experimental manipulations some of which are considered stressful. Cage enrichment did not significantly alter heart rate or SBP of undisturbed rats in either strain at any time during the day or night. However, activity of female SHR was increased in the afternoon and at night under enriched conditions compared with nonenriched conditions. The enrichment program did not significantly reduce heart rate or SBP responses to most acute manipulations in either strain. However, cage enrichment increased the responses to some procedures (Sprague-Dawley: handling, 1-h restraint; SHR: subcutaneous injection, tail-vein injection, handling). We conclude that a nonsocial cage enrichment program did not reduce physiologic indicators of stress in female Sprague-Dawley rats or SHR.