Chronic, severe hypertension does not impair spatial learning and memory in Sprague-Dawley rats

This study tested the hypothesis that long-term hypertension impairs spatia l learning and memory in rats. In CF 6-wk-old Sprague-Dawley rats, chronic hypertension was induced by placing one of three sizes of stainless steel c lips around the descending aorta (above the renal artery), resulting in a 2 0-80-mm Hg increase of arterial pressure in all arteries above the clip, th at is, the upper trunk and head. Ten months later, the rats R-ere tested fo r 5 d in a repeated-acquisition water maze task, and on the fifth day, they were tested in a probe trial; that is, there was no escape platform presen t. ht the end of the testing period, the nonsurgical and sham control group s had similar final escape latencies (16 +/- 4 sec and 23 +/- 9 sec, respec tively) that were not significantly different from those of the three hyper tensive groups. Rats with mild hypertension (140-160 mm Hg) had a final esc ape latency of 25 +/- 6 sec, whereas severely hypertensive rats (170-199 mm Hg) had a final escape latency of 21 +/- 7 sec and extremely hypertensive rats (>200 Hg) had a final escape latency of 19 +/- 5 sec. All five groups also displayed a similar preference for the correct quadrant in the probe t rial. Together, these data suggest that sustained, severe hypertension for over 10 mo is not sufficient to impair spatial learning and memory deficits in otherwise normal rats.