Impaired functional recovery after stroke in the stroke-prone spontaneously hypertensive rat

Background and Purpose - To identify if the stroke-prone spontaneously hypertensive rat (SHRSP) exhibits impaired functional recovery after stroke compared with its normotensive reference strain, the Wistar Kyoto rat (WKY). Methods - In study 1, a 2-mm distal middle cerebral artery occlusion ( middle cerebral artery occlusion) was performed in both strains and recovery assessed using a 33-point neurological score. Because SHRSPs displayed much larger infarcts than WKYs, study 2 and study 3 involved extending the length of middle cerebral artery (MCA) occlusion in the WKY to increase the volume and distribution of infarction to comparable levels with SHRSP. Animals were assessed with the neurological score, tapered beam walk, and cylinder tests. Results - In study 1, infarct volume ( expressed as a percent of contralateral hemisphere) was WKY 13.1 +/- 3% and SHRSP 19.8 +/- 1%. Initial neurological deficit was greater ( WKY 25 +/- 1, SHRSP 22 +/- 1, out of a possible 33) and subsequent recovery was poorer in SHRSP. In studies 2 and 3, infarct volume and distribution ( study 2, WKY 21.8 +/- 1.3%, SHRSP 22.9 +/- 3%; study 3, WKY 17.2 +/- 2%, SHRSP 16.5 +/- 3%) and initial neurological deficit at 2 hours after middle cerebral artery occlusion ( study 2 WKY 23 +/- 1, SHRSP 22 +/- 2; study 3 WKY 25 +/- 1 and SHRSP 23 +/- 1; mean +/- SEM) were comparable between strains. However, whereas WKY recovered toward normal scores, SHRSP scored significantly lower 2 weeks ( study 2) and 4 weeks ( study 3) after middle cerebral artery occlusion. Beam walk data revealed long-term impairment in SHRSP contralateral limb use, compared with WKY, at days 3, 7, and 28 ( P < 0.05). Conclusions - SHRSP exhibit impaired functional recovery after stroke compared with WKY.