CARDIOVASCULAR CHANGES DURING FOCAL CEREBRAL-ISCHEMIA IN RATS

Background and Purpose: Recent studies have suggested that cerebral infarction influences autonomic activity and way contribute to sudden death. The goal of this study was to examine effects of focal cerebral infarction on mean arterial pressure and heart rate. Methods: Halothane-anesthetized rats were assigned to two groups: stroke (n = 10), in which the middle cerebral artery or an adjacent vessel was embolized with a silicone cylinder, and sham (n = 8), in which rats were sham embolized (saline). Arterial pressure and heart rate were measured for 90 minutes and again 24 hours after vascular occlusion. A change in electroencephalographic amplitude of -45% after embolization was used to determine if a significant degree of infarction was present. Results: Vascular occlusion produced a significant increase in mean arterial pressure at 10, 60, and 90 minutes (p<0.05). Changes in heart rate were significantly greater (p<0.05) than in sham-treated rats at 10 and 30 minutes after embolization. In contrast, mean arterial pressure and heart rate measured 24 hours after embolization were similar in both groups. Anatomic analysis of the infarcted areas demonstrated that either insular cortex or amygdala was affected in all embolized rats. Conclusions: This study indicates that cerebral infarction produces a transient elevation of mean arterial pressure and heart rate. However, within 24 hours both parameters returned to preinfarcted levels. Our findings are consistent with clinical reports that indicate that mean arterial pressure and heart rate of stroke patients are similar to those of other groups when they are admitted to the hospital, although other cardiovascular parameters are greatly altered.