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Effect of Age on Autonomic and Cardiac Responses in a Rat Stroke Model
Vladimir C. Hachinski, MD;
John X. Wilson, PhD;
Karen E. Smith, MSc;
David F. Cechetto, PhD
Arch Neurol. 1992;49(7):690-696.
Abstract
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• The cardiovascular system and its responses change with increasing age. This has seldom been considered in experimental models of stroke, although most strokes occur in the elderly. We studied 57 male Wistar rats in three age groups: 47 to 70 days old (juvenile), 110 to 152 days old (young adult), and 186 to 245 days old (mature adult), each group being subdivided into experimental and sham operation groups. All rats underwent occlusion or sham occlusion of the left middle cerebral artery and monitoring of the mean arterial blood pressure, heart rate, sympathetic nerve activity, plasma catecholamine levels, and electrocardiogram. Eight of the 12 rats in the oldest group died within 6 hours of the middle cerebral artery occlusion; of these, the youngest was 186 days old. The mature adult rats that died before completion of the experiment showed the highest level of sympathetic nerve activity and the only significant increase in the QT interval of the electrocardiogram. Following middle cerebral artery occlusion, sympathetic nerve activity increased in the young adult rats but most strikingly in the mature adult rats that died before the end of the 6-hour experiments. Plasma norepinephrine levels were significantly elevated at 4 and 6 hours after middle cerebral artery occlusion in the oldest group and only at 6 hours in the juvenile rats. The results of this study are consistent with impaired sympathetic and cardiovascular regulation in the mature adult rat. High sympathetic activity may represent one mechanism leading to fatal cardiac arrhythmias. Age-related impairment of sympathetic regulation may contribute to the higher mortality seen among elderly patients with stroke.
Author Affiliations
From the Departments of Clinical Neurological Sciences (Drs Hachinski and Cechetto) and Physiology (Drs Hachinski, Wilson, and Cechetto), University of Western Ontario, and the Stroke and Aging Research Group, The John P. Robarts Research Institute (Drs Hachinski and Cechetto and Ms Smith), London, Ontario. Dr Hachinski is a career investigator with the Heart and Stroke Foundation of Ontario, Toronto. Dr Cechetto is a scholar with the Heart and Stroke Foundation, Ottawa, Ontario.
Footnotes
Accepted for publication March 11, 1992.
Reprint requests to Department of Clinical Neurological Sciences, University Hospital, 339 Windermere Rd, London, Ontario, Canada N6A 5A5 (Dr Hachinski).
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