| Summary: | <p>Abstract</p> <p>Background</p> <p>Specific alternation of rhythm in temperature (SART)-stressed rats, an animal model of autonomic imbalance, exhibit low blood pressure and tachycardia during consciousness and under anesthesia. In addition, these rats easily develop orthostatic hypotension (OH) as a response to postural manipulation. Hence, we studied the influence of the adrenalin α<sub>1</sub>-receptor agonist phenylephrine on stress-induced OH in SART-stressed rats and unstressed rats.</p> <p>Methods</p> <p>Male Wistar rats weighing 250-300 g were used. Rats were fixed in the supine position under urethane anesthesia. Blood pressure was directly measured from the left common carotid artery and ECG was recorded simultaneously.</p> <p>Results</p> <p>The maximum decrease in blood pressure and the area under the blood pressure-time curve were both large, while the %reflex was small in the SART-stressed rats compared with unstressed rats. In the SART-stressed rats, prolonged intravenous administration of phenylephrine reduced OH at a dose that barely affected unstressed rats.</p> <p>Conclusion</p> <p>The results suggested that sympathetic dysfunction is a factor underlying SART stress-induced OH.</p>
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