AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 6 1472-R1478, Copyright © 1990 by American Physiological Society

ARTICLES

Area postrema: essential for support of arterial pressure after hemorrhage in rats

K. M. Skoog, M. L. Blair, C. D. Sladek, W. M. Williams and M. L. Mangiapane
Department of Pharmacology, School of Medicine and Dentistry, University of Rochester, New York 14642.

Previous studies have indicated that the area postrema (AP) of the rat is necessary for the development of chronic angiotensin-dependent hypertension. The present study assesses the role of the AP in the maintenance of arterial pressure during hemorrhage. Sprague-Dawley rats were given sham or AP lesions 1 wk before the experiment. They were instrumented with femoral arterial and venous catheters 2 days before the experiment. On the day of the experiment, base-line mean arterial pressure (MAP) was measured for 1 h before hemorrhage. During the following 45 min, each rat was subjected to one 7-ml/kg hemorrhage every 15 min for a total of three hemorrhages. MAP was monitored by computerized data acquisition. As shown previously, MAP was slightly but significantly lower in AP-lesion rats compared with sham-lesion rats before the hemorrhage procedure. In AP-lesion rats, hemorrhage resulted in a significantly greater fall in arterial pressure than in sham-lesion rats. In spite of larger drops in pressure in AP-lesion rats, hemorrhage caused equivalent increases in plasma renin and vasopressin in both groups. In AP-lesion rats compared with sham-lesion rats, significant bradycardia was present before hemorrhage. Hemorrhage caused bradycardia in both sham- and AP-lesion rats relative to the prehemorrhage heart rates, but AP-lesion rats showed greater bradycardia than did sham-lesion rats during every time period. We conclude that the AP may play an important role in the defense of arterial pressure against hemorrhage.

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