Area postrema: essential for support of arterial pressure after hemorrhage in rats.
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.
Skoog
K M
KM
Department of Pharmacology, School of Medicine and Dentistry, University of Rochester, New York 14642.
Blair
M L
ML
Sladek
C D
CD
Williams
W M
WM
Mangiapane
M L
ML
D000818:Animals; D001794:Blood Pressure; D001810:Blood Volume; D002552:Cerebral Ventricles; D006470:Hemorrhage / Q000097:blood / Q000503:physiopathology*; D008297:Male; D008526:Medulla Oblongata / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood; D013997:Time Factors; D014667:Vasopressins / Q000097:blood
D014667:Vasopressins; D012083:Renin