The area postrema plays no role in the pressor action of angiotensin in the rat

The area postrema has been shown to have a major role in mediating the pressor effects of peripheral angiotensin in the dog, cat, and rabbit. The purpose of this study was to ascertain the function of the medullary circumventricular structure in the conscious rat. The pressor potency of angiotensin administered into the vertebral and carotid arteries was compared with intra-aortic infusions of angiotensin. Although no difference in pressor activity of angiotensin could be detected between intraaortic and intravertebral administration, greater sensitivity was observed during intracarotid infusion. No difference in the course of one-kidney renal hypertension was observed between sham-lesioned rats and animals with an area postrema lesion. In addition, lesioned and sham-lesioned animals showed equivalent responses to graded doses of angiotensin administered either intravenously or into the lateral ventricle. It was concluded that in the rat the area postrema plays no role in mediating the central nervous system actions of angiotensin whether the peptide reaches the brain via the blood or the cerebrospinal fluid.