Effect of median eminence lesion on the hypertensive response due to acute aortic coarctation.
The present study was designed to investigate the effect of a lack of vasopressin resulting from electrolytic lesion of the median eminence of the hypothalamus on the acute 45-min aortic coarctation hypertension elicited in conscious rats by means of a pneumatic cuff placed around the aorta above the renal arteries. Forty-eight hours after lesion, aortic constriction elicited a prompt (5-min) rise in mean carotid pressure from 115 +/- 2 to 149 +/- 2 mmHg, followed by a gradual decline to 129 +/- 2 mmHg. In contrast, sham-lesioned rats exhibited a prompt hypertensive response from 118 +/- 2 to 157 +/- 2 mmHg that leveled off throughout the experiment. Lesioned rats treated with saralasin presented a blunted hypertensive response (within 125 +/- 2 to 130 +/- 2 mmHg), whereas sham-lesioned rats showed only a delay in the onset of hypertension. The hypertensive response of lesioned rats was unaffected by the vasopressin antagonist [d(CH2)5Tyr(Me)]AVP, whereas sham-lesioned rats submitted to this treatment presented a prompt rise in pressure followed by a gradual decline at the end of the experiment. Lesioned and sham-lesioned rats treated with saralasin plus vasopressin antagonist showed a blunted hypertensive response throughout the experiment. These data demonstrate that the integrity of the median eminence plays a pivotal role in the maintenance (30-45 min) of acute aortic coarctation hypertension, presumably involving the release of vasopressin from the neurohypophysis, whereas angiotensin II mainly accounts for the prompt (5-15 min) rise in pressure.
Fregoneze
J B
JB
Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
Salgado
M C
MC
Salgado
H C
HC
D000208:Acute Disease; D000818:Animals; D001017:Aortic Coarctation / Q000150:complications*; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D006973:Hypertension / Q000209:etiology*; D008297:Male; D008473:Median Eminence / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D012504:Saralasin / Q000494:pharmacology; D014667:Vasopressins / Q000037:antagonists & inhibitors
D014667:Vasopressins; D001127:Arginine Vasopressin; C025043:vasopressin, 1-(1-mercaptocyclohexaneacetic acid)-2-(O- methyl-L-tyrosine)-8-L-arginine-; D012504:Saralasin