Hypothalamic blood flow autoregulation remains unaltered following surgical and pharmacological blockade of central vasopressin.
Experiments were carried out in urethane anaesthetized, ventilated rats to determine if brain arginine-vasopressin (AVP) plays a physiological role in cerebral blood flow autoregulation. Autoregulation was tested by determining local hypothalamic blood flow in the mediobasal hypothalamic area (HBF; H2-gas clearance technique) during consecutive stepwise lowering of systemic mean arterial pressure to 80, 60 and 40 mm Hg, by hemorrhage. Endogenous AVP was blocked by transecting the rostral, lateral and dorsal neuronal connections of the hypothalamus (including the median eminence) from all major brain areas, by bilateral transection of the vasopressin-containing fibres in the hypothalamo-hypophyseal tract to the median eminence at the level of the lateral retrochiasmatic area (RCAL), and finally by intracerebroventricular (i.c.v.) administration of an AVP antagonist, d(CH2)5Tyr(Me)AVP (AAVP). Significant increases of daily water intake indicated impaired vasopressin release following both types of surgical transection. Resting HBF was significantly elevated both after surgical isolation of the hypothalamus and after 10 ng AAVP administration compared to controls. Blood flow autoregulation in the hypothalamic region was seriously impaired following surgical isolation of the hypothalamus. However, HBF autoregulation remained just as effective as that of the control rats following either selective bilateral transection of the vasopressin pathways or following AAVP treatment. The present data indicate that AVP may play a role in the control of resting hypothalamic blood flow, but does not support a role of AVP in HBF autoregulatory mechanisms.
Sandor
P
P
Marion Merrell Dow Research Institute, Strasbourg, France.
Petty
M
M
de Jong
W
W
Palkovits
M
M
de Wied
D
D
D000818:Animals; D001127:Arginine Vasopressin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects*; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis; D007031:Hypothalamus / Q000098:blood supply*; D007276:Injections, Intraventricular; D008297:Male; D008473:Median Eminence / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
D001127:Arginine Vasopressin; C025043:vasopressin, 1-(1-mercaptocyclohexaneacetic acid)-2-(O- methyl-L-tyrosine)-8-L-arginine-