Dilatation of cerebral parenchymal vessels mediated by angiotensin type 1 receptor in cats.
We report the effects of angiotensin II (ANG-II), as well as angiotensin II type 1 (AT1) and type 2 receptor antagonists (CV-11974 and PD-123319, respectively) on the cerebral parenchymal microvessels in cats using the photoelectric method. ANG-II continuously and dose-dependently increased the cerebral blood volume (CBV) for 15 min. Maximum CBV increases were +0.36+or-0.11 vol% for 0.01 nmol/kg (P<0.05), +0.51+or-0.24 vol% for 0.1 nmol/kg (P<0.05), +1.87+or-0.55 vol% for 1 nmol/kg (P<0.05), and +2.14+or-0.77 vol% for 10 nmol/kg (P<0.05). Systemic arterial blood pressure increased at only 1 min following ANG-II infusion (1 and 10 nmol/kg). CV-11974 and PD-123319 per se did not change the resting CBV. CV-11974 completely inhibited the vasodilatory action of ANG-II, however, PD-123319 did not block it. We conclude that ANG-II directly dilates the parenchymal vessels through the AT1 receptor without increasing systemic blood pressure, and that intrinsic ANG-II may not be associated with maintenance of resting vascular tone.
Takao
Masaki
M
Department of Neurology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. msktakao@aol.com
Kobari
Masahiro
M
Tanahashi
Norio
N
Tomita
Minoru
M
Yokoyama
Masako
M
Tomita
Yutaka
Y
Otomo
Manabu
M
Inoue
Koji
K
Fukuuchi
Yasuo
Y
D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001562:Benzimidazoles / Q000494:pharmacology; D001713:Biphenyl Compounds; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D002536:Cerebral Arteries / Q000187:drug effects / Q000378:metabolism*; D002540:Cerebral Cortex / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000819:agonists / Q000378:metabolism*; D013777:Tetrazoles / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D057911:Angiotensin Receptor Antagonists; D000959:Antihypertensive Agents; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D007093:Imidazoles; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D013777:Tetrazoles; D000804:Angiotensin II; C073402:PD 123319; C081643:candesartan