title: The role of adenosine in the vascular adaptation of neonatal cerebral blood flow during hypotension.
abstract: This study investigated the potential role of adenosine in cerebral blood flow (CBF) regulation in the neonate during moderate and severe hypotension. Experiments were done in anesthetized, 1- to 3-day-old piglets. Regional CBF (determined by radiolabeled microsphere technique) and cerebral metabolic rate for O2 (CMRO2) were measured (a) during normotension and (b) during a 3-min period of moderate (58 +/- 9 mm Hg) or severe (36 +/- 7 mm Hg) hypotension produced by the inflation of a balloon catheter placed in the aortic root. Measurements of CBF and CMRO2 were performed successively after intracerebroventricular (i.c.v.) injections of vehicle (n = 17), the adenosine receptor blocker 8-phenyltheophylline (8-PT, 10 micrograms, n = 14), and the A2-receptor agonist 5'-N-(ethylcarboxamide)adenosine (NECA, 2 ng, n = 8). After i.c.v. administration of vehicle, none of the parameters studied was significantly altered by moderate hypotension, but severe hypotension decreased the total CBF (mean +/- SD) from 86 +/- 24 to 40 +/- 15 ml min-1 100 g-1 and CMRO2 from 3.2 +/- 0.8 to 1.8 +/- 1.0 ml min-1 100 g-1 (p less than 0.05). Administration of 8-PT did not alter these parameters during normotension, but significantly decreased CBF during moderate hypotension compared to postvehicle values (53 +/- 11 versus 81 +/- 12 ml min-1 100 g-1, p less than 0.05). This loss of autoregulation was completely reversed by NECA. During severe hypotension, 8-PT altered the CBF redistribution towards the brainstem.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Developmental Pharmacology and Perinatal Research Unit, McGill University, Montreal, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Laudignon
authors.forename: K
authors.initials: K
authors.lastname: Beharry
authors.forename: E
authors.initials: E
authors.lastname: Farri
authors.forename: J V
authors.initials: JV
authors.lastname: Aranda
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000134:cerebrospinal fluid / Q000494:pharmacology / Q000502:physiology*; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001783:Blood Flow Velocity; D001921:Brain / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D007022:Hypotension / Q000503:physiopathology*; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000134:cerebrospinal fluid; D007288:Inosine / Q000134:cerebrospinal fluid; D010100:Oxygen / Q000378:metabolism; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology; D013552:Swine; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014655:Vascular Resistance / Q000502:physiology
chemical_list: D007042:Hypoxanthines; D011983:Receptors, Purinergic; D019271:Hypoxanthine; D019830:Adenosine-5'-(N-ethylcarboxamide); D007288:Inosine; D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine; D010100:Oxygen