cGMP-dependent and not cAMP-dependent kinase is required for adenosine-induced dilation of intracerebral arterioles.
Adenosine (ADO) is a potent cerebral vasodilator and has been proposed as a metabolic regulator of cerebral blood flow. However, the signal transduction pathway by which ADO causes vasodilation in cerebral microvessels is currently unknown. The current study was designed to investigate the role of cyclic nucleotides and cyclic nucleotide-dependent protein kinases in ADO-induced dilation of resistance-sized rat cerebral arterioles that develop spontaneous tone. Arterioles were cannulated and perfused intraluminally at constant flow (2 microl/min) and pressure (60 mm Hg). ADO (29.7 +/- 2.0%; 1 microM), CGS-21680 (16 +/- 4%, 1 microM), 8-bromo-cyclic guanosine monophosphate (8 Br-cGMP; 29.9 +/- 3.9%; 100 microM), sodium nitroprusside (SNP; 30.6 +/- 3.3%, 1 microM), cyclic guanine monophosphate-dependent protein kinase activator (Sp-8-pCPT-cGMPS, 25.9 +/- 4.2%; 10 microM), forskolin (30.5 +/- 5.9%; 0.1 microM), and pH 6.8 all produced large dilations. The selective cGMP-dependent protein kinase inhibitor, Rp-8-pCPT-cGMPS (10 microM), had no effect on resting diameter or reactivity to acidic pH, but significantly ( < 0.05) attenuated arteriolar dilations to ADO (59%, n = 8), CGS-21680 (60%, n = 4), SNP (62%, n = 3), 8 Br-cGMP (88%, n = 3), and Sp-8-pCPT-cGMPS (98%, n = 3). H8, the less-selective cyclic nucleotide-dependent protein kinase inhibitor, had similar effects as Rp-8-pCPT-cGMPS. Additionally, the inhibitor of the soluble guanylate cyclase, 1H-[1,24]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), blocked the response to SNP (70% inhibition) and significantly inhibited the ADO response (43% inhibition). In contrast, inhibition of the cyclic ADO monophosphate (cAMP)-dependent protein kinase Rp-8-CPT-cAMPS had no effect on the ADO, SNP, or pH responses, but significantly blocked forskolin-induced vasodilation (53%). It is concluded that ADO-induced vasodilation in cerebral microvessels, at least in part, involves cGMP and cGMP-dependent protein kinase, but not cAMP or cAMP-dependent kinase. Our data therefore provides a new insight into mechanisms by which ADO invokes vasodilation in cerebral microvascular arterioles.
West
G Alexander
GA
Department of Neurological Surgery, University of Washington, Seattle, Washington 98104, USA. gawest@u.washington.edu
Meno
Joseph R
JR
Nguyen
Thien-Son K
TS
Ngai
Al C
AC
Simard
J Marc
JM
Winn
H Richard
HR
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000201:enzymology; D002540:Cerebral Cortex / Q000098:blood supply* / Q000187:drug effects / Q000201:enzymology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; D000241:Adenosine