Interaction between ATP-sensitive K+ channels and nitric oxide on pial arterioles in piglets.
The interaction between ATP-sensitive K+ channels (KATP) and nitric oxide (NO) was studied in pial arterioles of piglets. We examined the effects of N omega-nitro-L-arginine methyl ester (L-NAME), a general inhibitor of nitric oxide synthase (NOS), and 7-nitroindazole (7-NI), a selective inhibitor of neuronal NOS, on aprikalim-induced cerebral vasodilation. Topically applied, aprikalim, a selective activator of KATP, dilated arterioles by 11 +/- 7% at 10(-8) M and 17 +/- 6% at 10(-6) M. After L-NAME treatment (15 mg/kg, i.v.), the response was reduced (4 +/- 4% and 12 +/- 7%, respectively; n = 8, p < 0.05). Administration of 7-NI (50 mg/kg, i.p.) did not change pial arteriolar responsiveness to aprikalim. However, both L-NAME and 7-NI reduced the vasodilator responses to 10(-4) M N-methyl-D-aspartate (NMDA) (by 73% and by 36%, respectively). Furthermore, 7-NI treatment abolished the glutamate-induced dilatation of pial arterioles. Administration of L-NAME reduced the NOS activity in the cerebral cortex by 88%, whereas the reduction after the 7-NI treatment was 44%. Pre-treatment and coadministration of 10(-5) M glibenclaminde, a specific inhibitor of KATP or L-NAME administration, did not change the dilatory response to sodium nitroprusside. We conclude that NO may be involved in aprikalim-induced dilation of pial arterioles.
Bari
F
F
Department of Physiology and Pharmacology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1083, USA.
Errico
R A
RA
Louis
T M
TM
Busija
D W
DW
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000098:blood supply*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007191:Indazoles / Q000494:pharmacology; D008833:Microcirculation / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D015221:Potassium Channels / Q000378:metabolism*; D013552:Swine; D014664:Vasodilation / Q000187:drug effects
D004791:Enzyme Inhibitors; D007191:Indazoles; D015221:Potassium Channels; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; C080122:7-nitroindazole; D019331:NG-Nitroarginine Methyl Ester