Increases in local cerebral blood flow associated with somatosensory activation are not mediated by NO.
Effects of inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME) on the increases in local cerebral blood flow (LCBF) produced in the whisker-to-barrel sensory pathway by vibrissal stimulation were studied in conscious rats with the autoradiographic iodo[14C]antipyrine method. Unilateral whisker stroking increased LCBF in the ipsilateral trigeminal spinal and principal sensory nuclei, contralateral ventral posteromedial thalamic nucleus, and contralateral somatosensory barrel cortex. Intravenous L-NAME (30 mg/kg) lowered baseline LCBF without altering the percent increases due to stimulation. Intracisternal infusions of L-NAME in doses about 10 times the molar content of free arginine in brain inhibited brain NO synthesis activity by 88%, but the percent augmentations of LCBF by stimulation remained unchanged. Chronic treatment with L-NAME (50 mg/kg ip twice daily for 4 days) inhibited NO synthase activity in brain by 84% but also failed to reduce the percent increases in LCBF due to stimulation. These results indicate that NO does not mediate the increases in LCBF associated with functional activation.
Adachi
K
K
Laboratory of Cerebral Metabolism, National Institute of Mental Health, Bethesda, Maryland 20892.
Takahashi
S
S
Melzer
P
P
Campos
K L
KL
Nelson
T
T
Kennedy
C
C
Sokoloff
L
L
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000818:Animals; D000983:Antipyrine / Q000031:analogs & derivatives; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001345:Autoradiography; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000201:enzymology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation / Q000502:physiology
D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D000983:Antipyrine; C008135:iodoantipyrine; D019331:NG-Nitroarginine Methyl Ester