Nitric oxide inhibition by L-NAME but not 7-NI induces a transient increase in cortical cerebral blood flow and affects the cerebrovasodilation induced by TRH.
The tripeptide thyrotropin releasing hormone (TRH) has multiple interesting and complex physiological effects. One of these is the cerebrovasodilating effect, which has been described under several different conditions. The final mechanism for this effect is unknown. In the present study, we found an initial atropine-resistant cerebral vasodilation (24%) elicited by the NOS inhibitor L-NAME in the rat. D-NAME and 7-NI did not produce this effect. TRH (300 microg kg(-1), i.v.) induced an increase in cerebral blood flow by 62%. L-NAME reduced this effect significantly. The cerebrovasodilating mechanism of TRH, at least in part, is endothelial NO dependent as the neuronal 7-NI NOS inhibitor does not affect the TRH response.
Koskinen
Lars-Owe D
LO
Department of Pharmacology and Clinical Neuroscience, Division of Neurosurgery, Umeå University Hospital, SE-901 85 Umeå, Sweden. lars-owe.koskinen@neuro.umu.se
Koch
Mona L
ML
D000818:Animals; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007191:Indazoles / Q000494:pharmacology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000378:metabolism / Q000494:pharmacology*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
D004791:Enzyme Inhibitors; D007191:Indazoles; D010455:Peptides; D009569:Nitric Oxide; D013973:Thyrotropin-Releasing Hormone; D019001:Nitric Oxide Synthase; C080122:7-nitroindazole; D019331:NG-Nitroarginine Methyl Ester