Intravenous beta-endorphin administration fails to alter hypothalamic blood flow in rats expressing normal or reduced nitric oxide synthase activity.
beta-Endorphin (beta-END) significantly contributes to the maintenance of hypothalamic blood flow (HBF) autoregulation during hemorrhagic hypotension in rats. Recently, several natural and synthetic opioid peptides were reported to induce nitric oxide (NO)-mediated dilation in the cerebrovascular bed. In the present study, the effect of beta-END was studied on HBF and hypothalamic vascular resistance (HVR) in vehicle-treated control rats and in rats after the pharmacological inhibition of the NO synthesis by chronic oral application of NG-nitro-L-arginine methyl ester. Intravenous beta-END administration failed to alter HBF or HVR either in control or in NO-blocked animals, and its transient hypotensive effect was not inhibited by NO blockade, indicating that beta-END may not have NO-mediated vasodilator effect in the hypothalamic or in the systemic circulation.
Benyó
Z
Z
Experimental Research Department, Semmelweis University of Medicine, Budapest, Hungary.
Szabó
C
C
Velkei
M H
MH
Bohus
B
B
Wahl
M
M
Sándor
P
P
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002245:Carbon Dioxide / Q000097:blood; D006339:Heart Rate / Q000187:drug effects*; D006454:Hemoglobins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007031:Hypothalamus / Q000098:blood supply*; D007275:Injections, Intravenous; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects*; D001615:beta-Endorphin / Q000008:administration & dosage / Q000494:pharmacology*
D006454:Hemoglobins; D002245:Carbon Dioxide; D001615:beta-Endorphin; D019001:Nitric Oxide Synthase; D010100:Oxygen; D019331:NG-Nitroarginine Methyl Ester