Role of sensory C fibers in hypoxia/reoxygenation-impaired myogenic constriction of cerebral arteries.
OBJECTIVE
Hypoxia/reoxygenation (H/R) associated with extracorporeal membrane oxygenation disrupts cerebral autoregulation. However, the underlying mechanisms remain poorly understood. The present study was designed to investigate the role of sensory C-fibers in myogenic responsiveness of cerebral arteries.


METHODS
Arterial diameter and intraluminal pressure were simultaneously measured in vitro on rat posterior cerebral arteries.


RESULTS
Cerebral arteries constricted in response to graded increase in intraluminal pressure (20-100 mmHg, in 20 mmHg increments). In vitro C-fiber desensitization with capsaicin (1 micromol/l, 20 minutes) significantly suppressed myogenic constriction by over 50%, but did not affect 5-hydroxytryptamine (0.01-10 micromol/l) and KCl (120 mmol/l)-induced constriction. Capsazepine (5 micromol/l, 30 minutes), a selective blocker of neuronal vanilloid receptor TRPV1, had similar inhibitory effect on cerebral myogenic constriction to elevated pressure. Cerebral myogenic constriction was significantly attenuated by H/R; the impairment by H/R was further enhanced after C-fiber desensitization (except at a pressure level of 100 mmHg).


CONCLUSIONS
These findings indicate that C-fiber activity contributes to myogenic constriction of cerebral arteries under normal and H/R conditions. H/R-impaired myogenic responsiveness is exaggerated by C-fiber dysfunction. These results raise the possibility that therapeutic strategies directed toward preserving C-fiber nerve endings or supplying its constituent neuropeptides could be developed.
Xie
Hui
H
Department of Neonatology, Children's Research Institute, Children's National Medical Center, The George Washington University, Washington, DC, USA.
Ray
Patricio E
PE
Short
Billie Lou
BL
D000818:Animals; D001794:Blood Pressure; D002539:Cerebral Arterial Diseases / Q000473:pathology / Q000503:physiopathology*; D002536:Cerebral Arteries / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology; D002534:Hypoxia, Brain / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D009929:Organ Size; D010100:Oxygen / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D018377:Neurotransmitter Agents; D014662:Vasoconstrictor Agents; D010100:Oxygen