Sensory fibers containing vanilloid receptor-1 (VR-1) mediate spinal cord stimulation-induced vasodilation

• Published in: Brain research 2006-08, Vol.1107 (1), p.177-184
• Main Authors: Wu, Mingyuan, Komori, Naoka, Qin, Chao, Farber, Jay P., Linderoth, Bengt, Foreman, Robert D.
• Format: Article
• Language: English
• Subjects: Animals; Antidromic afferent activation; Biological and medical sciences; Blood Pressure - drug effects; Blood Pressure - physiology; Blood Pressure - radiation effects; Diterpenes - pharmacology; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Electric Stimulation - methods; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Laser-Doppler Flowmetry - methods; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Nerve Fibers - drug effects; Nerve Fibers - metabolism; Nerve Fibers - radiation effects; Neurotoxins - pharmacology; Rats; Rats, Sprague-Dawley; Regional Blood Flow - drug effects; Regional Blood Flow - physiology; Regional Blood Flow - radiation effects; Resiniferatoxin (RTX); Skin - innervation; Spinal Cord - physiology; Spinal Cord - radiation effects; Spinal cord stimulation (SCS); TRPV Cation Channels - metabolism; Vanilloid receptor type 1 (VR-1); Vasodilation; Vasodilation - physiology; Vasodilation - radiation effects; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2006.05.087

Background and aims: Spinal cord stimulation (SCS) is used to improve peripheral blood flow in selected populations of patients with ischemia of the extremities. Previous studies show that antidromic activation of sensory fibers is an important mechanism that contributes to SCS-induced vasodilation. However, the characteristics of sensory fibers involved in vasodilation are not fully known. This study investigated the contribution of vanilloid receptor type 1 (VR-1) containing fibers to SCS-induced vasodilation. Methods: A unipolar ball electrode was placed on the left dorsal column at the lumbar 2–3 spinal cord segments (L2–L3) in sodium pentobarbital anesthetized, paralyzed and ventilated rats. Cutaneous blood flows from both ipsilateral (left) and contralateral (right) hind foot pads were recorded with laser Doppler flow perfusion monitors. SCS (50 Hz; 0.2 ms) was applied through the ball electrode at 30%, 60%, 90% and 300% of motor threshold (MT). Resiniferatoxin (RTX), an ultra potent analog of capsaicin and VR-1 receptor agonist, was used to suppress the activities of VR-1 containing sensory fibers. Results: SCS at 30%, 60%, 90% and also at 300% of MT significantly increased cutaneous blood flow in the ipsilateral foot pad compared to that in the contralateral side. RTX (2 μg/kg, i.v.) significantly attenuated SCS-induced vasodilation of the ipsilateral side ( P