Effects of Spinal Cord Stimulation with different frequencies on blood flow in the rat hind paw

Abstract

Spinal cord stimulation (SCS) at a frequency of ∼50 Hz is used to improve peripheral blood flow. However, it is unclear whether SCS at higher frequencies induces further increases vasodilation and enhances clinical efficacy. This study investigated effects of SCS at different frequencies on peripheral vasodilation. SCS was setup at the lumbar 2–3 spinal cord segments in rats. Cutaneous blood flows from both ipsilateral and contralateral hind foot pads were recorded with laser Doppler flow perfusion monitors. SCS at frequencies of 50, 200 or 500 Hz was applied through the ball electrode at 30%, 60% and 90% of motor threshold (MT). Resiniferatoxin (RTX), an ultra potent analog of capsaicin, was applied to block the transient receptor potential vanilloid receptor (TRPV1); Furthermore, calcitonin gene related peptide (CGRP) 8–37, a CGRP‐1 receptor blocker, was used to elucidate mechanisms of SCS vasodilation at a high frequency. SCS applied with the three frequencies produced similar MT. SCS at the frequency of 500 Hz induced a higher increase of cutaneous blood flow and decreased vascular resistance compared to that with the frequency of 50 and 200 Hz (P<0.05). RTX (2 μg/Kg. i.v.) as well as CGRP8–37 (2.37 mg/Kg. i.v.) significantly reduced SCS‐induced vasodilation at this high frequency (500 Hz) (P<0.05). In conclusion, SCS at a high frequency significantly increased SCS‐induced vasodilation effect without influencing the MT. Furthermore, effects of SCS at high frequency seem to be predominantly mediated via activation of TRPV1 containing fibers including a release of CGRP.