Immediate effects of spinal manipulation on nitric oxide, substance Pand pain perception

Abstract

Previous studies have analyzed the effects of spinal manipulation on pain sensitivity by using severalsensory modalities, but to our knowledge, no studies have focused on serum biomarkers involved in thenociceptive pathway after spinal manipulation. Our objectives were to determine the immediate effect ofcervical and dorsal manipulation over the production of nitric oxide and substance P, and establishingtheir relationship with changes in pressure pain thresholds in asymptomatic subjects. In this single-blindrandomized controlled trial, 30 asymptomatic subjects (16 men) were randomly distributed into 3groups (n¼10 per group): control, cervical and dorsal manipulation groups. Blood samples wereextracted to obtain serum. ELISA assay for substance P and chemiluminescence analysis for nitric oxidedetermination were performed. Pressure pain thresholds were measured with a pressure algometer atthe C5eC6 joint, the lateral epicondyle and the tibialis anterior muscle. Outcome measures were ob-tained before intervention, just after intervention and 2 h after intervention. Our results indicated anincrease in substance P plasma level in the cervical manipulation group (70.55%) when compared withother groups (p<0.05). This group also showed an elevation in the pressure pain threshold at C5eC6(26.75%) and lateral epicondyle level (21.63%) immediately after the intervention (p<0.05). No changesin nitric oxide production were observed. In conclusion, mechanical stimulus provided by cervicalmanipulation increases substance P levels and pressure pain threshold but does not change nitric oxideconcentrations. Part of the hypoalgesic effect of spinal manipulation may be due to the action of sub-stance P.