title: Experimental human muscle pain and muscular hyperalgesia induced by combinations of serotonin and bradykinin.
abstract: In the present study, we assessed the muscle pain and possible development of muscular hyperalgesia to mechanical stimuli after two subsequent intramuscular infusions of serotonin (5-HT) and bradykinin (BKN). The pain intensity after the infusions was continuously scored on a visual analogue scale (VAS). The subjects drew the distribution of the pain areas on a map. Pressure pain thresholds (PPTs) and suprapressure pain thresholds (SPPTs) stimulations as 150% of the pre-infusion PPTs were assessed with a pressure algometer at the injection site (10 cm below the patella), at the ankle, and at the contralateral leg and ankle. Skin sensibility was assessed with a Von Frey hair at the same sites. This was done before and after an infusion into the tibialis anterior (TA) muscle on the right leg in ten volunteers. The first infusion in each combination was either serotonin (20 nmol) or isotonic saline (NaCl 0.9%). The second infusion was bradykinin (5 or 10 nmol) or isotonic saline. The two infusions were given over 20 s and separated by 3 min. The isotonic saline followed by BKN did not induce muscle pain or muscular hyperalgesia. However, the combination of 5-HT and BKN (10 nmol) produced: (1) significantly higher VAS scores (P < 0.05) compared with all other combinations; (2) significantly longer pain offset (P < 0.05) compared with the combinations of isotonic saline and BKN; (3) significantly lower PPTs at 5, 20, and 40 min post-infusion (P < 0.05) compared with baseline PPT and PPTs after all other combinations. Cutaneous sensibility to mechanical stimuli and SPPTs were not affected by any of the combinations. The combinations of serotonin and bradykinin produce experimental muscle pain and muscular hyperalgesia to mechanical stimuli. Pre-treatment with serotonin may enhance the effect of bradykinin in the generation of muscle pain and muscular hyperalgesia in humans.
authors.affiliation: Center for Sensory-Motor Interaction, Laboratory for Experimental Pain Research, Aalborg University, Fredrik Bajers Vej 7D-3, DK-9220 Aalborg E, Denmark Department of Prosthetic Dentistry and Stomatognathic Physiology, Orofacial Pain Clinic, Royal Dental College, Aarhus University, Aarhus, Denmark Department of Gastroenterology, Aalborg Hospital, Aalborg, Denmark Department of Neurology and Danish Pain Research Centre, Aarhus University, Aarhus, Denmark.
authors.forename: Victor
authors.initials: V
authors.lastname: Babenko
authors.forename: Thomas
authors.initials: T
authors.lastname: Graven-Nielsen
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
authors.forename: Asbjørn Mohr
authors.initials: AM
authors.lastname: Drewes
authors.forename: Troels Staehelin
authors.initials: TS
authors.lastname: Jensen
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001920:Bradykinin / Q000494:pharmacology*; D006801:Humans; D006930:Hyperalgesia / Q000139:chemically induced*; D007263:Infusions, Parenteral; D008297:Male; D009135:Muscular Diseases / Q000139:chemically induced*; D010146:Pain / Q000139:chemically induced*; D010147:Pain Measurement; D012701:Serotonin / Q000494:pharmacology*; D013314:Stress, Mechanical
chemical_list: D012701:Serotonin; D001920:Bradykinin