Objectives: In our previous study, we have demonstrated blunt beta-adrenergic receptor (BAR) function in fibromyalgia patients (Maekawa et al., Journal of Pain, in press). The aim of this study was to make clear whether the same phenomenon could be observed in localized myalgia subjects. Methods: Eleven subjects with chronic localized myalgia (myalgia, male/female: 5/6, mean age: 22.7±1.2 yrs) and twenty-one asymptomatic subjects (control, male/female: 10/11, mean age: 22.6±1.2 yrs) participated in this study. Selection criteria for myalgia subjects were: 1) pain in the shoulder/neck/orofacial region at least once a week for six months; 2) more than three tender points in 30 examined palpation points. Exclusion criteria were: 1) history of joint or neurological problem; 2) in conditions which affect the BAR function (such as asthma, diabetes, heart disease, hypertension); 3) smokers; and 4) history of fibromyalgia. Thirty cc peripheral blood samples were drawn from subjects' anterocubital vein. Lymphocyte cells were isolated from the total blood by using the Ficoll-Hypaque gradient technique. Aliquots of 5x10⁶ cells were incubated for 5 min with or without beta-agonist isoproterenol (ISO) in 5 different concentrations (10^-3M to 10^-7M). Basal and stimulated levels of intracellular BAR second messenger, cyclic adenosine monophosphate (cAMP) were measured by an enzyme immunoassay kit (cAMP EIA system, Amersham, England). Two-way repeated measure ANOVA with two predictors (group difference and ISO concentration) were utilized. Results: The mean basal cAMP levels (myalgia: 0.33±0.02 pmol/5x10⁶cells; control: 0.43±0.10 pmol/5x10⁶cells) were almost identical between the groups. ISO-stimulated mean cAMP levels significantly increased dose-dependently in both groups (main effect for ISO concentration: p<0.001), while mean group difference in the ISO-stimulated cAMP levels was not significant (main effect for group difference: p=0.909). Conclusions: These results suggest that BAR function is not disturbed in localized myalgia subjects, which indirectly supports the notion that localized myalgia is pathophysiologically different from fibromyalgia. (Grant-in-aid #12671883 in Japan)