Effect of Propranolol on the Autonomic Nervous System and Muscle Pain

Inclusion Criteria: * Meet Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) for myofascial TMD diagnosis corresponding to group 1a or 1b * Characteristic Pain Intensity (CPI) more than or equal to 20 (Axe II, RDC/TMD questionnaire) * Women of childbearing potential must use adequate contraception * Signed consent statement Exclusion Criteria: * Other acute pain cause such as acute toothache or a pain condition the investigator estimates to be contraindicated for participation in the experiment * Recognized existing malignancy or within last 5 years * Known HIV * Abuse of drugs including alcohol * Recognized Raynaud's syndrome * Former sympathectomy * Known cardiovascular disease including abnormal EKG and blood pressure (ECG-12 is recorded before the first trial session and assessed by the physician) * Recognized lung insufficience, including bronchial asthma * Known severe hepatic or renal dysfunction * Known diabetes mellitus * Known severe depression * Pregnancy (tests performed in both sessions 1 and 2 before the start of a session) * Fertility Treatment * Lactation * Post-menopausal * Previous adverse reaction when taking beta-blocker, including hypersensitivity to propranolol or to any of the excipients * Patients who can not read and understand the written information * Patients who can not follow the protocol * Patients who do not agree to comply with the requirements for participation in both studies regarding food intake, physical activity, etc.