title: Central serotoninergic response to orthostatic challenge in patients with neurocardiogenic syncope.
abstract: OBJECTIVE
  To determine whether central serotoninergic system activity is impaired by orthostatic challenge in patients with neurocardiogenic syncope (NCS).
  
  
  RESULTS
  Thirty-five [mean age: 24 (SD): 6 years] patients with a clinical history of NCS and positive head-up tilt test and 35 age-matched healthy volunteers (CON = 25+/-5 years) with negative response were studied. Overnight dexamethasone suppression test (DST) (1.5 mg given at 11 p.m.) was performed to assess the sensitivity of the hypothalamic-pituitary-adrenal axis by measuring next day cortisol (microg/dL) at 8 a.m. and 4 p.m. Cardiac autonomic function, cortisol, and prolactin (ng/dL) were also determined at baseline supine (BAS) and after 5, 10, and 15 min of orthostatic stress (OS) at 60 degrees . No significant differences were observed in cortisol plasma levels after the DST: CON = 0.6+/-0.6 microg/dL vs. NCS = 0.6+/-0.5; P = 0.7. Cardiac autonomic function, cortisol, and prolactin responses were similar in both study groups (CON vs. NCS; P > 0.05) during BAS: cortisol = 8.6+/-4 vs.8.7+/-4 microg/dL and prolactin = 16.8+/-9 vs. 16.8+/-9 ng/dL; OS-5: cortisol = 8.7+/-5 vs. 8.5+/-4 microg/dL and prolactin = 16.9+/-9 vs. 15.8+/-9 ng/dL; OS-10: cortisol = 8.5+/-5 vs. 8.1+/-3 microg/dL; prolactin = 16.2+/-9 vs. 15.8+/-9 ng/dL, and OS-15: cortisol = 9.0+/-5 vs. 8.4+/-4 microg/dL; prolactin = 17.1+/-9 vs. 15.5+/-9 ng/dL.
  
  
  CONCLUSIONS
  Central serotoninergic response during orthostatic challenge was not impaired in patients with recurrent NCS. These findings suggest that the activation of the hypothalamic-pituitary-adrenal axis is not altered in patients with recurrent NCS.
authors.affiliation: Autonomic Physiology Laboratory, Research Institute, Fundacion Cardiovascular de Colombia, Bucaramanga, Santander, Colombia, Ontario, Canada.
authors.forename: Juan Camilo
authors.initials: JC
authors.lastname: Guzman
authors.forename: Ronald Gerardo
authors.initials: RG
authors.lastname: Garcia
authors.forename: Rejane
authors.initials: R
authors.lastname: Dillenburg
authors.forename: Federico Silva
authors.initials: FS
authors.lastname: Sieger
authors.forename: Patricio
authors.initials: P
authors.lastname: Lopez-Jaramillo
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Morillo
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004562:Electrocardiography; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D011388:Prolactin / Q000097:blood*; D018709:Statistics, Nonparametric; D019462:Syncope, Vasovagal / Q000097:blood* / Q000503:physiopathology; D018667:Tilt-Table Test
chemical_list: D011388:Prolactin; D006854:Hydrocortisone