Central serotoninergic response to orthostatic challenge in patients with neurocardiogenic syncope.
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.
Guzman
Juan Camilo
JC
Autonomic Physiology Laboratory, Research Institute, Fundacion Cardiovascular de Colombia, Bucaramanga, Santander, Colombia, Ontario, Canada.
Garcia
Ronald Gerardo
RG
Dillenburg
Rejane
R
Sieger
Federico Silva
FS
Lopez-Jaramillo
Patricio
P
Morillo
Carlos A
CA
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
D011388:Prolactin; D006854:Hydrocortisone