title: Hypothalamic-pituitary-adrenal axis function following a 35% CO2 inhalation in healthy volunteers.
abstract: BACKGROUND
  The hypothalamic-pituitary-adrenal axis (HPA axis) is a central component of the brain's neuroendocrine response to stress. The extent of increase in cortisol secretion, provides an index of the HPA axis activity, and in this way, objectively reflects perceived stress. In healthy subjects, the 35% CO(2) inhalation does hardly induce stress, as expressed in anxiety. However, inconsistent results have been found in studies investigating the cortisol response following CO(2) inhalation. Clarity has to be reached about the normal reaction to this challenge, especially because this model is still a very valuable method to study central aspects of panic.
  
  
  OBJECTIVE
  The present study aimed to test the hypothesis that a single breath of 35% CO(2) would not induce cortisol release in healthy volunteers.
  
  
  METHODS
  In the current study, 20 healthy subjects underwent both a 35% CO(2) and a placebo inhalation in a randomised, single blind fashion. Cortisol levels were determined in saliva samples, taken at regular intervals.
  
  
  RESULTS
  No differences were found between the CO(2) and the placebo condition. In both conditions a significant time effect was found, which can be subscribed to normal variation in the circadian rhythm. Furthermore, only modest subjective anxiety scores were found in the CO(2) condition.
  
  
  CONCLUSIONS
  These results provide biological evidence for the hypothesis that healthy subjects are not affected by the 35% CO(2) challenge in a clinically significant way. Characteristic, PD patients react much stronger to the inhalation. Thus, in addition to psychological parameters, healthy subjects also constitute an ideal comparison group with regard to endocrinological parameters.
authors.affiliation: Department of Psychiatry and Neuropsychology and Vijverdal Academic Anxiety Center, Maastricht University, P.O. Box 88, 6200 AB Maastricht, The Netherlands.
authors.forename: Marlies A
authors.initials: MA
authors.lastname: van Duinen
authors.forename: Koen R J
authors.initials: KR
authors.lastname: Schruers
authors.forename: Erika
authors.initials: E
authors.lastname: Jaegers
authors.forename: Michael
authors.initials: M
authors.lastname: Maes
authors.forename: Eric J L
authors.initials: EJ
authors.lastname: Griez
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D002245:Carbon Dioxide / Q000008:administration & dosage* / Q000494:pharmacology; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D010913:Pituitary-Adrenal System / Q000187:drug effects*; D010919:Placebos / Q000008:administration & dosage; D011897:Random Allocation; D012463:Saliva / Q000187:drug effects / Q000378:metabolism; D012737:Sex Factors; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D010919:Placebos; D002245:Carbon Dioxide; D006854:Hydrocortisone