Circadian cortisol secretion and circadian adrenal responses to ACTH are maintained in dexamethasone suppressed capuchin monkeys (Cebus apella)

Am J Primatol. 2008 Jan;70(1):93-100. doi: 10.1002/ajp.20461.


We tested the hypothesis that the capuchin monkey adrenal (Cebus apella) gland has oscillatory properties that are independent of adrenocorticotropic hormone (ACTH) by exploring under ACTH suppression by dexamethasone: (i) maintenance of a circadian rhythm of plasma cortisol and (ii) clock time dependency of plasma cortisol response to exogenous ACTH. The capuchin monkey had a clear ACTH and plasma cortisol rhythm. Dexamethasone treatment resulted in low non-rhythmic ACTH levels and decreased cortisol to 1/10 of control values; nevertheless, the circadian rhythm of plasma cortisol persisted. We found that cortisol response to exogenous ACTH was clock time-dependent. The maximal response to ACTH occurred at the acrophase of the cortisol rhythm (0800 h). These results suggest that the capuchin monkey adrenal cortex may possess intrinsic oscillatory properties that participate in the circadian rhythm of adrenal cortisol secretion and in the circadian cortisol response to ACTH.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Glands / drug effects
  • Adrenal Glands / metabolism*
  • Adrenocorticotropic Hormone / metabolism*
  • Adrenocorticotropic Hormone / pharmacology
  • Animals
  • Cebus / physiology*
  • Circadian Rhythm / physiology*
  • Dexamethasone / pharmacology*
  • Female
  • Hydrocortisone / metabolism*
  • Male
  • Time Factors


  • Dexamethasone
  • Adrenocorticotropic Hormone
  • Hydrocortisone