ACTH in plasma and CSF in the rhesus monkey.

Adrenocorticotrophic hormone (ACTH) and other biosynthetically related peptides are found both in the brain and peripherally, but the function and regulation of these substances differ in the brain and in the periphery. It has been suggested that measurement of peptide hormones in the cerebrospinal fluid (CSF) might provide information relevant to the diagnosis and pathophysiology of neurological and psychiatric illnesses. We report experiments using a rhesus monkey model to evaluate parameters affecting CSF ACTH concentrations. We found that CSF ACTH concentrations follow a diurnal rhythm that is markedly different from that in plasma, concentrations of ACTH in monkey CSF, but not in plasma, increased significantly after 4 days of social separation, and CSF ACTH concentrations did not change after hypophysectomy. These results suggest that CSF ACTH concentrations reflect the activity of brain and not peripheral ACTH systems.