Blood-to-cerebrospinal fluid barrier for cyclic adenosine monophosphate in man

A definite blood to lumbar CSF barrier for cyclic adenosine monophosphate (cAMP) exists in man under physiologic conditions. Lumbar CSF cAMP level remained unchanged, while the CSF glucose level rose significantly after a glucagon hydrochloride infusion that caused a 40-fold increase in the plasma cAMP level.