Studies on cyclic AMP in different compartments of cerebrospinal fluid.

Adenosine 3', 5'-monophosphate (cAMP) was measured in the CSF of 42 patients undergoing radiological investigation, neurosurgical procedures, or investigation of hepatic coma. The concentration of cAMP was significantly higher in ventricular CSF than in lumbar CSF. Premedication with pentobarbitone plus promethazine increased cAMP in lumbar CSF. There was no difference in cAMP concentration in lumbar CSF obtained before or after injection of air or after the administration of diazepam during lumbar pneumoencephalography. Lumbar CSF cAMP concentration was significantly increased in patients in hepatic coma. The concentration of cAMP in the lateral ventricle was not affected by general anaesthesia or by the presence of a complete block of the aqueduct of Sylvius. There was no decrease in lumbar CSF cAMP in patients with a complete stenosis of the aqueduct of Sylvius, partial blocks of CSF flow at the cervical level, or a complete block at the lower thoracic level. The concentration of cisternal CSF cAMP was similar to that of lumbar CSF. These results suggest that (1) there is a ventriculolumbar gradient in the concentration of cAMP but of insufficient magnitude to be detected by mixing of lumbar and ventricular CSF during pneumoencephalography, (2) lumbar CSF cAMP concentration is not dependent on brain as a source of this nucleotide; the source of this nucleotide may be largely derived from the spinal cord, (3) premedication may affect the concentration of cAMP in lumbar CSF cAMP, (4) the formation of cAMP is unimpaired in hepatic coma.