PHYSIOLOGICAL-CHARACTERISTICS OF SOME MONOAMINE METABOLITES IN CAT CEREBROSPINAL-FLUID

The concentrations of main metabolites of serotonin and dopamine, 5-hy droxyindoleacetic acid and homovanillic acid, respectively, were measu red in cisternal cerebrospinal fluid of cats by high performance liqui d chromatography with an electrochemical detector. Higher concentratio ns of homovanillic acid and a wide interindividual oscillation for bot h parameters have been found. However, samples collected at four diffe rent time intervals showed stabile intraindividual concentrations of t he metabolites. The existence of a concentration gradient of both para meters inside the cat cerebrospinal fluid system was confirmed in expe riments with a provoked artificial flow of cerebrospinal fluid inside physiological limits. These experiments also suggested that the hydrod ynamics of cerebrospinal fluid is the factor responsible for the conce ntration gradient existence. It appears that the absence of cerebrospi nal fluid circulation is the main hydrodynamic reason for the maintena nce of 5-hydroxyindoleacetic acid and homovanillic acid gradients betw een various parts of the cerebrospinal fluid system.