Do concentrations of neurotransmitters measured in lumbar cerebrospinal fluid reflect the concentrations at brain level?

CSF concentrations of vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), noradrenaline (NA) and dopamine (DA) were measured in the lateral ventricles and at the lumbar level in patients with normal pressure hydrocephalus (NPH). The concentrations of VIP (n = 15), NA (n = 10) and DA (n = 10) were significantly higher at the lumbar level than at the ventricular level, whereas the concentrations of CCK (n = 9) were similar at the two sites. A significant positive correlation between the concentrations measured at the two levels was found for VIP (rs = 0.65; p less than or equal to 0.01) and DA (rs = 0.94; p less than or equal to 0.001). The results indicate that the concentrations of transmitter substances measured in CSF at the lumbar level not necessarily are indicative for concentrations measured more centrally. The negative correlations between Evans ratio and L-CSF VIP (rs = -0.76; p less than or equal to 0.001), and between resistance to outflow and V-CSF as well as L-CSF CCK (rs = -0.75); p less than or equal to 0.05) might be explained by a reduction in number of cortical neurons or by disturbances in CSF dynamics in patients with NPH.