Cholecystokinin peptides in cerebrospinal fluid: a study in healthy male subjects lumbar-punctured without preceding strict bed-rest.

In a recent study we analysed the concentrations of two forms of cholecystokinin (CCK), CCK-8S (sulphated) and CCK-4 in cerebrospinal fluid (CSF) obtained from 14 healthy male volunteers lumbar-punctured after a minimum of eight hours of strict bed-rest. We have now lumbar-punctured another group of 14 healthy males, using the same procedure except for the requirement of strict bed-rest prior to puncture. In contrast to our previous study, the concentration of CCK-4 (but not CCK-8S) was significantly higher in the second CSF fraction (7-12 ml) than in the first one (0-6 ml). On using the concentration ratio between the second and first fraction, CCK-8S (but not CCK-4) correlated positively with the atmospheric pressure, which is in contrast to our previous study in which a significant negative correlation was found. When the lumbar CSF concentrations were expressed as the concentration per minute of tapping-time (an estimate of the mass flow), atmospheric pressure, age and the neuraxis distance in the lying position made significant contributions to the variance in CCK-8S. A significant positive correlation with atmospheric pressure was found for CCK-4. In conclusion, the results indicate that the question of strict bed-rest or not prior to lumbar puncture may have to be considered when interpreting data on lumbar CSF concentrations of CCK. A controlled study is warranted.