Lumbar puncture in psychiatric research : on the impact of confounding factors on monoamine compounds in cerebrospinal fluid

Sammanfattning: Lumbar puncture has for many years been a tool for investigations of cerebrospinal fluid (CSF) in man. The method has been in use since 1891 and is common in neurology, and other medical specialities. In psychiatry it has been used in research to discover abnormalities, mainly in neurotransmitter turnover and to find correlations to clinical observations concerning i.e. depressions, schizophrenia, suicide, aggressive behaviour. The results from previous research, however, have not always been conclusive and reproduceable. Several confounding factors have been assumed to explain some of the discrepancies. In order to elucidate the role of some of the confounders this study was carried out. Four groups of male volunteers, one group of female volunteers and one group of pathological male gamblers were lumbar punctured in a standardised way with variations for bedrest, posture at puncture and atmospheric pressure (performed in a pressure chamber). The results were analysed by taking a number of previously described confounders (gender, age, weight, height, neuroaxis distance, tapping-time, posture, motor activity, ambient atmospheric pressure and storage time for samples) into consideration. Atmospheric pressure and HMPG correlated in females not using oral contraceptives. Compared to healthy males, tapping-time was longer for female volunteers and pathological male gamblers. An HMPG gradient was found for male volunteers only. Taking tapping-time into consideration, the mass flow of 5-HIAA through the lumbar puncture needle was lower in gamblers than controls, a finding that provides some evidence for altered serotonin function in pathological gambling. The 5-HIAA and HVA concentrations in the CSF were 35% and 62% lower in a group of male volunteers lumbar punctured without preceding strict bedrest compared to male subjects lumbar punctured after bedrest. There is evidence for an influence of CSF pressure on tapping-time and on the CSF distribution of tryptophan and 5-HIAA. It is plausible that atmospheric pressure exerts an effect, especially on the cathecolamine distribution in CSF. Several other correlations between monoamine compounds and confounders were found.