INCREASED CEREBROSPINAL-FLUID CONCENTRATION OF ASPARTATE BUT DECREASED CONCENTRATION OF NITRIC-OXIDE BREAKDOWN PRODUCTS IN WOMEN EXPERIENCING VISCERAL PAIN DURING ACTIVE LABOR

THE aim of the present study was to investigate some putative neurotra nsmitters involved in nociception and pain in parturients during activ e labour experiencing intense visceral pain. The concentration of the excitatory amino acid aspartate was significantly increased, and there was a tendency for an increase in glutamate, in lumbar cerebrospinal fluid (CSF) of parturients in active vaginal labour compared with cont rol patients without pain subjected to elective caesarean section. The CSF concentration of the nitric oxide breakdown product nitrate was s ignificantly decreased in parturients compared with control patients a nd healthy volunteers. No significant differences in the concentration s of substance P, substance P-endopeptidase or met-enkephalin were det ected between parturients and controls. Our data suggest a paradoxical negative relationship between CSF concentrations of excitatory amino acids and nitric oxide in labour pain. The mechanisms behind this find ing is unclear at present.