An analysis of excitatory amino acids, nitric oxide, and prostaglandin E2 in the cerebrospinal fluid of pregnant women: the effect on labor pain.

It is still unclear which neurotransmitters are involved in labor pain. We measured the concentrations of excitatory amino acids, nitric oxide, and prostaglandin E 2 in the cerebrospinal fluid (CSF) of pregnant women, particularly in those with labor pain. The patients included in the study consisted of women who underwent cesarean delivery either with labor pain (Labor Pain group, n = 40) or without labor pain (Nonlabor Pain group, n = 58). All patients received spinal anesthesia (intrathecal injection of 10-12 mg of bupivacaine) for the operation, and 2 mL of CSF was collected before bupivacaine injection. Concentrations of aspartate and glutamate (0.50 ± 0.06 μM and 0.79 ± 0.10 μM, respectively) were significantly larger in the Labor Pain group than in the Nonlabor Pain group (0.35 ± 0.03 μM and 0.54 ± 0.04 μM, P < 0.05). There were no significant differences in the concentrations of nitric oxide and prostaglandin E 2 between the groups. A positive correlation was found between CSF concentrations of excitatory amino acids and labor pain.