Mass spectrometric determination of prostanoids in rat hypothalamic paraventricular nucleus microdialysates

The hypothalamic paraventricular nucleus (PVN) is one of the most important autonomic control centers in the brain. Several kinds of prostanoids, such as prostaglandin (PG) E2, are considered to act in the PVN as mediators of autonomic responses. In the present study, we used liquid chromatography ion trap tandem mass spectrometry (LC–ITMSn) to simultaneously quantify four prostanoids, thromboxane (Tx) B2, PGE2, PGD2 and 15-deoxy-∆12,14 (15d)-PGJ2 in PVN microdialysates from urethane-anesthetized rats. The quantification limits were estimated to be 0.05 ng/mL for TxB2, 0.025 ng/mL for PGE2, 0.1 ng/mL for PGD2, and 0.5 ng/mL for 15d-PGJ2. The RSD% obtained from all prostanoids was < 15%, indicating an acceptable level of reproducibility. LC–ITMSn analysis of rat PVN microdialysates revealed that TxA2 may play an important role in adrenomedullary outflow evoked by centrally administered N-methyl-d-aspartate, corticotrophin-releasing factor and glucagon-like peptide-1. This is the first study to use LC–ITMSn to analyze prostanoid levels in rat PVN microdialysates. This LC–ITMSn method will be useful for investigating the potential involvement of prostanoids in brain function.