Formation of D-serine from L-phosphoserine in brain synaptosomes.

Although glycine has been assumed to be the sole endogenous coagonist at NMDA-associated glycine receptors, recent descriptions of endogenous D-serine in the brain indicate that this assumption is probably not valid. D-Serine is a stereospecific agonist of the NMDA-associated glycine receptor, with an affinity equal to or greater than that of glycine but with no affinity for the strychnine-sensitive glycine receptor. In the current studies, we assessed the levels and metabolic sources of D-serine in rat neocortical synaptosomal preparations.

Steroid inhibition of [3H]SR 95531 binding to the GABAA recognition site.

The interaction of three types of steroids with the GABAA recognition site labeled by the antagonist ligand [3H]SR 95531 was evaluated in rat brain cortical membranes. The first type is the GABA site antagonist RU 5135, which potently (IC50 7 nM) but also incompletely (Imax 82%) displaced [3H]SR 95531. RU 5135 probably binds only to high affinity [3H]SR 9553] sites recognized by GABA and unlabelled SR 95531.

Simultaneous quantification of fluoxetine, norfluoxetine, and desipramine using gas chromatography with nitrogen-phosphorus detection.

The combination of fluoxetine (FLU) and desipramine (DMI) has been reported to be useful for the treatment of depression, and these drugs are also known to undergo a metabolic drug-drug interaction because of their effects on cytochrome P-450 2D6. A procedure that separates these two drugs and norfluoxetine (NFLU), the N-demethylated metabolite of FLU, and that allows simultaneous quantification of their levels would be of value and has been developed in our laboratories. The procedure involves an initial extraction into ethyl acetate after basification of the homogenate.

Separation and quantification of D- and L-phosphoserine in rat brain using N alpha-(2,4-dinitro-5-fluorophenyl)-L-alaninamide (Marfey's reagent) by high-performance liquid chromatography with ultraviolet detection.

D-Serine has recently been described to be present in the brain at high concentrations. However, while prior research has demonstrated that L-phosphoserine is the major precursor of L-serine in the brain, the possible role of D-phosphoserine as the direct precursor of D-serine is unknown. To address this problem, we developed an assay to separate and quantitate D- and L-phosphoserine.

Rapid and sensitive procedure for the separation and quantitation of D- and L-serine in rat brain using gas chromatography-mass spectrometry.

A very simple and rapid GC-MS procedure for the separation and quantitation of D- and L-serine has been developed utilizing a conventional bonded-phase capillary column. The procedure involves initial esterification with isobutanol followed by acylation with the chiral derivatizing reagent S-(-)-N-(heptafluorobutyryl)prolyl chloride (HPC). This procedure requires neither extraction nor clean-up steps and is sensitive to 50 pg on-column.