Altered mnemonic functions and resistance to N-METHYL-d-Aspartate receptor antagonism by forebrain conditional knockout of glycine transporter 1.

Converging evidence from pharmacological and molecular studies has led to the suggestion that inhibition of glycine transporter 1 (GlyT1) constitutes an effective means to boost N-methyl-d-aspartate receptor (NMDAR) activity by increasing the extra-cellular concentration of glycine in the vicinity of glutamatergic synapses. However, the precise extent and limitation of this approach to alter cognitive function, and therefore its potential as a treatment strategy against psychiatric conditions marked by cognitive impairments, remain to be fully examined. Here, we generated mutant mice lacking GlyT1 in the entire forebrain including neurons and glia. This conditional knockout system allows a more precise examination of GlyT1 downregulation in the brain on behavior and cognition. The mutation was highly effective in attenuating the motor-stimulating effect of acute NMDAR blockade by phencyclidine, although no appreciable elevation in NMDAR-mediated excitatory postsynaptic currents (EPSC) was observed in the hippocampus. Enhanced cognitive performance was observed in spatial working memory and object recognition memory while spatial reference memory and associative learning remained unaltered. These findings provide further credence for the potential cognitive enhancing effects of brain GlyT1 inhibition. At the same time, they indicated potential phenotypic differences when compared with other constitutive and conditional GlyT1 knockout lines, and highlighted the possibility of a functional divergence between the neuronal and glia subpopulations of GlyT1 in the regulation of learning and memory processes. The relevance of this distinction to the design of future GlyT1 blockers as therapeutic tools in the treatment of cognitive disorders remains to be further investigated.

Development of a gas chromatography-mass spectrometry method for determination of ketamine in plasma and its application to human samples.

A sensitive and precise gas chromatography-mass spectrometry method with selected ion monitoring has been developed for identification and quantification of the phencyclidine derivative ketamine in human plasma. The assay is based on an alkaline extraction from aqueous to organic solvent from plasma and an efficient gas chromatographic separation on a DB-5 capillary column. The analytical procedure has a coefficient of variation of 0.7-6.2% and from 1.3 to 8.7% within-day and from day-to-day analysis, respectively. The low level of sensitivity was 10 ng/ml. It was used to measure low plasma concentrations in volunteers during ketamine-induced experimental psychosis. The method is not enantio selective.

Identification and quantification of ergotamine in human plasma by gas chromatography-mass spectrometry.

A highly sensitive and simple gas chromatographic-mass spectrometric method is described for the identification and quantification of ergotamine in plasma or serum. Ergotamine is extracted with chloroform from the alkalinized sample and detected by electron ionization mass spectrometry. This analytical method was selected for an intense high-mass ion ideal for the specific quantification. It shows good linearity in the range from 50 pg/ml to 50 ng/ml for ergotamine in plasma. The practicability of this method is demonstrated by determining the plasma concentration of ergotamine in a sample from a patient.