ATP derived from astrocytes modulates memory in the chick.

Memory consolidation in a discriminative bead pecking task is modulated by endogenous adenosine triphosphate (ATP) acting at purinergic receptors in the hippocampus. Consolidation, from short- to intermediate- to long-term memory during two distinct periods following training, was blocked by the non-selective P2 purinergic receptor antagonist PPADS (pyridoxal phosphate-6-azo(benzene-2,4-disulphonic acid) tetrasodium salt hydrate and the specific P2Y1 receptor antagonist MRS2179. Direct injections of the ATP agonists (ATPγS and ADPβS) potentiated memory consolidation and the effect of ADPβS was blocked by MRS2179, suggesting an important role of ATP on memory consolidation via the P2Y1 receptor in the chick hippocampus.

Neuronal release of D-serine: a physiological pathway controlling extracellular D-serine concentration.

D-serine is thought to be a glia-derived transmitter that activates N-methyl D-aspartate receptors (NMDARs) in the brain. Here, we investigate the pathways for D-serine release using primary cultures, brain slices, and in vivo microdialysis. In contrast with the notion that D-serine is exclusively released from astrocytes, we found that D-serine is released by neuronal depolarization both in vitro and in vivo.

Neuron-derived D-serine release provides a novel means to activate N-methyl-D-aspartate receptors.

D-serine is a coagonist of N-methyl-D-aspartate (NMDA) receptors that occurs at high levels in the brain. Biosynthesis of D-serine is carried out by serine racemase, which converts L- to D-serine. D-serine has been demonstrated to occur in glial cells, leading to the proposal that astrocytes are the only source of D-serine.

D-serine is the dominant endogenous coagonist for NMDA receptor neurotoxicity in organotypic hippocampal slices.

D-serine occurs at high levels in the brain, where it is an endogenous coagonist at the "glycine site" of NMDA receptors. However, D-serine action has not been previously compared with that of endogenous glycine, and the relative importance of the two coagonists remains unclear. We now investigated the efficiencies of the two coagonists in mediating NMDA receptor neurotoxicity in organotypic hippocampal slices.

Serine racemase modulates intracellular D-serine levels through an alpha,beta-elimination activity.

Mammalian brain contains high levels of d-serine, an endogenous co-agonist of N-methyl D-aspartate type of glutamate receptors. D-Serine is synthesized by serine racemase, a brain enriched enzyme converting L- to D-serine. Degradation of D-serine is achieved by D-amino acid oxidase, but this enzyme is not present in forebrain areas that are highly enriched in D-serine.

Liver sinusoidal endothelial cell modulation upon resection and shear stress in vitro.

BACKGROUND: Shear stress forces acting on liver sinusoidal endothelial cells following resection have been noted as a possible trigger in the early stages of hepatic regeneration. Thus, the morphology and gene expression of endothelial cells following partial hepatectomy or shear stress in vitro was studied. RESULTS: Following partial hepatectomy blood flow-to-liver mass ratio reached maximal values 24 hrs post resection.