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

Abstract

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. Veratridine (50 microM) or depolarization by 40 mM KCl elicits a significant release of endogenous D-serine from primary neuronal cultures. Controls with astrocyte cultures indicate that glial cells are insensitive to veratridine, but release D-serine mainly by the opening of volume-regulated anion channels. In cortical slices perfused with veratridine, endogenous D-serine release is 10-fold higher than glutamate receptor-evoked release. Release of D-serine from slices does not require internal or external Ca(2+), suggesting a nonvesicular release mechanism. To confirm the neuronal origin of D-serine, we selectively loaded neurons in cortical slices with D-[(3)H]serine or applied D-alanine, which specifically releases D-serine from neurons. Depolarization with veratridine promotes D-serine release in vivo monitored by high temporal resolution microdialysis of the striatum. Our data indicate that the neuronal pool of D-serine plays a major role in D-serine dynamics, with implications for the regulation of NMDAR transmission.

Neuronal d-Serine and Glycine Release Via the Asc-1 Transporter Regulates NMDA Receptor-Dependent Synaptic Activity

“…Subsequently, the slices were equilibrated by a 30 min perfusion with oxygenated MKB in 0.3 ml chambers at a flow rate of 0.6 ml/min in a Suprafusion 1000 (SF-6) apparatus (Brandel) at 37°C. After equilibration in perfusion medium, samples were collected at 1.6 min intervals, and the endogenous D-serine peak was monitored by HPLC as described previously (Rosenberg et al, 2010). To estimate the total D-serine content, the slices were incubated for 20 min with 0.2 M HCl to release all intracellular endogenous D-serine.…”

“…Endogenous glutamate release was monitored by HPLC using the same methodology described above for D-serine. (Rosenberg et al, 2010).…”

“…Hippocampal slices were loaded with 2 M [ 3 H]glycine essentially as described above for D-serine. To ensure that the released radioactivity correspond to authentic glycine, the amino acids were separated by HPLC (Rosenberg et al, 2010), and the peak corresponding to glycine was manually collected and monitored by scintillation counting.…”

FBXO22 Protein Is Required for Optimal Synthesis of the N-Methyl-d-Aspartate (NMDA) Receptor Coagonist d-Serine

“…Serum-free neuronal cultures from the cerebral cortex were prepared from E16 -18 as described previously (24,38) with the following modifications. The culture medium consisted of Neurobasal supplemented with B-27, 0.4 mM glutamine, and penicillin/streptomycin (Neurobasal ϩ B-27).…”

“…Primary astrocytic cultures were carried out with P0-P1 Sprague-Dawley rat pups as described previously (24). The cells were maintained in basal medium Eagle supplemented with 10% FBS, 0.4 mM glutamine, and penicillin/streptomycin and used at DIV14.…”