While studying the physiological response of primary rat astrocytes to fluid shear stress in a model of traumatic brain injury (TBI), we found that shear stress induced Ca2+ entry. The influx was inhibited by MK-801, a specific pore blocker of N-Methyl-D-aspartic acid receptor (NMDAR) channels, and this occurred in the absence of agonists. Other NMDA open channel blockers ketamine and memantine showed a similar effect. The competitive glutamate antagonists AP5 and GluN2B-selective inhibitor ifenprodil reduced NMDA-activated currents, but had no effect on the mechanically induced Ca2+ influx. Extracellular Mg2+ at 2 mM did not significantly affect the shear induced Ca2+ influx, but at 10 mM it produced significant inhibition. Patch clamp experiments showed mechanical activation of NMDAR and inhibition by MK-801. The mechanical sensitivity of NMDARs may play a role in the normal physiology of fluid flow in the glymphatic system and it has obvious relevance to TBI.

Background: The C-terminal domains (CTDs) of NMDA receptors are essential for normal brain function. Results: We developed kinetic mechanisms for receptors lacking CTDs using single-channel methods. Conclusion: GluN1 CTDs control primarily unitary conductance and GluN2 CTDs control gating kinetics. Significance: Results afford quantitative insight into how intracellular perturbations can change the time course of NMDA receptor currents.

Background: PKA increases NMDA receptor responses and phosphorylates multiple residues on C-terminal domains (CTD). Results: PKA inhibition reduced gating through GluN2B CTD and reduced Ca 2ϩ permeability through GluN1 CTD. Conclusion: PKA controls NMDA receptor gating and Ca 2ϩ permeability through distinct sites. Significance: Dissecting the complex modulatory effects of PKA on NMDA receptors helps delineate fundamental mechanisms of synaptic regulation.

PURPOSEThe implementation of electronic health records (EHRs) has been extensively studied, but their maintenance once implemented has not. The Regional Extension Center (REC) program provides implementation assistance to priority practices-those with limited financial, technical, and organizational resources-but the assistance is time limited. Our objective was to identify potential barriers to maintenance of meaningful use of EHRs in priority primary care practices using a qualitative observational study for federally qualified health centers (FQHCs) and priority practices in Michigan. METHODSWe conducted cognitive task analysis (CTA) interviews and direct observations of health information technology implementation in FQHCs. In addition, we conducted semistructured interviews with implementation specialists serving priority practices to detect emergent themes relevant to maintenance. RESULTSMaintaining EHR technology will require ongoing expert technical support indefinitely beyond implementation to address upgrades and security needs. Maintaining meaningful use for quality improvement will require ongoing support for leadership and change management. Priority practices not associated with larger systems lack access to the necessary technical expertise, financial resources, and leverage with vendors to continue alone. Rural priority practices are particularly challenged, because expertise is often not available locally.CONCLUSIONS Priority practices, especially in rural areas, are at high risk for falling on the wrong side of a "digital divide" as payers and regulators enact increasing expectations for EHR use and information management. For those without affiliation to maintain the necessary expert staff, ongoing support will be needed for those practices to remain viable.

Ion channel proteins are universal devices for fast communication across biological membranes. The temporal signature of the ionic flux they generate depends on properties intrinsic to each channel protein as well as the mechanism by which it is generated and controlled and represents an important area of current research. Information about the operational dynamics of ion channel proteins can be obtained by observing long stretches of current produced by a single molecule. Described here is a protocol for obtaining one-channel cell-attached patchclamp current recordings for a ligand gated ion channel, the NMDA receptor, expressed heterologously in HEK293 cells or natively in cortical neurons. Also provided are instructions on how to adapt the method to other ion channels of interest by presenting the example of the mechanosensitive channel PIEZO1. This method can provide data regarding the channel's conductance properties and the temporal sequence of openclosed conformations that make up the channel's activation mechanism, thus helping to understand their functions in health and disease. Video LinkThe video component of this article can be found at

NMDA receptor conductance and gating is directly affected by fluctuations in extracellular calcium concentration.

NMDA receptors are glutamate-activated, Ca ( 2+) -permeable ion channels with critical roles in synaptic transmission and plasticity. The shape and size of their current is modulated by several kinase/phosphatase systems, and numerous residues located on the receptors' intracellular C-termini are phosphorylated in vivo. To investigate the mechanisms by which phosphorylation may control channel gating, we examined the single-channel behaviors of receptors carrying the S900A or S929A substitution in their GluN2A subunits and thus were rendered resistant to phosphorylation at those sites. We found that the mutations reduced channel open probability primarily by increasing the frequency of desensitized events. The kinetic models we developed revealed complex but similar changes in mechanism for the two mutants, leading to the view that dephosphorylation at either site may cause receptors to activate slower, deactivate faster and desensitize more frequently. This modulatory mechanism is consistent with the proposed roles for these residues in Ca ( 2+) -dependent desensitization and calcineurin-mediated reduction of current during brain development.

Membrane stretch gates NMDA receptor currents in the absence of neurotransmitter. Stretchgated currents have the biophysical hallmarks of the glutamate-gated currents including requirement for glycine, large Na + conductance, high Ca 2+ permeability, and voltage-dependent Mg 2+ block..