The structure and connectivity of cultured neuronal networks can be controlled by using micropatterned surfaces. Here, we demonstrate that the direction of signal propagation can be precisely controlled at a single-cell resolution by growing primary neurons on micropatterns. To achieve this, we first examined the process by which axons develop and how synapses form in micropatterned primary neurons using immunocytochemistry. By aligning asymmetric micropatterns with a marginal gap, it was possible to pattern primary neurons with a directed polarization axis at the single-cell level. We then examined how synapses develop on micropatterned hippocampal neurons. Three types of micropatterns with different numbers of short paths for dendrite growth were compared. A normal development in synapse density was observed when micropatterns with three or more short paths were used. Finally, we performed double patch clamp recordings on micropatterned neurons to confirm that these synapses are indeed functional, and that the neuronal signal is transmitted unidirectionally in the intended orientation. This work provides a practical guideline for patterning single neurons to design functional neuronal networks with the direction of signal propagation being controlled.

Antiplatelet therapy is the mainstay of pharmacologic treatment to prevent thrombotic or ischemic events in patients with coronary artery disease treated with percutaneous coronary intervention and those treated medically for an acute coronary syndrome. The use of antiplatelet therapy comes at the expense of an increased risk of bleeding complications. Defining the optimal intensity of platelet inhibition according to the clinical presentation of atherosclerotic cardiovascular disease and individual patient factors is a clinical challenge. Modulation of antiplatelet therapy is a medical action that is frequently performed to balance the risk of thrombotic or ischemic events and the risk of bleeding. This aim may be achieved by reducing (ie, de-escalation) or increasing (ie, escalation) the intensity of platelet inhibition by changing the type, dose, or number of antiplatelet drugs. Because de-escalation or escalation can be achieved in different ways, with a number of emerging approaches, confusion arises with terminologies that are often used interchangeably. To address this issue, this Academic Research Consortium collaboration provides an overview and definitions of different strategies of antiplatelet therapy modulation for patients with coronary artery disease, including but not limited to those undergoing percutaneous coronary intervention, and consensus statements on standardized definitions.

Electrical signals of neuronal cells can be recorded non-invasively and with a high degree of temporal resolution using multielectrode arrays (MEAs). However, signals that are recorded with these devices are small, usually 0.01%-0.1% of intracellular recordings. Here, we show that the amplitude of neuronal signals recorded with MEA devices can be amplified by covering neuronal networks with an electrically resistive sheet. The resistive sheet used in this study is a monolayer of glial cells, supportive cells in the brain. The glial cells were grown on a collagen-gel film that is permeable to oxygen and other nutrients. The impedance of the glial sheet was measured by electrochemical impedance spectroscopy, and equivalent circuit simulations were performed to theoretically investigate the effect of covering the neurons with such a resistive sheet. Finally, the effect of the resistive glial sheet was confirmed experimentally, showing a 6-fold increase in neuronal signals. This technique feasibly amplifies signals of MEA recordings. V C 2016 AIP Publishing LLC. Microelectrode array (MEA) technology is widely used to record trains of action potentials from cultured neurons, cardiomyocytes, or brain slice preparations. [1][2][3][4] The major advantage of this method lies in its high temporal resolution (>10 kHz) and non-invasiveness. MEA recordings have been used both in fundamental studies, e.g., to analyse activity patterns of cultured neuronal networks, 5,6 and in pharmacological research, for screening lead compounds in vitro. 7,8 However, small signals that can be detected through extracellularly positioned microelectrodes inhibit MEAs from being used in further applications such as studies of subthreshold activity. The amplitude of extracellularly recorded signals is usually in the order of ten to a hundred microvolts, which is 3-4 orders of magnitude lower than the intracellular change of membrane potential in an action potential ($100 mV).Various attempts have been made to overcome this issue. One approach involves increasing the seal resistance between the cell and the electrode. This can be achieved by using nanostructured electrodes instead of planar electrodes that become engulfed by overlying cells. 1,9 A second approach is to decrease the electrode impedance. To record activity from single cells, the use of a smaller electrode is preferable, but this comes at the cost of increased electrode impedance, which decreases the signal. Wolfrum et al. overcame this dilemma by creating micropores that interface the cells to larger electrodes. 10,11 A third approach involves decreasing the membrane impedance at the cell-electrode junction. In practice, this involves transiently rapturing the cell membrane by applying a zap voltage to a nanostructured electrode, thus allowing the electrodes to enter the cell and perform pseudo-intracellular recording until the raptured membrane reorganizes. 1,12,13 In this letter, we propose an alternative approach to increase the neuron-electrode seal for amplifying signals in ex...

The electrical impedance of cell membranes is important for excitable cells, such as neurons, because it strongly influences the amount of membrane potential change upon a flow of ionic current across the membrane. Here, we report on an investigation of how neuronal morphology affects membrane impedance of cultured hippocampal neurons. Microfabricated substrates with patterned scaffolding molecules were used to restrict the neurite growth of hippocampal neurons, and the impedance was measured via whole-cell patch-clamp recording under the inhibition of voltage-dependent ion channels. Membrane impedance was found to depend inversely on the dendrite length and soma area, as would be expected from the fact that its electrical property is equivalent to a parallel RC circuit. Moreover, we found that in biological neurons, the membrane impedance is homeostatically regulated to impede changes in the membrane area. The findings provide direct evidence on cell-autonomous regulation of neuronal impedance and pave the way towards elucidating the mechanism responsible for the resilience of biological neuronal networks.

No abstract