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The nerve terminals found in the body wall of Drosophila melanogaster larvae are readily accessible to experimental manipulation. We used the light-activated ion channel, channelrhodopsin-2, which is expressed by genetic manipulation in Type II varicosities to study octopamine release in Drosophila. We report the development of a method to measure neurotransmitter release from exocytosis events at individual varicosities in the Drosophila larval system by amperometry. A microelectrode was placed in a region of the muscle containing a varicosity and held at a potential sufficient to oxidize octopamine and the terminal stimulated by blue light. Optical stimulation of Type II boutons evokes exocytosis of octopamine, which is detected through oxidization at the electrode surface. We observe 22700±4200 molecules of octopamine released per vesicle. This system provides a genetically accessible platform to study the regulation of amine release at an intact synapse.

In this article, the numerical approach for flow profile reconstruction in a microfluidic channel equipped with band microelectrodes introduced previously by the authors, based on transient currents, is extended to the exclusive use of steady-state currents. It is shown that, although the currents obey steady state, the flow velocity profile in the channel may be reconstructed rapidly with a high accuracy, provided a sufficient number of electrodes performing under steady state are considered. The present theory demonstrates how the electrode widths and sizes of gaps separating them can be optimized to achieve better performance of the method. This approach has been evaluated theoretically for band microelectrode arrays embedded into one wall of a rectangular channel consisting of three, four, or five electrodes, all of which are operated in the generator mode. The results prove that the proposed approach is able to accurately recover the shape of the flow profile in a wide range of Peclet numbers and flow types ranging from the classical parabolic Poiseuille flow to constant electro-osmotic-type flow.

Chemical synaptic transmission is central to the brain functions. In this regard, real-time monitoring of chemical synaptic transmission during neuronal communication remains a great challenge. In this work, in vivo-like oriented neural networks between superior cervical ganglion (SCG) neurons and their effector smooth muscle cells (SMC) were assembled in a microfluidic device. This allowed amperometric detection of individual neurotransmitter release events inside functional SCG-SMC synapse with carbon fiber nanoelectrodes as well as recording of postsynaptic potential using glass nanopipette electrodes. The high vesicular release activities essentially involved complex events arising from flickering fusion pores as quantitatively established based on simulations. This work allowed for the first time monitoring in situ chemical synaptic transmission under conditions close to those found in vivo, which may yield important and new insights into the nature of neuronal communications. [ABSTRACT FROM AUTHOR]

The nerve terminals found in the body wall of Drosophila melanogaster larvae are readily accessible to experimental manipulation. We used the light-activated ion channel, channelrhodopsin-2, which is expressed by genetic manipulation in Type II varicosities to study octopamine release in Drosophila. We report the development of a method to measure neurotransmitter release from exocytosis events at individual varicosities in the Drosophila larval system by amperometry. A microelectrode was placed in a region of the muscle containing a varicosity and held at a potential sufficient to oxidize octopamine and the terminal stimulated by blue light. Optical stimulation of Type II boutons evokes exocytosis of octopamine, which is detected through oxidization at the electrode surface. We observe 22700±4200 molecules of octopamine released per vesicle. This system provides a genetically accessible platform to study the regulation of amine release at an intact synapse., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Chemical synaptic transmission is central to the brain functions. In this regard, real-time monitoring of chemical synaptic transmission during neuronal communication remains a great challenge. In this work, in vivo-like oriented neural networks between superior cervical ganglion (SCG) neurons and their effector smooth muscle cells (SMC) were assembled in a microfluidic device. This allowed amperometric detection of individual neurotransmitter release events inside functional SCG-SMC synapse with carbon fiber nanoelectrodes as well as recording of postsynaptic potential using glass nanopipette electrodes. The high vesicular release activities essentially involved complex events arising from flickering fusion pores as quantitatively established based on simulations. This work allowed for the first time monitoring in situ chemical synaptic transmission under conditions close to those found in vivo, which may yield important and new insights into the nature of neuronal communications., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)