Single Synaptic Observation of Cholinergic Neurotransmission on Living Neurons: Concentration and Dynamics

Abstract

Acetylcholine, the first neurotransmitter identified more than a century ago, plays critical roles in human activities and health; however, its synaptic concentration dynamics have remained unknown. Here, we demonstrate the in situ simultaneous measurements of synaptic cholinergic transmitter concentration and release dynamics. We used nanoscale electroanalytical methods: nanoITIES electrode of 15 nm in radius and nanoresolved scanning electrochemical microscopy (SECM). Time-resolved in situ measurements unveiled information on synaptic acetylcholine concentration and release dynamics of living Aplysia neurons. The measuring technique enabled the quantitative sensing of acetylcholine with negligible interference of other ionic and redox-active species. We measured cholinergic transmitter concentrations very close to the synapse, with values as high as 2.4 mM. We observed diverse synaptic transmitter concentration dynamics consisting of singlet, doublet and multiplet events with a signal-to-noise ratio of 6 to 130. The unprecedented details about synaptic neurotransmission unveiled are instrumental for understanding brain communication and diseases in a way distinctive from extra-synaptic studies.

A Newly Synthesized Tris(crown ether) Ionophore for Assisted Ion Transfer at NanoITIES Electrodes

“…0.7 mm, length=7.5 cm) using a P‐2000 capillary puller (Sutter Instrument Co., Novato, CA). The nanopipets were fabricated using procedures as previously reported …”

“…An Ag wire (diameter=250 μm) coated with AgCl (through an oxidation reaction in saturated KCl solution) was placed in the aqueous phase as an outside reference electrode. A two electrode configuration was used as reported previously, where a potential was applied between the inner Pt wire and the outer Ag/AgCl reference electrode . Positive potential is for positive ion transfer from water to oil (1, 2‐DCE), seen as positive current.…”

Fast serotonin voltammetry as a versatile tool for mapping dynamic tissue architecture: I. Responses at carbon fibers describe local tissue physiology

“…As such, subtle alterations in the function of these modulators are thought to underlie the phenotypes of many disorders of the brain (Owens and Nemeroff ; Abi‐Dargham et al ; Volkow and Fowler ; Oades ; Muller et al ). To better understand the functional importance of messengers like serotonin in the brain, analytical measurements of neurotransmitters is a thriving and rapidly evolving field (Meunier et al ; Johnson et al ; Shen et al ). To this end, we have thus far focused on pioneering in vivo measurements of evoked and ambient serotonin using fast‐scan cyclic voltammetry (FSCV) and fast‐scan controlled adsorption voltammetry (FSCAV) at carbon fiber microelectrodes (CFMs) (Hashemi et al ; Abdalla et al ).…”

Harpagide, a natural product, promotes synaptic vesicle release as measured by nanoelectrode amperometry

“…[37][38][39][40][41][42][43][44][45][46][47][48] Further combining with scanning electrochemical microscopy (SECM) or scanning ion conductance microscopy (SICM) allows electrochemical and topographical imaging of neurons and detection of neurotransmitter release with super resolution. [49][50][51] Recently, amperometry at carbon-based nanoelectrodes has demonstrated its unique advantages for monitoring in real time individual vesicular exocytotic events from single synapses or varicosities and providing statistically signicant quantitative and kinetic information achievable by no other methods. 52,53 In this work, extremely tiny carbon ber nanoelectrodes with smaller size and higher spatial resolution that our previous ones were fabricated (Fig.…”