Dual-Channel Electrochemical Measurements Reveal Rapid Adenosine is Localized in Brain Slices

Flexible needle-type Microbiosensor for real-time monitoring traditional acupuncture-mediated adenosine release In vivo

Rapid adenosine (ADO) signaling, on the time frame of seconds, regulates physiological and pathological processes, including the therapeutic efficacy of acupuncture. Nevertheless, standard monitoring strategies are limited by poor temporal resolution. Herein, an implantable needle-type microsensor capable of monitoring ADO release in vivo in response to acupuncture in real time has been developed. Electrocatalytic Prussian Blue nanoparticles, an immobilized multienzyme system, and a permselective poly-o-phenylenediamine-based membrane were used for the sequential modification of the sensing region of the electrode. The resultant sensor can perform amperometric measurements of ADO levels in response to a very low level of applied potential (-0.05 V vs Ag/AgCl). This microsensor also functioned across a broad linear range (0-50 μM) and exhibited good sensitivity (1.1 nA/μM) with a rapid response time of under 5 s. Importantly, the sensor also exhibited good reproducibility and high selectivity. For in vivo animal studies, the microsensor was employed for the continuous assessment of instantaneous ADO release at the ST36 (Zusanli) acupoint when this acupoint was subjected to twirling-rotating acupuncture manipulation. Benefiting from superior sensor in vivo performance and stability, the positive correlation between the variability in acupuncture-induced ADO release and the stimulus intensity levels that affect the clinical benefit can be demonstrated for the first time. Overall, these results highlight a powerful approach to analyzing the in vivo physiological effects of acupuncture, expanding application realm of micro-nano sensor technology on a fast time scale.

Astroglial CB1 receptors, energy metabolism, and gliotransmission: an integrated signaling system?

Astrocytes are key players in brain homeostasis and function. During the last years, several studies have cemented this notion by showing that these cells respond to neuronal signals and, via the release of molecules that modulate and support synaptic activity (gliotransmission) participates in the functions of the so-called tripartite synapse. Thus, besides their established control of brain metabolism, astrocytes can also actively control synaptic activity and behavior. Among the signaling pathways that shape the functions of astrocyte, the cannabinoid type-1 (CB1) receptor is emerging as a critical player in the control of both gliotransmission and the metabolic cooperation between astrocytes and neurons. In the present short review, we describe known and newly discovered properties of the astroglial CB1 receptors and their role in modulating brain function and behavior. Based on this evidence, we finally discuss how the functions and mode of actions of astrocyte CB1 receptors might represent a clear example of the inextricable relationship between energy metabolism and gliotransmission. These tight interactions will need to be taken into account for future research in astrocyte functions and call for a reinforcement of the theoretical and experimental bridges between studies on metabolic and synaptic functions of astrocytes.

Carbon microelectrodes with customized shapes for neurotransmitter detection: A review

Carbon is a popular electrode material for neurotransmitter detection due to its good electrochemical properties, high biocompatibility, and inert chemistry. Traditional carbon electrodes, such as carbon fibers, have smooth surfaces and fixed shapes. However, newer studies customize the shape and nanostructure the surface to enhance electrochemistry for different applications. In this review, we show how changing the structure of carbon electrodes with methods such as chemical vapor deposition (CVD), wet-etching, direct laser writing (DLW), and 3D printing leads to different electrochemical properties. The customized shapes include nanotips, complex 3D structures, porous structures, arrays, and flexible sensors with patterns. Nanostructuring enhances sensitivity and selectivity, depending on the carbon nanomaterial used. Carbon nanoparticle modifications enhance electron transfer kinetics and prevent fouling for neurochemicals that are easily polymerized. Porous electrodes trap analyte momentarily on the scale of an electrochemistry experiment, leading to thin layer electrochemical behavior that enhances secondary peaks from chemical reactions. Similar thin layer cell behavior is observed at cavity carbon nanopipette electrodes. Nanotip electrodes facilitate implantation closer to the synapse with reduced tissue damage. Carbon electrode arrays are used to measure from multiple neurotransmitter release sites simultaneously. Custom-shaped carbon electrodes are enabling new applications in neuroscience, such as distinguishing different catecholamines by secondary peaks, detection of vesicular release in single cells, and multi-region measurements in vivo.