Real-Time Fast Scan Cyclic Voltammetry Detection and Quantification of Exogenously Administered Melatonin in Mice Brain.

Elisa Castagnola,Elaine M Robbins,Adrian C Michael,Kevin M Woeppel,Xinyan Tracy Cui,I Mitch Taylor,Moriah Mcguier,Asiyeh Golabchi

doi:10.3389/fbioe.2020.602216

Abstract

Melatonin (MT) has been recently considered an excellent candidate for the treatment of sleep disorders, neural injuries, and neurological diseases. To better investigate the actions of MT in various brain functions, real-time detection of MT concentrations in specific brain regions is much desired. Previously, we have demonstrated detection of exogenously administered MT in anesthetized mouse brain using square wave voltammetry (SWV). Here, for the first time, we show successful detection of exogenous MT in the brain using fast scan cyclic voltammetry (FSCV) on electrochemically pre-activated carbon fiber microelectrodes (CFEs). In vitro evaluation showed the highest sensitivity (28.1 nA/μM) and lowest detection limit (20.2 ± 4.8 nM) ever reported for MT detection at carbon surface. Additionally, an extensive CFE stability and fouling assessment demonstrated that a prolonged CFE pre-conditioning stabilizes the background, in vitro and in vivo, and provides consistent CFE sensitivity over time even in the presence of a high MT concentration. Finally, the stable in vivo background, with minimized CFE fouling, allows us to achieve a drift-free FSCV detection of exogenous administered MT in mouse brain over a period of 3 min, which is significantly longer than the duration limit (usually < 90 s) for traditional in vivo FSCV acquisition. The MT concentration and dynamics measured by FSCV are in good agreement with SWV, while microdialysis further validated the concentration range. These results demonstrated reliable MT detection using FSCV that has the potential to monitor MT in the brain over long periods of time.

Highlights

Melatonin (MT), the pineal gland’s major secretory product under dark conditions in all mammals, including humans (Farías et al, 2012), is well known for its role in circadian rhythms and modulation of the immune system (Maestroni et al, 1986; Cagnacci et al, 1992; Szczepanik, 2007; Salehi et al, 2019)
We evaluated the sensitivity of our carbon fiber microelectrodes (CFEs) in detecting MT in vitro with a range of MT concentration of 0.1– 5 μM in artificial cerebrospinal fluid (aCSF)
The selectivity of MT detection at CFEs using this fast scan cyclic voltammetry (FSCV) waveform over other electroactive species, including ascorbic acid (AA), dopamine (DA), serotonin (5-HT) and their mixtures, and H2O2 has been evaluated

Summary

Introduction

Melatonin (MT), the pineal gland’s major secretory product under dark conditions in all mammals, including humans (Farías et al, 2012), is well known for its role in circadian rhythms and modulation of the immune system (Maestroni et al, 1986; Cagnacci et al, 1992; Szczepanik, 2007; Salehi et al, 2019). MT’s neuroprotective functions have shown therapeutic potentials for the treatment of amyotrophic lateral sclerosis (Zhang et al, 2013), Huntington’s disease (Túnez et al, 2004; Escribano et al, 2014), and cerebral ischemia (Borlongan et al, 2000; Cuzzocrea et al, 2000), while its anti-inflammatory and anti-nociceptive actions can alleviate chronic pain both in experimental (Mukherjee et al, 2010; Wilhelmsen et al, 2011) and clinical (Korszun et al, 1999; Citera et al, 2000) studies. MT’s numerous physiological roles and potential therapeutic actions justify a strong need for real-time detection and monitoring of MT in the brain of laboratory animal models

Methods

Results

Conclusion