The Monitoring of Neurochemical Dynamics in Zebrafish Retina using Fast Scan Cyclic Voltammetry

Abstract

Dopamine is a crucial neurotransmitter important for several behavioral, pharmacological, and disease states. Cocaine, amphetamine, and other psychostimulants elicit their effects by increasing dopamine in the extracellular space, while Parkinson’s disease is caused by the lack of extracellular dopamine due to the death of dopaminergic neurons. Techniques such as fast scan cyclic voltammetry (FSCV) have been utilized to measure extracellular dopamine and other neurotransmitters through the application of a triangle waveform, which can oxidize and, subsequently, reduce neurotransmitters at the surface of the electrode, producing a cyclic voltammogram where peak oxidative current is proportional to concentration. Utilizing FSCV with carbon fiber microelectrodes (CFMEs) is useful because the carbon electrodes are biocompatible and have both high temporal and spatial resolution. This makes the electrode amenable for the detection of neurotransmitters on a fast subsecond timescale comparable to the fast, phasic firing of dopaminergic neurons. Preliminary studies have illustrated the utility of CFMEs with FSCV for neurochemical detection in zebrafish (Danio rerio). CFMEs were implanted into zebrafish brain preserved in oxygenated buffer ex vivo with a micromanipulator. The electrodes were also inserted into zebrafish retina for the measurement of neurotransmitter release. The release of neurotransmitters was stimulated by the application of potassium chloride (KCl), amphetamine and cocaine, or electrical stimulation. Significant differences in dopamine levels were observed between wildtype control animals and hyperglycemic (diabetic) zebrafish. Moreover, behavioral assays such locomotor measurement displayed cognitive defects in hyperglycemic animals in addition to the thinning of the retina, which correlated to significant increases in extracellular dopamine in comparison to wildtype animals. Further work includes the examination of raclopride to increase extracellular dopamine, selective serotonin reuptake inhibitors to monitor serotonin, and desipramine to measure norepinephrine dynamics. This study allows for the further investigation of the neurochemical and behavioral effects of hyperglycemia in zebrafish. Future work will extend to the analysis of other monoamines such as serotonin and other dopamine metabolites. Support or Funding Information NIH STTR: 1R41NS113702‐01 Raw for the detection of dopamine in zebrafish retina after potassium chloride stimulation.

Timed Electrodeposition of PEDOT:Nafion onto Carbon Fiber-Microelectrodes Enhances Dopamine Detection in Zebrafish Retina

“… 62 Each electrode was pre- and post-calibrated using 1 μ M DA solution before measuring the KCl-stimulated DA release in order to extrapolate released concentrations based on relative peak oxidative currents. 63 , 64 We measured average released DA concentrations of 0.51 ± 0.20 μ M (n = 3) in zebrafish retina. These evoked DA concentrations in zebrafish retina are similar to levels in whole brain (0.49 ± 0.13 μ M) and sagittal brain slices (0.59 ± 0.28 μ M).…”

Analytical strategies in neurotransmitter measurements: A mini literature review

“…Mauterer et al used ex vivo FSCV to detect DA in the nucleus accumbens in rodent brain slices (Mauterer et al, 2018). Zebrafish retinal neurochemical dynamics have also been monitored via FSCV (Zestos et al, 2020…”

“…Mauterer et al used ex vivo FSCV to detect DA in the nucleus accumbens in rodent brain slices (Mauterer et al, 2018). Zebrafish retinal neurochemical dynamics have also been monitored via FSCV (Zestos et al, 2020). Weese‐Myers et al used FSCV to characterize electroactive amino acids such as cysteine, methionine, histidine, tryptophan, and tyrosine (Weese‐Myers & Ross, 2021).…”