AsianScientist (Dec. 2, 2015) – Scientists have used smell to cause zebrafish to release the neurotransmitter dopamine, and in real time traced it to its circuit origin in the transparent brain of zebrafish larvae, as reported in the Journal of Neuroscience. The research showed for the first time how carbon fiber microelectrodes can be used to trace sensory-evoked dopamine in the brain of an awake small organism.
Dopamine is crucial to a broad spectrum of brain functions, and neural circuit mechanisms underlying dopaminergic regulation have been intensively studied in the past decade. Explaining the circuit origin of the dopamine release could potentially help scientists understand the circuit mechanisms underlying dopaminergic neuromodulation.
As larval zebrafish has relative simple and highly conserved dopaminergic circuitry, they can serve as an ideal vertebrate animal model to tackle this issue at a whole-brain scale. For this purpose, it is important to develop methods for monitoring endogenous dopamine release in intact larval zebrafish.
Electrochemical recording, a gold standard in monitoring dopamine release in mammals, has provided a primary understanding on how phasic dopaminergic signaling participates in various neural functions. However, since larval zebrafish have much fewer dopaminergic neurons, several orders lower than mammals previously targeted with carbon fiber microelectrodes, it is challenging to monitor dopamine release in such a small organism.
Instead, researchers led by Dr. Du Jiulin at the Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, in collaboration with Dr. Zhou Zhuan at the Institute of Molecular Medicine, Peking University used refined carbon fiber microelectrodes. They succeeded in monitoring food-evoked dopamine release in the optic tectum of zebrafish larvae, with an amperometric current as small as several to dozens of picoamperes.
Furthermore, with their tiny and transparent brains, zebrafish larva provide easy access to dopaminergic nuclei and their interconnected brain areas. By combining dopamine release monitoring, calcium imaging and laser ablation, the detected dopamine release was determined to be from pretectal dopaminergic neurons, demonstrating the potential of zebrafish larvae as a working model for thoroughly dissecting the functions and underlying mechanisms of dopaminergic systems.
The article can be found at: Shang et al. (2015) Amperometric Monitoring of Sensory-Evoked Dopamine Release in Awake Larval Zebrafish.
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Source: Chinese Academy of Sciences; Photo: Tohru-Murakami/Flickr/CC.
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