Monitoring Rapid Chemical Communication in the Brain
Year: 2008
Type: review
Abstract: Neurotransmitters are chemicals that are secreted by neurons and relay messages to target cells.The goal of in vivo electrochemistry is to provide a real-time view of neurotransmitters in the extracellular space of the brain.This may be done in brain slices or the intact brain of anesthetized animals to probe the basic functions that regulate neurotransmitter levels.In other experiments, the measurements need to be made in the brain of behaving animals so that correlations of neurotransmitter fluctuations and specific behaviors can be made.For the neurotransmitter dopamine this can be accomplished today by chemical sensing of this neurotransmitter with fast scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes.Dopamine is an important target because it is a central player in the brain 'reward' system, although its precise function is not understood.Proposed roles for dopamine in reward have included the mediation of hedonia (pleasure) 1 , a messenger of incentive salience (wanting) 2 , or an error signal that promotes the learning associated with goal-directed behavior 3,4 .These multiple interpretations of dopaminergic function have arisen because, until recently, a realtime view of dopamine and its actions in an awake, behaving animal was unavailable.At the same time, new electrochemical technologies are being developed to measure other neurotransmitter actions.Electrochemical approaches are well suited for this application because they allow a neurotransmitter to be measured with high time resolution, enabling its precise role in the execution of behavioral tasks to be investigated.In this review we will describe current methods to detect neurotransmitters and monitor their concentration dynamics within neural tissue.The requirements for these methods are quite stringent.They need to be sufficiently selective so that the measured responses are unequivocally due to a specific molecule.They need to be sufficiently sensitive that they can detect these substances in the physiological range.The best established methodologies are for dopamine, so the majority of the applications of the methods described herein will involve this neurotransmitter.As will be seen, the goals in measuring neurotransmitter functions are diverse.On one hand, investigators are unraveling the mechanisms that control neurotransmitter concentrations.These studies range from examining biochemical synthesis to metabolism.On the other hand, investigators are questioning how the neurotransmitter interacts with its receptors and what message it conveys.Yet a third major interest is the role of a neurotransmitter in specific behaviors.To obtain a complete view of neurotransmission and information processing, chemical sensors need to be combined with traditional neurochemical tools.We will illustrate this approach with some specific examples. Neurotransmitters and brain functionIn a recent book, the 2000 Nobel Prize winner Eric Kandel reviewed the scientific findings that lead to our current understanding of the brain 5 .As this book clearly shows, understanding the brain is a challenging research field, but significant progress is being made through the combined input of investigators from multiple disciplines.Kandel notes that three central principles, which emerged in the early twentieth century, form the building
Source: Chemical Reviews
DOI: 10.1021/cr068081q
Institution: University of North Carolina at Chapel Hill
Language: English
Subfield: Electrochemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2084256175