Real-time measurements of phasic changes in extracellular dopamine concentration in freely moving rats by fast-scan cyclic voltammetry.

1. Introduction Rapid, transient changes in extracellular dopamine concentrations following salient stimuli in freely moving rats have recently been detected using fast-scan cyclic voltammetry (1,2). This type of neurotransmission had not been previously observed (for any neurotransmitter), but has been implicated by electrophysiological studies. Schultz et al. (3) reported synchronous burst firing of midbrain dopaminergic neurons following presentation of liquid reinforcers or associated cues. Such firing patterns would predictably produce transient (lasting no more than a few seconds), high concentrations (high nanomolar) of extracellular dopamine in terminal regions. This phasic dopaminergic neurotransmission has been heavily implicated in associative learning and reward processing, and therefore may prove essential in understanding the reinforcing actions of drugs of abuse. Fast-scan cyclic voltammetry is a real-time electrochemical technique that can detect dopamine by its redox properties. It is capable of monitoring monoaminergic neurotransmission in the brain on a subsecond time scale while providing chemical information on the analyte. This chapter describes how the properties of fast-scan cyclic voltammetry make it uniquely suitable for making chemical measurements of phasic dopaminergic neurotransmission in freely moving animals. To emphasize the potential of this technique, three examples of its use are highlighted. First we describe experiments testing