A new ‘dual’ in the crown for electrochemistry

nephrine play vital roles within the central nervous system. Abnormal function of these neurotransmitter systems is implicated in a range of disease states, including depression, addiction, anxiety, schizophrenia and Parkinson’s disease (see Emilien et al. 1999; Marien et al. 2004; Beaulieu and Gainetdinov 2011). Measuring the release of catecholamines in the brain requires techniques with high spatial resolution as the regions which release these substances are typically small. One technique which has proven particularly effective in furthering our understanding of the role and regulation of catecholamines is fast-scan cyclic voltammetry (FSCV). Fast-scan cyclic voltammetry utilises the innate property of catecholamines to be oxidised at low potentials to enable measurement of catecholamine concentrations with high resolution both spatially and temporally. By continuously applying high frequency voltage ramps to a carbon fibre microelectrode located in a region of interest a current ‘signature’ is obtained, allowing identification of the catecholamines being released within the vicinity of the microelectrode tip (Stamford 1990). The microelectrode is calibrated such that the output provides a measurement of catecholamine concentration at each time-point. Whilst some catecholamines have similar oxidation fingerprints, the additional use of histology and pharmacological manipulation has enabled this technique to provide significant information on the control of individual catecholamines, in particular dopamine. In the current issue, Park et al. (2011) have taken the FSCV technique into new territory by simultaneously measuring the in vivo release of both dopamine (in the anterior nucleus accumbens), and norepinephrine (in the bed nucleus of the stria terminalis) in the anaesthetised rat. Simultaneous release of catecholamines in both of these regions was accomplished through stimulation in the ventral tegmental area and substantia nigra (Park et al. 2009). FSCV microelectrode arrays have been utilised previously to perform simultaneous catecholamine measurements (e.g. Zachek et al. 2010); however, this has been limited to recording release of a single catecholamine within the same brain region. The measurement of catecholamine release in different brain regions has previously only been performed in different animals at different times, limiting result comparability. The major advantage of simultaneously measuring dopamine and norepinephrine release in the same animal (Park et al. 2011) is that it enables a direct comparison of the mechanisms controlling the release of these neurotransmitters without the potentially confounding variables associated with measurements in different animals, such as the depth of anaesthesia. Using this technique, Park et al. (2011) directly demonstrate differences in the control of norepinephrine and dopamine release in response to the same stimulation, including: (i) Slower norepinephrine release and uptake in the bed nucleus of the stria terminalis compared with that of dopamine in the anterior nucleus accumbens, as well as reduced maximal norepinephrine concentration. (ii) The presence of dopamine, but not norepinephrine, transients following pharmacological stimulation (using receptor antagonists and transport inhibitors). (iii) Elevated basal dopamine and suppressed dopamine release in the presence of amphetamine andD2 receptor antagonist (neither of which was seen with norepinephrine). (iv) Greater sensitivity of dopamine release to stimulus pulse width, as well as to inhibition of synthesis (with