Real time measurement of stimulated dopamine release in the conscious rat using fast cyclic voltammetry: dopamine release is not observed during intracranial self stimulation.

Fast cyclic voltammetry (FCV) was used to measure real time release of electrically stimulated endogenous dopamine in the nucleus accumbens (NAc) of conscious freely moving rats for up to 17 days. The method of electrode construction, implantation, electrical stimulation and recording of changes of extracellular dopamine concentration in the conscious rat are described. Rats trained on a continuous reinforcement schedule to perform intracranial self stimulation (ICSS) were implanted with electrodes for FCV. During ICSS, no faradaic signal was observed at an electrode implanted in the NAc. Decreasing the intensity of the stimulating current abolished ICSS, increasing the stimulating current disrupted ICSS. Operator delivered electrical stimulations using currents greater than those needed for ICSS yielded dopamine signals. It is concluded that during ICSS, sufficient dopamine does not reach the extracellular fluid space to yield a faradaic signal detectable by FCV.