Dynamic changes in accumbens dopamine correlate with learning during intracranial self-stimulation.

Dopamine in the nucleus accumbens (NAc) is an important neurotransmitter for reward-seeking behaviors such as intracranial self-stimulation (ICSS), although its precise role remains unclear. Here, dynamic fluctuations in extracellular dopamine were measured during ICSS in the rat NAc shell with fast-scan cyclic voltammetry at carbon-fiber microelectrodes. Rats were trained to press a lever to deliver electrical stimulation to the substantia nigra (SNc)/ventral tegmental area (VTA) after the random onset of a cue that predicted reward availability. Latency to respond after cue onset significantly declined across trials, indicative of learning. Dopamine release was evoked by the stimulation but also developed across trials in a time-locked fashion to the cue. Once established, the cue-evoked dopamine transients continued to grow in amplitude, although they were variable from trial to trial. The emergence of cue-evoked dopamine correlated with a decline in electrically evoked dopamine release. Extinction of ICSS resulted in a significant decline in goal-directed behavior coupled to a significant decrease in cue-evoked phasic dopamine across trials. Subsequent reinstatement of ICSS was correlated with a return to preextinction transient amplitudes in response to the cue and reestablishment of ICSS behavior. The results show the dynamic nature of chemical signaling in the NAc during ICSS and provide new insight into the role of NAc dopamine in reward-related behaviors.