[Background] The temporal pattern of dopamine release is not necessarily the same as that of firing of midbrain dopamine neurons. Several mechanisms modifying the release at the synaptic terminals have been reported, some such nicotinic receptors (Rice and Cragg, 2004). Also, the dopamine release may locally variable within the striatum (Matsumoto 2009, Brown 2011).
[Methods] To elucidate these questions, we tried a simultaneous recording of dopamine release in the monkey caudate and putamen, during a typical Pavlovian reward task. We have previously reported the real-time detection of dopamine release using diamond microelectrodes (Yoshimi 2011), but the electrode sensitivity was easily lost in the brain. As we have succeeded in the simultaneous detection of electrically evoked dopamine release in caudate and putamen using fast-scan cyclic voltammetry on carbon-fibers (Yoshimi, Neuro2012), we next tried to detect reward-induced dopamine release at multiple locations in the striatum of an awake Japanese monkey.
[Results] Significant event-related temporal changes were detected on 12 carbon fibers. Positive responses to unexpected free reward, trial initiation signal, differential responses to the positive and negative cues, and changes to a sudden reversal of positive and negative cues were observed. The simultaneous recording at caudate-head and dorsal putamen was successful in three experimental sessions. Interestingly, some examples showed marked enhancement of responses immediately after switching the behavioral task.
[Conclusion] Real-time detection of dopamine release was successfully detected at multiple locations in the striatum of behaving monkey. This method would be useful to elucidate the modification of dopaminergic neurotransmission at the synaptic terminals, in both behaving and anesthetized primates.


[Notice] Since our monkey facility is going to be closed within a year, we welcome researchers who are willing to learn our recording techniques.