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Abstract

The neurotransmitter dopamine is released from discrete axonal structures called varicosities. Its release is
essential in behaviour and is critically implicated in prevalent neuropsychiatric diseases. Existing dopamine
detection methods are not able to detect and distinguish discrete dopamine release events from multiple
varicosities. This prevents an understanding of how dopamine release is regulated across populations of
discrete varicosities. Using a near infrared fluorescent (980 nm) dopamine nanosensor ‘paint’
(AndromeDA), we show that action potential-evoked dopamine release is highly heterogeneous across
release sites and also requires molecular priming. Using AndromeDA, we visualize dopamine release at up
to 100 dopaminergic varicosities simultaneously within a single imaging field with high temporal resolution
(15 images/s). We find that ‘hotspots’ of dopamine release are highly heterogeneous and are detected at
only ~17% of all varicosities. In neurons lacking Munc13 proteins, which prime synaptic vesicles,
dopamine release is abolished during electrical stimulation, demonstrating that dopamine release requires
vesicle priming. In summary, AndromeDA reveals the spatiotemporal organization of dopamine release.