Spatial and temporal scales of dopamine transmission

Dopamine is often portrayed as a diffuse, slow neuromodulator, yet such signalling cannot explain its broad and sometimes rapid roles. Here, Liu, Goel and Kaeser review recent insights into dopamine release and receptors and present a new framework - the domain-overlap model - for dopamine signalling. Dopamine is a prototypical neuromodulator that controls circuit function through G protein-coupled receptor signalling. Neuromodulators are volume transmitters, with release followed by diffusion for widespread receptor activation on many target cells. Yet, we are only beginning to understand the specific organization of dopamine transmission in space and time. Although some roles of dopamine are mediated by slow and diffuse signalling, recent studies suggest that certain dopamine functions necessitate spatiotemporal precision. Here, we review the literature describing dopamine signalling in the striatum, including its release mechanisms and receptor organization. We then propose the domain-overlap model, in which release and receptors are arranged relative to one another in micrometre-scale structures. This architecture is different from both point-to-point synaptic transmission and the widespread organization that is often proposed for neuromodulation. It enables the activation of receptor subsets that are within micrometre-scale domains of release sites during baseline activity and broader receptor activation with domain overlap when firing is synchronized across dopamine neuron populations. This signalling structure, together with the properties of dopamine release, may explain how switches in firing modes support broad and dynamic roles for dopamine and may lead to distinct pathway modulation.

Automated summary

Dopamine is a prototypical neuromodulator that controls circuit function through G protein-coupled receptor signaling. While dopamine is often described as a diffusive and slow signaling molecule, recent studies suggest that certain functions of dopamine require spatiotemporal precision.