Ultrastructural Dynamics of Dopaminergic Presynaptic Release Sites revealed by Cryo-correlative Light and Electron Microscopy

Dopaminergic neurons are fundamental in governing motivation, movement, and many aspects of cognition. The targeted modulation of dopaminergic signaling serves as a cornerstone in developing therapeutic interventions for conditions such as Parkinsons disease, schizophrenia, and addiction. Despite the pivotal role of dopaminergic neurons, the ultrastructure and associated dynamics of dopaminergic synapses remain poorly understood. Here, we develop and utilize a cryo-correlative light and electron microscopy process chain to investigate the micro- to nanoscale architecture and organelle content of dopaminergic presynaptic release sites. Using cryo electron tomography, we identify several protein complexes crucial to dopaminergic function and we utilize subtomogram averaging to resolve in situ assemblies of the TRiC/CCT chaperone and vacuolar-type ATPase. Lastly, we find that pharmacological treatments using either dopamine or the dopamine D2 receptor antagonist, haloperidol, bidirectionally modulate vesicular content, mitochondrial size and calcium phosphate deposition. These findings contribute to our general understanding of the composition and ultrastructural dynamics of dopaminergic presynaptic release sites and provide a methodological platform for further studies of the structure and cell biology of dopaminergic neurons and their responses.