Neurotransmitter Uncaging

Understanding how individual neurons integrate the thousands of synaptic inputs they receive is critical to understanding how the brain works (1). It is undisputable today that dendrites with their characteristic non-linear integration of inputs play critical role in information processing in the brain. However, studying complex spatiotemporal patterns of synaptic inputs is still very challenging.

One of approaches in studies of synaptic integration in dendrites is photolysis of caged glutamate and systematically probing the dendrite’s voltage response to differential spatial and temporal pattern that mimics synaptic input activity (2,3).

Bruker offers several technical developments for this area of research. Both 1-photon and 2-photon neurotransmitter uncaging at multiple spines can be achieved. Uncaging is performed simultaneously with imaging thanks to dual optical light paths (3,4).

Bruker also offers holographic uncaging with random 3D access with its Neuralight 3D spatial light-modulator (SLM) product. It is a liquid crystal device that generates holographic patterns of illumination to form multiple focal points or arbitrary shapes. This device can produce truly simultaneous illumination at multiple locations. To facilitate fast volumetric imaging while performing 3D neurotransmitter uncaging Bruker implemented optically corrected electro-tunable lens (ETL).

Bruker support this application with proprietary Prairie View software. Software allows for defining, synchronizing, and calibrating laser illumination, galvanometer mirror positioning, electrophysiology, and fluorescence measurements integration.

The Ultima 2Pplus and a Bruker spatial light modulator (SLM) proved useful for investigating the behavior of activated synapses across multiple basal dendritic branches under quiescent and in vivo-like conditions in a recent publication. In their paper, "Probing Action Potential Generation and Timing under Multiplexed Basal Dendritic Computations Using Two-photon 3D Holographic Uncaging," Shulan Xiao, Saumitra Yadav, and Krishna Jayant observe action-potential precision, noise-enhanced responsiveness, and improved temporal resolution under high conductance states. Results revealed multiplexed dendritic control of somatic output amidst noisy membrane-voltage fluctuations and backpropagating spikes.