Nanoscale diffusion in the synaptic cleft and beyond measured with time-resolved fluorescence anisotropy imaging

Area of Science:

• Neuroscience
• Biophysics

Background:

• Neural activity depends on molecular diffusion in nanoscopic spaces.
• Understanding nanoscale diffusion is crucial for brain function and signaling.

Purpose of the Study:

• To measure nanoscale diffusion in situ within ex vivo brain slices.
• To quantify molecular movement in interstitial gaps, dendritic spines, and synaptic clefts.

Main Methods:

• Utilized time-resolved fluorescence anisotropy imaging.
• Combined with two-photon excitation microscopy for nanoscale diffusivity mapping.

Main Results:

• Small molecules moved ~30% slower in brain interstitial gaps.
• Diffusion was ~70% slower inside neuronal dendrites.
• Nanodiffusion in the synaptic cleft was decelerated by ~46%.

Conclusions:

• Provides critical constraints for neurotransmitter receptor actions.
• Informs understanding of brain interstitial electrical conductance.
• Establishes limits for molecular interactions in the synaptic microenvironment.