Imaging synaptic zinc release in living nervous tissue

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Zinc ions are stored in synaptic vesicles within zinc-enriched neurons.
• Previous methods for studying zinc ion release include microdialysis, autometallography, and radioactive isotope tracing.

Purpose of the Study:

• To apply the zinc fluorescence probe N-6-metoxy-p-toluensulfonamide quinoline (TSQ) as a tracer for synaptic release of zinc ions.
• To investigate the dynamics of zinc ion translocation during neuronal stimulation.

Main Methods:

• Utilized the fluorescence probe TSQ on living brain slices.
• Applied calcium-saturated ethylen diamino-tetra-acetic acid (Ca-EDTA) and sodium dethyldithiocarbamate (DEDTC) to assess membrane permeability and fluorescence changes.
• Stimulated brain slices with 50 mM potassium chloride in the presence and absence of Ca-EDTA.

Main Results:

• TSQ staining in living brain slices mimicked autometallography patterns.
• Ca-EDTA did not penetrate cell membranes, preserving fluorescence, while DEDTC partially suppressed it.
• Potassium stimulation in Ca-EDTA caused fluorescence disappearance; in its absence, it induced a transient fluorescence increase due to zinc-TSQ translocation.

Conclusions:

• TSQ is an effective probe for visualizing synaptic zinc release in real-time.
• Potassium stimulation triggers the translocation of zinc-TSQ complexes from synaptic vesicles to the extracellular space.
• This translocation leads to enhanced fluorescence, allowing for sensitive detection of synaptic zinc dynamics.