An optogenetic method for investigating presynaptic molecular regulation.

Area of Science:

• Neuroscience
• Molecular Biology
• Synaptic Physiology

Background:

• Efficient methods exist for studying postsynaptic regulation in the mammalian central nervous system.
• However, efficient methods for studying presynaptic function regulation are lacking.

Purpose of the Study:

• To introduce a novel optical/electrophysiological method for investigating presynaptic molecular regulation.
• To enable quantification of synaptic strength changes caused by genetic manipulations.

Main Methods:

• Utilized an optogenetic approach to selectively stimulate genetically modified presynaptic CA3 pyramidal neurons in the hippocampus.
• Measured optically-induced excitatory postsynaptic currents in unmodified postsynaptic CA1 pyramidal neurons.
• Incorporated simultaneous recordings of fiber volley amplitude to control for optical stimulation intensity.

Main Results:

• Developed a metric of synaptic efficacy comparable across experimental conditions.
• Demonstrated that inhibiting synaptotagmin 1 expression in CA3 neurons significantly reduces Schaffer collateral synapse function.
• Observed that this reduction in synaptic function was masked by conventional electrical stimulation.

Conclusions:

• The new method provides a reliable way to study presynaptic function and molecular regulation.
• This technique can reveal effects of genetic manipulations on synaptic strength that are missed by conventional methods.
• The findings expedite the understanding of molecular pathways governing presynaptic function.