MicroRNA-Mediated Inhibition of Excitatory Postsynaptic Currents in Mouse Hippocampal Slices

Take mouse hippocampal brain slices containing CA3 neurons infected with a recombinant viral vector.

The viral genome expresses a light-activated channel tagged with a fluorescent reporter and a microRNA that downregulates the expression of voltage-gated calcium channels.

Place a slice in a recording chamber under dark conditions. Using a microscope, identify the fluorescent CA3 neurons.

Patch a recording electrode onto a CA1 neuron that receives input from infected CA3 neurons. Rupture the membrane to record intracellular ionic currents.

Apply an inhibitor to block inhibitory neurotransmitter receptors, allowing only excitatory signals.

Using light pulses, stimulate the light-activated channels in the infected CA3 neurons, generating action potentials.

In uninfected mice, the action potential activates voltage-gated calcium channels, causing a calcium ion influx that triggers neurotransmitter release. The neurotransmitters trigger excitatory postsynaptic currents, or EPSCs, in the CA1 neurons.

In infected mice, the microRNA-mediated reduction of voltage-gated calcium channels results in EPSC inhibition.