One feature enabled by the μLP chamber is the ability to investigate synapse-to-soma/nucleus signaling. For example, during LTP induction, local synaptic activation at the plasma membrane causes rises in postsynaptic calcium that propagate to the soma and stimulate new transcription. To test the ability to detect such events using our device, we locally perfused glutamate then monitored dendritic and somatic calcium dynamics, using the fluorescent calcium indicator dye, Fluo-4 NW. Monitoring the same neuron over time, we stream acquired images before and after vehicle and glutamate (200 μM) perfusion within the channel; TTX (1 μM) was included to the postsynaptic and presynaptic compartments to prevent neuronal spiking. While vehicle perfusion in the channel did not change calcium levels appreciably (Figure 6A and Movie S1), perfusion with glutamate (∼3 min) on the same dendrite led to a rapid increase in calcium at the perfused dendrite and a slower rise in calcium at the cell body (Figure 6B and Movie S2). Post-hoc immunostaining for MAP2 shows the integrity of the neuron following the perfusion (Figure 6C). Thus, the μLP chamber can also be used to investigate calcium dynamics locally and globally.
