Functional activity of neurons is greatly influenced by prominent calcium signals that regulate neurotransmitter release and membrane excitability. Calcium signaling can be examined in a high-throughput manner with the use of fluorescent calcium-sensitive dyes. The relative fluorescence emitted by these dyes increases when bound to calcium and, once loaded into cells, provides a proxy for changes in cytoplasmic calcium concentrations. Image-based detection systems are available that support a wide range of formats including 96, 384, and 1536-well plates.
Changes in calcium concentration are closely tied to neuronal activity as action potentials are associated with large pre-synaptic calcium influx and a notable rise in postsynaptic calcium at excitatory synapses. This can be observed experimentally by chemical depolarization or electrical stimulation of neurons. Here, electrically evoked calcium responses are observed in the presence of various compounds.
Spontaneous calcium signals can also be observed in vitro when neurons are cultured under suitable conditions to form mature networks that exhibit spontaneous oscillations. Such oscillations are reflective of a population of neurons having synchronous network activity. This system can be used to screen pharmacological agents that alter neuronal activity, as demonstrated below using Brainxell’s Mixed Cortical Neurons (BX-0500)
