An action potential releases neurotransmitter from a neuron by opening which channels?

Calcium channels.

Explanation:

The  arrival of action potential at the presynaptic neuron, cause the opening of Ca+ channels, at the presynpatic neuron membranes. This leads to influx of Ca+ . The latter caused  the Acetycholine contained vesicles in the presynaptic  neuron to migrate to the tip of the presynaptic neurons, and  fused with the neuronal membrane to  empty their contents into the synaptic cleft.

i would say the prokaryotic cells the prokaryotic cells are less complex, are usually found only in unicellular organisms and have more limited capabilities than eukaryotic cells.