Messages are relayed from one neuron to another:Via the release of calcium from synaptic vesiclesVia the release of neurotransmitters at the synaptic cleftwith the help of voltage gated sodium channels at the axon terminalBy direct contact between dendrites and axon terminals

The process of message relay from one neuron to another involves several steps:

1. An electrical signal, or action potential, travels down the axon of the neuron. This is facilitated by the opening and closing of voltage-gated sodium channels.

2. When the action potential reaches the axon terminal, it triggers the opening of voltage-gated calcium channels. Calcium ions then flood into the neuron.

3. The influx of calcium causes synaptic vesicles, which are small sacs filled with neurotransmitters, to fuse with the membrane of the neuron.

4. The neurotransmitters are released into the synaptic cleft, which is the small gap between the neurons.

5. The neurotransmitters cross the synaptic cleft and bind to receptors on the dendrites of the next neuron. This can either trigger or inhibit the generation of a new action potential in this second neuron.

6. The neurotransmitters in the synaptic cleft are then either reabsorbed by the neuron that released them, in a process called reuptake, or they are broken down by enzymes.

7. The dendrites and axon terminals do not make direct contact. The synaptic cleft allows for the signal to be passed from one neuron to another.

So, the correct answer is: Via the release of neurotransmitters at the synaptic cleft with the help of voltage-gated sodium channels at the axon terminal.