What specific part of the neuron communicates with a target cell and serves as the secretory region of the cell?

Answer is axon terminal.

Explanation:

The axon terminal is the end and the sending part of synapses. They are very important in releasing the neurotransmitters of the pre-synaptic cell and send them to post-synaptic dendrites found on other neurons.

This is possible because, the axon terminal vesicles full of neurotransmitters.

I think The answer is axon terminal