Question

Addictive drugs produce changes in one particular group of synapses that use the neurotransmitter

Answer 1

That really depends on what type of addictive drug i'll give you which i consider the most common one associated with this question "G-protein coupled Opioid receptors.". It affects the reward system in your brain all the way to Substansia Nigra.

But benzodiazepine is an addictive antideppresant drug which does not work on the sane neurotransmitter, and dues not affect the same changes.