Activation of the ACh receptors causes a dopamine release. This is the reason why ciggarettes are addictive, nicotine is a N-ACh receptor agonist. I dont think piracetam would work well for restless legs though. It does raise levels of acetylcholine in the synapses but it can't be by much, it doesn't really have psychoactive effects.On my mobile so can't elaborate effectively however I always was under the impression that opioid-induced RLS was due to a hypodopaminergic condition not related to ACh. Not sure how this mechanism would work on DA.