I'll spoon feed you just once.
Basis of smoking cessation is to stimulate nicotinic acetylycholine receptors in the CNS to stimulate Mesolimibic Dopaminergic response.. the reward center or the brain.
Topamax' main site of action however is not the dopaminergic rather GABA stimulation. But it's not fully elucidated how Topmax aids in smoke cessation. Here are hypothesis.
Topamax can decrease urge for alcohol consumption which is associated with smoking. Scientists also believe Topamax has dopaminergic acitivities..