Neurobiology of nicotine dependenceAlthough the molecular mechanisms that contribute to nicotine dependence are poorly understood, the neuromodulatory role of nicotinic cholinergic system in the central nervous system is principally implicated for it. [6] Numerous other neural pathways and neurotransmitters, including GABA, serotonin, glutamate, noradrenaline, endogenous opioid, and corticotropin