Technically, nicotine is not significantly addictive, as nicotine administered alone does not produce significant reinforcing properties. However, only after coadministration with an MAOI, such as those found in tobacco, nicotine produces significant behavioral sensitization, a measure of addiction potential. This is similar in effect to amphetamine.
Modern research shows that nicotine acts on the brain to [...]

 
By binding to nicotinic acetylcholine receptors, nicotine increases the levels of several neurotransmitters – acting as a sort of “volume control”. It is thought that increased levels of dopamine in the reward circuits of the brain are responsible for the euphoria and relaxation and eventual addiction caused by nicotine consumption. Nicotine has a higher affinity [...]

 
Nicotine is optically active, having two enantiomeric forms. The naturally-occurring form of nicotine is levorotatory. The dextrorotatory form, (+)-nicotine, has only one-half the physiological activity of (–)-nicotine. It is therefore weaker in the sense that a higher dose is required to attain the same effects. The salts of (+)-nicotine are usually dextrorotatory.
As nicotine enters the [...]