The accumulation of nicotine during the period of intoxication provokes the inactivation of the receptors and a reduction of pleasure. This phase is followed by a fall of the concentration in nicotine during the night, which implies a reactivation of the receptors. On waking up, the return of all receptors to an active state abnormally rises the neurotransmission. Then, the smoker suffers from withdrawal symptoms which makes him smoke a first cigarette that gives him maximum pleasure.