Nicotine mimics the action of a natural neurotransmitter: acetylcholine. Its presence in the brain activates dopaminergic neurons: the reward circuit.
Tobacco addiction is developing very rapidly, due to the fact that nicotinic receptors are present on the neurons of the ventral tegmental area that project their endings in the nucleus accumbens (the center of reward, pleasure ...) . Repeated nicotine stimulation in smokers therefore increases the release of dopamine into the nucleus accumbens. However, the chronic smoker maintains, between each cigarette, a sufficient nicotine concentration to deactivate the receptors and to slow down their renewal. Hence the tolerance and reduction of the pleasure felt by consuming nicotine and the addiction increases.
