The major agent present in tobacco is nicotine. It is a psychotropic agent which mimics acetylcholine action in the cholinergic receptors, which in turn exert stimulatory effects on the mesolimbic dopaminergic function. Nicotine can increase DA outflow in the nucleus accumbens and corpus striatum. It excites additional neuronal firing and increases bursting activity of the DA neurons situated in the (SNc) and (VTA). Smoking also increases inflammatory hormone prostaglandin E2 production. A repeated usage will reinforce the effects, thus leading to addiction.

Nicotine is also associated with changes of the sperm membranes, receptors, and damage to the sperm DNA. By mimicking acetylcholine, it will bind to a sperm cholinergic receptor that is responsible for the sperm’s fertilizing properties.

Smoking will also result in abnormal increases of the seminals’ leukocyte counts by almost doubling it. An increased seminal leukocytic counts (white blood cells) is a clear sign of an ongoing inflammation within the reproductive tract, leading to poor quality and quantity of the semen. Smoking related oxidization stress explains the reduced sperm fertilizing capacity and increased oxidative damage to the sperms DNA among male smokers.

High levels of dopamine, serotonin and GABA nervous function will help one overcome nicotine addiction.