Nicotine

Conclusion

Nicotine in the brain gives you a pleasant, relaxed feeling.

Nicotine produces these effects by mimicking the action of the neurotransmitter acetylcholine in the brain.

Nicotine is a strongly addictive substance, comparable to heroin. The body quickly develops a tolerance to nicotine, so that increasing amounts are soon needed to feel the same pleasant effects.

If the nicotine level in the body drops too low, you may experience withdrawal symptoms. These can be alleviated briefly by smoking another cigarette. Basically, smoking helps you to overcome the very feeling of restlessness that it caused in the first place.