<unk>  is a potent parasympathomimetic alkaloid found in the nightshade family of plants (Solanaceae) and a stimulant drug.<unk>  is a<unk> c acetylcholine receptor (nAChR) agonist, except at nAChRα9 and nAChRα10 where it acts as an antagonist. It is made in the roots of and accumulates in the leaves of the nightshade family of plants.
It constitutes approximately 0.6–3.0% of the dry weight of tobacco and is present in the range of 2–7 µg/kg of various edible plants.
It functions as an antiherbivore chemical; consequently,<unk>  was widely used as an insecticide in the past
and<unk>  analogs such as imidacloprid are currently widely used.
In lesser doses (an average cigarette yields about 2 mg of absorbed<unk> , the substance acts as a stimulant in mammals, while high amounts (50–100 mg) can be harmful.
This stimulant effect is a major contributing factor to the addictive properties of tobacco smoking.
Nicotine
Heroin
N-Nitrosonornicotine
Cannabis 
Nicotinyl alcohol
Opiate
Methamphetamine
Benzocaine 