The leaves of Atropa belladonna contain tropane alkaloids such as atropine, scopolamine, and hyoscyamine, which cause delirium (acute confusional state) and hallucinations (perception in the absence of external stimulus).
Nicotine stimulates the release of epinephrine from the adrenal gland.
Amphetamines are stimulant type of drugs used in the treatment of depression, narcolepsy (excessive sleepiness), and attention deficit hyperactivity disorder (ADHD). Sedatives and hypnotics are the drugs that are commonly called tranquilizers, sleeping pills or sedatives. They have a relaxing, calming effect and are often used to treat anxiety and insomnia (sleeplessness).
Cocaine interferes with the transport of the neurotransmitter dopamine.