Question

One of the most striking discoveries of 20th-century biology was that drugs work by imitating naturally occurring substances in our bodies. In the case of chemicals that act on the nervous system the naturally occurring agents are called neurotransmitter substances. There are many ways that such interactions can occur, however. How does a drug that imitates a neurotransmitter work? How does a drug that inhibits the action of a neurotransmitter work?

Answer 1

Such drugs work in the brain by tapping into the brain's communication system and interfering with the way nerve cells normally send, receive, and process information. Some drugs, such as marijuana and heroin, can activate neurons because their chemical structure mimics that of a natural neurotransmitter.

Most drugs act by being either agonists or antagonists at receptors that respond to chemical messengers such as neurotransmitters. An agonist binds to the receptor and produces an effect within the cell. An antagonist may bind to the same receptor, but does not produce a response, instead, it blocks that receptor to a natural agonist.

Drugs that inhibit the action neurotransmitters such as atropine inhibits the muscarinic actions of acetylcholine on structures innervated by postganglionic cholinergic nerves, and on smooth muscles, which respond to endogenous acetylcholine but are not so innervated. Some drugs disrupt more than one type of neurotransmitter. Cocaine, for example, attaches to structures that regulate dopamine, leading to increases in dopamine activity and producing euphoria; it also produces changes in norepinephrine and glutamate systems that cause stimulant effects.