Friedlieb Ferdinand Runge (1795–1867), Heinrich F. G. Mein (1799–1864)
Over many centuries, the deadly nightshade (Atropa belladonna) and Jimson weed (Datura stramonium), among other members of the Solanaceae family, have been used with benevolent or malevolent intent. Their effects can be largely attributed to atropine, first isolated in pure form from plants in 1831 by German pharmacist Heinrich F. G. Mein. Of all the drugs contained within this book, atropine is among the least recognized yet most important in early medicine. In addition to its poisonous and medicinal properties, it has also served as a chemical tool to better understand the nervous system and for cosmetic purposes. Plant extracts containing atropine were used by Cleopatra to widen the pupils of her eyes. In the nineteenth century, this effect was studied by the German chemist Friedlieb Ferdinand Runge, whose numerous contributions to chemistry include the discovery of caffeine.
Atropine has profound effects on many target sites, including the heart, involuntary (smooth) muscles in the intestines and eye, and glands associated with the secretion of saliva and sweat as well as those in the bronchioles and stomach. To understand how atropine exerts such diverse effects, it helps to know how it works. After a nerve is stimulated, it releases a neurotransmitter, which interacts with a specialized receptor site on its target tissue to bring about an effect. This effect may cause the heart to beat faster or slower, an involuntary muscle to contract or relax, or a gland to secrete a fluid.
Outside the brain, the most important neurotransmitter is acetylcholine, which regulates involuntary functions, such as heart rate and respiration, in the autonomic nervous system (ANS) and activates muscles. Atropine acts as an antagonist, blocking acetylcholine receptors and, hence, preventing acetylcholine from activating its target. Many medicines have atropine-like effects, which are responsible for their beneficial and adverse side effects.
An abbreviated catalog of atropine’s current medical uses includes: application to the eye for ophthalmic examination and surgery; stimulation of the heart in cardiac arrest and heart block; application as an antidote in nerve-gas, insecticide, and mushroom poisoning; and reduction of excessive bowel movements and cramping. Newer atropine-like drugs are far more specific, thereby reducing undesirable side effects.
SEE ALSO Belladonna (1542), Alkaloids (1806), Scopolamine (1881), Drug Receptors (1905), Neurotransmitters (1920).
Atropine has been used in eye examinations to widen pupils but has been generally replaced by related drugs whose effects are not as long-lasting.