Belladonna or Deadly Nightshade Dangers and Atropine Uses
A Deadly Plant and a Useful Chemical
The deadly nightshade plant, also known as belladonna, is so poisonous that eating as few as two berries can kill a child. The plant contains atropine and other dangerous alkaloid chemicals, including scopolamine and hyoscyamine. Despite its toxicity, when used in small quantities atropine has important medical applications.
Deadly nightshade is native to Europe, North Africa and Western Asia, but the plant grows in North America, too. Its scientific name is Atropa belladonna. All parts of the plant are poisonous.
The flowers of the deadly nightshade plant are bell-shaped and are purple and green in color. The large, oval leaves have pointed tips. Unripe berries are green. As they ripen, the berries become black, shiny and beautiful. The deadly nightshade is sometimes called black cherry or devil’s cherries, because although the berries look appetizing they are actually very toxic.
Effects of Deadly Nightshade Poisoning
Not only is eating any part of the deadly nightshade dangerous, but simply touching the plant can be harmful if the skin has cuts. There are many possible symptoms of poisoning, including:
- rapid heartbeat
- dry mouth
- slurred speech
- light sensitivity
- blurred vision
- inability to urinate
- loss of balance
- flushed skin
- a rash
- memory loss
Severe poisoning can cause paralysis, a coma and respiratory failure. Deadly nightshade is definitely a plant that should be admired from a distance.
Devil's Cherries or Deadly Nightshade Berries
How Does Atropine in Deadly Nightshade Affect the Body?
Our nervous system produces acetylcholine. This chemical is a type of excitatory neurotransmitter – a substance released from the end of a stimulated nerve cell in order to stimulate the next nerve cell and transmit a nerve impulse. The acetylcholine must bind to a receptor on the second nerve cell in order to do its job. One type of acetylcholine receptor is known as a muscarinic receptor.
Atropine binds to muscarinic receptors, stopping acetylcholine from joining to the receptors. Atropine can therefore stop the transmission of nerve impulses. Muscarinic receptors are also present in smooth muscle, so atropine can inhibit the activity of muscles as well as nerve cells. Smooth muscle is found in our organs and blood vessels.
Effect on the Parasympathetic Nervous System
Our autonomic nervous system - the part of the nervous system that we can't control voluntarily - consists of two divisions.
- The sympathetic division of the nervous system prepares our bodies for emergencies. It’s often said to stimulate the “flight or fight” response. It causes the heart to beat faster, the breathing rate to increase and the pupils to dilate. It also inhibits digestion.
- The parasympathetic division of the nervous system produces the opposite effects to the sympathetic system and is sometimes called the “rest and digest” system. The parasympathetic system relaxes the body, slows the heartbeat and breathing rate, constricts the pupils and stimulates digestion.
Atropine interferes with the action of the parasympathetic nervous system because the nerve cells of this system release acetylcholine. Atropine blocks the muscarinic receptors of the system, preventing acetylcholine from transmitting nerve impulses. Without the action of parasympathetic nerves, the body is unable to counteract sympathetic stimulation and the balance between sympathetic and parasympathetic stimulation is destroyed.
Atropine and the Heart
Eating atropine inside a part of the deadly nightshade plant is very dangerous, but small amounts of atropine used in medications can be helpful. Atropine used as a medicine must be prescribed by a doctor.
Atropine injections are given to speed up a very slow heartbeat. The atropine blocks the action of the vagus nerve. This nerve is part of the parasympathetic nervous system and slows down the heartbeat. When the action of the vagus nerve is inhibited by atropine, the heart will beat faster.
Atropine and the Eyes
Atropine is also used in eye drops to make the pupils dilate so that a doctor can examine the inside of the eyes properly. The pupils stay dilated for several days. It’s been reported that in earlier times some Italian women would use belladonna to dilate their pupils, making them look more attractive. The name “belladonna” means “beautiful lady” and supposedly comes from this use. The women’s vision would also have become blurred, since atropine inhibits accommodation – the process in which the lens changes shape to focus on objects at different distances from the eye.
Digestive Tract Effects
Food is passed along the digestive tract by wave-like contractions in the intestinal wall called peristalsis. Acetylcholine binds to muscarinic receptors in the muscles of the intestinal wall, triggering the muscles to contract. Atropine binds to these receptors and blocks acetylcholine. This calms the stomach and intestinal muscles and slows the frequency and strength of muscle contractions. Atropine has therefore been used to treat conditions such as irritable bowel syndrome.
Effects on the Urinary Bladder and Urination
The parasympathetic nervous system triggers urination by two methods. It stimulates the muscle in the urinary bladder wall to contract, which causes urine to be pushed out of the bladder. In addition, it relaxes the sphincter muscle that surrounds the passageway which transports urine out of the bladder. When the sphincter muscle contracts, the passageway is closed and the bladder is able to fill with urine. The parasympathetic nervous system counteracts this process, allowing urine to be released.
Since atropine inhibits the activity of the parasympathetic nervous system it reduces urination. Atropine also inhibits spasms of the urinary bladder. These abilities help some urinary system problems.
Other Medical Uses of Atropine
Atropine decreases the production of body secretions, including saliva, mucus and sweat. It's been used in cough syrups to help clear the airways.
Atropine is sometimes used as a sedative. It’s known that acetylcholine is used as a neurotransmitter in the brain as well as in the parasympathetic nervous system, which is why atropine can affect brain functions when it interferes with the action of acetylcholine.
Inhibiting Chemical Weapons
Most chemical weapons that act on nerves belong to a group of chemicals known as organophosphates. These chemicals prevent acetylcholine from being broken down once it has done its job, so the acetylcholine continues to stimulate nerves. Atropine is used as an antidote to these nerve agents, since it blocks acetylcholine receptors, preventing the acetylcholine from reaching the nerves. Military personnel may carry an atropine auto-injector to protect themselves from chemical weapons.
The Bittersweet Nightshade Plant
The bittersweet nightshade, Solanum dulcamara, is sometimes known as deadly nightshade. It's poisonous and can sometimes be deadly, but it's not as toxic as the true deadly nightshade. An alternate name for the plant is woody nightshade. It's a perennial vine which is native to Europe and Asia but is widespread in North America.
The attractive flowers of the bittersweet nightshade have blue or purple petals. The petals are curved backwards, revealing a yellow or orange center. The berries are green when unripe and bright red when ripe. The leaf has one large lobe and a pair of small lobes at the base.
Toxins in Bittersweet Nightshade
All parts of the bittersweet nightshade are poisonous. One of the toxic chemicals in the plant is solanine, which is also found in green potatoes. The plant also contains dulcamarine, which has quite similar effects to atropine.
In a way, the bittersweet nightshade is more dangerous than deadly nightshade, even though it's less poisonous. It's more common than deadly nightshade, so children, pets and livestock are more likely to encounter it. Eating bittersweet nightshade can potentially kill children and animals, but human deaths are quite rare. A doctor or veterinarian must always be consulted if a person or animal has eaten the plant, however.
Plants to Admire and Avoid
The deadly and bittersweet nightshades are attractive and interesting plants, but they need to be treated with a great deal of respect. I often see the bittersweet nightshade during my walks and always admire its pretty flowers and berries. I enjoy observing and photographing the plant, but I keep its potential dangers in mind.
Toxic plants can have benefits, such as the production of atropine and other medically useful chemicals. It's very important that children (and adults) avoid touching the plants or eating any part of them, however. Younger children should be monitored when they are out of doors. Children that are old enough to leave the home on their own should be taught how to identify poisonous plants that they may encounter. Nature is often beautiful and offers us wonderful benefits, but it can sometimes be dangerous.
References and Further Reading
© 2010 Linda Crampton