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 as well. 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 devil’s cherries because although the berries look appetizing they are actually very toxic.
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 may cause paralysis, a coma, and respiratory failure. Deadly nightshade is definitely a plant that should be admired from a distance.
Our nervous system produces acetylcholine, which is a type of excitatory neurotransmitter. The neurotransmitter is released from the end of a stimulated neuron (or nerve cell) in order to stimulate the next neuron and transmit a nerve impulse. Acetylcholine must bind to a receptor on the second neuron 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. It 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.
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 autonomic 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 produces the opposite effects and is sometimes called the “rest and digest” system. It 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 the 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.
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.
A safe concentration of atropine is used in eye drops to make the pupils dilate so that a doctor can examine the inside of the eyes properly. (The pupil is an opening in the middle of the iris that allows light to enter the eye.) The pupils may stay dilated for several days after an atropine treatment.
It’s said that in earlier times Italian women used belladonna to dilate their pupils in an attempt to themselves look more attractive. The name “belladonna” is derived from the words meaning “beautiful lady” in Italian. The vision of the women who used atropine would probably have become blurred. The chemical inhibits accommodation—the process in which the lens changes shape to focus on objects at different distances from the eye. In addition, the women may have injured their eyes.
Food is passed along the digestive tract by wave-like contractions in the intestinal wall known as peristalsis. Acetylcholine binds to muscarinic receptors in the muscles of the intestinal wall, triggering the muscles to contract. When atropine attaches to the receptors, it blocks acetylcholine. This calms the intestinal muscles and slows the frequency and strength of muscle contractions. Atropine has therefore been used to treat conditions such as irritable bowel syndrome.
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 which surrounds the passageway that 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.
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 neurotransmitter continues to stimulate nerves. Atropine is used as an antidote to the nerve agents. It blocks the 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, or Solanum dulcamara, is sometimes known as deadly nightshade. It’s poisonous and can occasionally 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. Like the deadly nightshade, the bittersweet nightshade belongs to the plant family known as the Solanaceae.
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.
All parts of the bittersweet nightshade are poisonous. One of the toxic chemicals in the plant is solanine, which is often found in green potatoes. The potato plant is another member of the family Solanaceae. The bittersweet nightshade also contains dulcamarine, which has quite similar effects to atropine.
In a way, the bittersweet nightshade plant is more dangerous than deadly nightshade, even though it’s less poisonous. It’s more common than the deadly nightshade, so children, pets, and livestock are more likely to encounter it. It also has more attractive flowers, which may attract attention.
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.
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.
Atropa belladonna facts from the Missouri Botanical Garden
Belladonna information from the NIH (National Institutes of Health)
Atropine Ophthalmic facts from the NIH
Bittersweet nightshade identification and control from the government of King County, Washington