A neurotransmitter, acetylcholine is similar to dopamine and serotonin. Acetylcholine, abbreviated to Ach, is used at neuromuscular junctions. Our nervous system is used by neurotransmitters, which are specific molecules, to transmit signals to neurons. Even the neurons transmit messages among them through neurotransmitters. These molecules are also used to send messages by the neurons to muscles.
In fact, acetylcholine is among the most important neurotransmitters present in the human body. It has a vital role in our brain as it helps to enhance memory, concentration, and cognition, in addition to the augmenting functioning of the muscles.
Besides being among the commonest neurotransmitters present in the human body, acetylcholine also happens to be the first neurotransmitter discovered by scientists. The credit of discovering this neurotransmitter goes to an English pharmacologist and physiologist named Henry Hallett Dale. While Dale discovered acetylcholine in 1916, later a German-born pharmacologist and psycho biologist named Otto Lowei confirmed the presence of this neurotransmitter in the human body. The discovery of acetylcholine was considered to be an important progression and, hence, in 1936 both these scientists were presented with the Nobel Prize in Physiology/Medicine.
While scientists know a lot about two similar neurotransmitters – dopamine and serotonin, they are still in the dark regarding several aspects of acetylcholine. Hence, it is not surprising that the nickname of this neurotransmitter denotes “vague stuff”. Nevertheless, acetylcholine derives its names from the fact that this neurotransmitter has an effect on the vagus nerve in the hippocampus hemisphere of our brain.
Like all other neurotransmitters, acetylcholine is also a chemical compound. This neurotransmitter gets its name from two substances that amalgamate it – while acetyl CoA is an enzyme, choline is a nutrient.
Here are a few important features of this vital neurotransmitter. Among all its functions, acetylcholine plays a very crucial role in the memory. This neurotransmitter is also essential for converting temporary memories into lasting memories. As we grow older, the levels of acetylcholine in our body tend to decline resulting to some memory loss. In fact, we consider some memory loss at old age to be normal, but this is mainly due to the declining level of acetylcholine. In other words, the cognitive decline suffered by aged people is owing to the drop in acetylcholine level as we age.
Acetylcholine is produced in the hippocampus of our brain – the region of the brain that is said to be its memory hub. Hence, it is not surprising that in the initial stages of dementia and Alzheimer’s usually the hippocampus region starts degenerating first.
When the level of acetylcholine begins to decline, the initial symptoms include a drop in verbal memory, visual memory, spatial orientation as well as processing speed. As the visual memory starts declining, an individual will find it difficult to keep in mind what he/she has read. At the same time, they will find it difficult to form reflections in their mind, remember where different things are or even recall faces.
When one’s verbal memory begins to go, he/she will in general forget words or even lose their chain of thoughts during a conversation.
The neurotransmitter acetylcholine offers numerous health benefits – primary among them is to support and augment our memory. Deficiency of this neurotransmitter in the hippocampus, which is also called the memory hub of the human brain, is associated with diseases like Alzheimer’s and dementia.
It is worth mentioning here that a drug called scopolamine damages the memory in humans and animals to such extent that one fails to acquire new information. It has been found that when the supply of acetylcholine is disrupted to the monkey’s brain (hippocampus, neocortex) they are unable to acquire new factual information (also known as discrimination learning). At the same time, it also makes them forget things – something similar to amnesia in human beings.
Enhanced alertness and attention
Acetylcholine has been found to work to enhance alertness and attention. In the past, it was believed that this neurotransmitter is primarily important because it helps in learning and is responsible for short-term or temporary memory. However, findings of studies undertaken recently have shown that acetylcholine also plays a vital role in attention.
During animal studies, it was found that acetylcholine helped rats not only to improve their task performance, but also augmented their memory.
In another study undertaken on humans, it was found that 60 adult women in the age group of 40-60 who were given acetylcholine supplements (CDP-choline) continuously for 28 days showed marked improvement in their attention. Acetylcholine is vital for enhancing alertness, especially when a person wakes up.
This neurotransmitter also works to reduce inflammation. It has been established that the influence of acetylcholine on reducing inflammation is significant. Incidentally, even a pathway is named after acetylcholine – it is known as “The cholinergic anti-inflammatory pathway”.
When we sustain an injury or suffer from any infection, the cells of our immune system produce inflammatory cytokines. This result in a series of effects including deploying inflammatory cells to the infection site with a view to restrain it. When this happens, the cholinergic anti-inflammatory pathway causes a breaking effect on the response of the immune system, which, in turn, shields our body against any potential harm. In fact, damages can happen if the inflammatory response which is localized at the infection spot spread further than the local tissues. In such instances, the outcome is damage or toxicity of the lungs, kidneys, liver and several other organs.
When the vagus nerve in the hippocampus region of the brain is activated, it uses its anti-inflammatory exploits through acetylcholine. Any decline in the activity of the vagus nerve may result in inflammatory bowel disease (IBD) because in such case acetylcholine activation would not take place leading to lesser anti-inflammatory activity.
During experiments on animals, it was found that an increase in acetylcholine level actually decreased the mucosal inflammation in the gut. It has been found that acetylcholine reduces IL 1B, IL-6, TNF-a and various other cytokines favouring inflammation in various inflammatory conditions, such as the inflammatory bowel disease or IBD.
When we are awake more acetylcholine is released in the brain. In fact, one of the major responsibilities of this neurotransmitter is to keep us awake. Other neurotransmitters which share the same responsibility include dopamine, norepinephrine, histamine and orexin.
At the same time, acetylcholine also helps us to have better sleep. This neurotransmitter supports REM sleep, which, in turn, helps the brain to take rest while storing memory.
Enhanced gut movement
Another major health benefit of acetylcholine is that is promotes gut movement. It is worth mentioning here that nicotine aids in gut flow via nicotine acetylcholine receptors. This is the main reason why some people (about 1 in 6) suffer from constipation when they give up smoking. In addition, antidepressant drugs also possess the ability to slow down this particular acetylcholine receptor and, hence, people taking these drugs often experience constipation as a side effect. In fact, the nervous system’s part that is responsible for parasympathetic (rest and digest) also makes use of acetylcholine to bring about such consequences.
The action of this neurotransmitter on other substances in our body sustains the process of secreting gastric juices into the intestines. Digestion takes place very efficiently in the presence of acetylcholine. This neurotransmitter also helps the body to take up the nutrients from the ingested foods effectively.
Acetylcholine also helps to reduce pain. During several studies, it was found that increasing the secretion oF acetylcholine or activating the choline receptors directly helped to reduce pain in mice as well as humans as the pain sensitivity increases when the choline receptors are blocked.
Presence of elevated levels of acetylcholine in our spinal cord relieves us from pain, while declining levels or activity of acetylcholine by blocking the receptors increases sensitivity to pain. Donepezil, a medication that enhances acetylcholine secretion, also provides relief from pain depending on its dosage in humans. This drug is also very effectual in treatment to prevent migraines.
During studies on animals, it was found that when the nicotinic receptors are activated it also provides relief from pain in acute cases and also in conditions of chronic pain.
Protection from infection
Among other things, acetylcholine also shields us from infections. Acetylcholine possesses the ability to adapt to inflammatory responses. In animal mode of infections, it has been established that this neurotransmitter can hold back formation of biofilm when one has fungal infections such as Candida albicans.
Improved blood circulation
Acetylcholine also helps to improve blood circulation. Presence of this neurotransmitter in the bloodstream enhances nitric oxide production in the blood vessels by muscarinic receptors, which results in enhanced blood circulation, by expanding the blood vessels, a process known as vasodilation.
Acetylcholine also influences the secretion of pituitary hormone by its effects on the hypothalamus of the brain. It results in the secretion of prolactin as well as the growth hormone from the pituitary glands.
Activating autonomic nervous system
This neurotransmitter also works to trigger the autonomic nervous system. Acetylcholine has a vital role in transmitting signals from one nerve to another nerve, particularly in the case of the autonomic nervous system. While bodily functions like heart contractions and breathing are said to be automatic, but even these crucial functions do not occur efficiently in the absence of acetylcholine or its action.
Supports muscular system
This neurotransmitter also promotes the muscular system vis-à-vis the locomotion of movement. The action of acetylcholine results in muscle fiber contraction and this, in turn, helps the body to be in motion – moving from one position to another.
Acetylcholine is also responsible for the constricting the pupils. Its role in the eyes is vital and necessary following an eye surgery. For instance, when an individual undergoes cataract surgery, this effect is necessary for the pupils to constrict. Acetylcholine helps to accomplish this.
Acetylcholine is regarded to be a very important substance in the body considering the various functions of this neurotransmitter and the range of health benefits it offers in the different systems of our body. This is the main reason why acetylcholine is used in several treatment modus operandi either as an ingredient or as a substance. For instance, the advantage of this neurotransmitter’s action on the nervous system is made use of during the treatment of Alzheimer’s disease.