Acetylcholine

The acetylcholine was prepared synthetically in 1867 and can be easily obtained the hill heating with acetic anhydride . It is preserved for a long time in an acid medium (pH 3.9) but its hydrolysis is very rapid in an alkaline medium and releases acetate and choline.

Definition

Acetylcholine is a neurotransmitter , that is, this substance transmits information from one neuron to another . It is stored in vesicles at the tip of a first neuron and is secreted during an electrical influx at the synapse (space between two neurons). Acetylcholine then binds with receptors on the limb of the second neuron to propagate this influx before being taken up again by the limb of origin. In this way the electrical influence spreads in the nervous system.

What is it for

Acetylcholine is a neurotransmitter that serves to convey the nervous message . The latter must pass from one neuron to another to move. The inter-neuronal space is called synapse and it is there where acetylcholine intervenes.

This substance is stored in the vesicles at the end of a neuron . At the moment of passing the nervous message, acetylcholine is released and transports it to the next neuron in the synapse. Then it returns to the interior of the vesicles where it is stored.

Function

As a neurotransmitter, acetylcholine plays an essential role in the formation of memories, the capacity for concentration and logical rationing . Provides protective benefits and can limit neurological deterioration. Indeed, with aging, acetylcholine levels tend to decrease and this decrease seems to play a fundamental role in the episodic short-term memory gaps that are generally associated with older people.

This happens because acetylcholine controls how fast electricity circulates in the body . This directly affects the way of thinking, attention and in which information is retained in memory . Indeed, if there is some kind of deficiency, the person may become more distracted and less fast mentally and physically. A basic function of acetylcholine is to lubricate and isolate muscles, bones, and all internal organs in the form of fat. Thus, an acetylcholine deficiency would also have a dehydrating effect on the body.

In addition, acetylcholine can intervene in the ingestion of food and in the digestive process. It can influence the increase in blood flow in the intestinal tract.

Presentation

Acetylcholine is a small organic molecule . Its crude formula is C7 H16 O2 N1. Its molar mass is 146.2 g / mol. It has an ester function and a quartenary ammonium function . The structure of a molecule such as acetylcholine can be determined by methods such as spectroscopy, that is, the study of the interaction between matter and infrared rays, which has the effect of vibrating chemical associations.

Acetylcholine, one of the most important compounds in the human body, is a very simple molecule . Other neurotransmitters , like glycine, are even simpler. Likewise, there are other more complex ones, with the presence of aromatic rings. This is the case with serotonin.

The study of this neurotransmitter was simpler than that of others. This is explained by the fact that the synapses that release acetylcholine are much less buried in the central nervous system than other synapses that use another neuromediator.

Dose

In the case of intraocular ophthalmic surgery, the usual dose is usually 0.5 to 2 ml. In the case of Alzheimer’s patients, it will depend on the degree of the disease.

Acetylcholine effects

Effects on the central nervous system

Neurons, especially those related to the processes of sleep, wakefulness and attention; they release acetylcholine in the central nervous system. In that sense, acetylcholine allows learning, memorization and memories . That is why people with Alzheimer’s disease have a significant lack of acetylcholine in various regions of the brain.

Effects on the peripheral nervous system

In this case, acetylcholine is responsible for making muscle activity possible . This transmits the nervous influx to the muscles. Synthesized in the cytoplasm of the neurons that send the information, the presynaptic neurons, this allows the control of the muscles through the nerves at the moment of flexion and extension.

Effects on the autonomic nervous system

At this level, it  intervenes in inter-neuronal transmission . The presynaptic fiber releases acetylcholine which, by opening the sodium channels linked to the nicotinic receptors and leads to depolarization due to a new influx in the postsynaptic fiber. This stimulation in turn causes a release of acetylcholine from the parasympathetic endings and of catecholamines from the adrenergic endings.

Synthesis

Acetylcholine is synthesized from choline, a fundamental nutrient generated by the human body . Choline is stored in cholinergic neurons through a reaction with actyl CoA and under the enzymatic influence of choline acetyltransferase.

Choline is a molecule present in the extracellular environment of the central nervous system and in synapses. It comes from food and a permanent synthesis by the liver, where it is produced in the form of phosphatidylcholine. These larger molecules constitute, to a large extent, the membrane of the axons of neurons. It is estimated that they represent a third of the dry weight of the brain, as well as 15% of the weight of the nerves. Acetylcholine appears to be the product of a simple esterification reaction between acetic acid and choline.

To summarize, the synthesis of acetylcholine is carried out within the neuron, particularly, in the nucleus of the cell . When it has already been synthesized, the substance leaves the nucleus of the neuron and passes through the axon and dendrites, which are in charge of communicating and associating neurons.

Receivers

The receptors are subject to the action of acetylcholine antagonists or agonists. Acetylcholine receptors are found on the postsynaptic membrane of neurons in the central nervous system and in muscle cell or vegetative ganglia. These are channels that let Na + and K + pass through. When acetylcholine is absent, these channels close in a resting state

The main acetylcholine receptors are of two types: nicotinic and muscarinic . These two types of receptors are classified as metabotropic. This means that they are capable of being activated and that this activation modifies their conformation and leads to a series of intracellular events.

Nicotinic receptors

It is well known that the main addictive component of tobacco is nicotine. This alkaloid is active in man since it mimics the action of acetylcholine, an endogenous molecule, and interferes with physiological processes. Nicotine acts as an agonist on one of the two types of acetylcholine receptor and it is for this reason that they are called nicotinic acetylcholine receptors . These receptors belong to the family of ion channels activated by ligands involved in rapid responses to neurotransmitters.

Muscarinic receptors

These are located in effector cells that are stimulated by post-ganglionic cholinergic nerve fibers. To give an example of the function of these receptors, we can mention the sweat glands in certain vessels contained in the voluntary muscles of the body. In muscarinic receptors, acetylcholine inhibits or excites depending on the organ studied .

Inhibitors

Acetylcholinesterase inhibitors can be found in poisons in nature . That is why these can be used as various types of weapons. In the medical field , they can be used to treat myasthenia, Alzheimer’s and as an antidote to counteract anticholigernic poisoning.

Enzymes that normally complex with their substrate can be subjected to the action of inhibitors that slow down or even completely abolish the reaction with the substrate.

What foods contain acetylcholine?

Foods rich in acetylcholine are important for improving muscle contraction, attention, and the ability to store information. Indeed, acetylcholine promotes communication between brain cells. In that sense, these foods are ideal for those who want to improve their memory.

Some foods that are a rich source of acetylcholine are:

• Eggs.
• Dairy like milk and cheese.
• Yeast.
• Sunflower seeds.
• Mushrooms.
• Salmon.

The above foods increase acetylcholine in the body as they contain choline and vitamin B5, which are substances used by the body to produce acetylcholine.

Tradename

Acetylcholine is commonly known as Miochol-E , a drug made from acetylcholine chloride and frequently used in ophthalmic surgeries.