Acetylcholicin is a neurotransmitter that mediates binding functions in the human body. This compound delivers impulses to muscles and a whole range of organs. It is used in research, but its medicinal value is currently low due to significant side effects at high doses and the availability of more potent analogues.
General information
Acetylcholine has the formula CH3-CO2-CH2-CH2-N (CH3)3.
Acetylcholine is an organic compound that acts in the body as neurotransmitter, including in the parasympathetic nervous system and in the neuromuscular synapse. As a neurotransmitter, this compound has the following characteristics:
- its synthesis occurs in the presynaptic neuron;
- the accumulation of acetylcholine occurs in the vesicles;
- this compound is released in direct proportion to the strength of the stimulus causing this release (firing rate);
- the postsynoptic effect of this substance is directly illustrated by microinophoresis;
- this mediator can be deactivated using effective mechanisms.
It was determined that only compounds in which each of these characteristics is observed can be considered as mediators.
Chemically, acetylcholine is an ester formed by choline and acetic acid.
In the body, this substance is synthesized through cholinesterase, a special enzyme. When it breaks down, acetic acid and oxide are formed. The compound is unstable and, under the influence of acetylcholinesterase, it also degrades very quickly.
It is also possible to obtain it artificially in the form of one and from salts, for example, chloride. The drug obtained in this way (acetylcholine chloride) is used for research in the field of pharmacology and, in rare cases, as a drug. The compound is produced in the form of an ampoule with a volume of 5 milliliters, in which there is 0.1 or 0.2 grams of dry matter. For injection, it is dissolved in sterile water in a volume of 2–5 milliliters.
Acetylcholine is a white crystalline mass or colorless crystals.
Classification of choline proteins (which are and their specificity)
Choline proteins are subdivided into those affecting n-cholinergic receptors and m-cholinergic receptors. Choline receptors are complex protein macromolecules that are located on the outer side of the postsynaptic membrane.
The first of them are not sensitive, hence the letter "n" in their name. They are found within neuromuscular structures and ganglion synapses.
The second type of protein has acquired the letter "m" because they are muscarinic. They are present in the region of cholinergic postganglionic nerves. In other words, in the heart, smooth muscles and glands.
Synthesis of acetylcholine
In the nervous system, acetylcholine is synthesized with the participation of glucose. When it decays, acetyl groups appear, energy is released. Thanks to this energy, adenosine triphosphate arises, and already through this compound, the phosphorylation of intermediate compounds required for synthesis occurs. The penultimate stage is the formation of acetyl coenzyme A, from which acetylcholine itself appears following the reaction with choline.
At the same time, the mechanism of choline entering the place of formation of acetylcholine for the reaction with acetyl coenzyme A is currently unknown. It is assumed that half of it enters this place from the blood plasma, and another half remains after the hydrolysis of the previous
The synthesis of this substance occurs in the nerve endings inside the cytoplasm of the axons. After that, the compound is stored in synaptic vesicles (vesicles). In a separate similar organoid there are from 1000 to 10000 molecules of this compound. It is estimated that approximately 15–20% of the volume of a given substance in the vesicles is the amount of acetylcholine available for immediate use. The rest stored in the vesicles can only be activated for use some time after the corresponding signal.
The breakdown of acetylcholine in the human body occurs very quickly. This process is triggered by acetylcholinesterase, a special enzyme.
Functions
The function of acetylcholine is to serve as a mediator within the CNS (central nervous system). This substance affects the transmission of impulses from one section of the brain to another. At the same time, a small content of this substance contributes to the transmission of impulses, and a significant amount of it inhibits it.
Also, acetylcholine is used to transfer nerve impulse to the muscles of the body. With a lack of this substance, the force with which the muscles contract decreases. The lack of this particular compound leads to the fact that a person begins to suffer from Alzheimer's disease.
The action of acetylcholine is expressed in a slower heart rate, a decrease in blood pressure, and an increase in the diameter of peripheral blood vessels. The compound improves peristalsis in the digestive tract (intestines and stomach). Also, its presence enhances the contractile ability of the muscles of a number of organs, including the urinary and gall bladders, uterus, and bronchi. Acetylcholine enhances iron secretion, in particular in lacrimal, sweat, bronchial and digestive glands.
In addition, it causes constriction of the pupil (miosis), this effect becomes a consequence of more intense contraction of the control iris the sheath of the circular muscle, which is affected by the postganglionic cholinergic fibers located in the oculomotor nerve. This constriction of the pupil is most often combined with a decrease in intraocular pressure. This is due to the fact that with such a narrowing, the Schlemm's canal expands, as well as the space in the corner formed by the iris and the cornea. As a result, the fluid gets a great opportunity for outflow from the ocular internal environment.
Also, acetylcholine serves to improve concentration by the production of neurons located in basal nuclei.
Another function of connection is to influence falling asleep and waking up. The sleeper wakes up after the intensity of the activity of cholinergic neurons located in the brain stem, as well as in the forebrain in the basal nuclei, increases.
Acetylcholicin, produced artificially, is used for treatment only in a few cases. This is due to the fact that when taken orally, this compound is rapidly hydrolyzed, as a result of which its absorption from the mucous membranes of the gastrointestinal tract does not occur. When introduced into the body in a different way, including through injections, it also does not have a significant effect on the central nervous system. That is why now, in most cases, they refuse it.
It also needs to be borne in mind that acetylcholine constricts the veins in the heart. If an excessive dose of this substance is administered to a patient, the result may be bradycardia, a drop in blood pressure, arrhythmia, sweating, and other adverse effects.
