What is dopamine?
Dopamine is one of the chemical factors of internal reinforcement (AFP), being an important element of the so-called “reward system”. The fact is that dopamine causes a feeling of pleasure or satisfaction, affecting motivation and learning. The substance can be actively developed in the body as a result of a positive (by subjective presentation) experience, for example:
- eating delicious food
- pleasant bodily sensations.
According to data from neurobiological experiments, the level of dopamine is able to increase, even when a person just remembers something pleasant. According to scientists, the main purpose of this neurotransmitter is to effectively fix in the memory of the actions important for survival and procreation.
This substance plays a significant role in the processes of ensuring cognitive activity, because the activation of dopaminergic transmission is necessary for the ability to switch attention. Due to the lack of this transmission, increased inertness may develop in patients.Clinically, it most often manifests itself in the form of bradifrenia (delayed cognitive processes) and perseverations (stable repetition of certain actions, phrases, or emotions). Such violations are one of the most characteristic manifestations of diseases with dopaminergic insufficiency, in particular, Parkinson's disease.
Dopamine in the "reward system"
In the middle of the last century, Canadian scientists James Olds and Peter Milner concluded that there was a certain pleasure center in the brain, where dopamine was the main method of transmitting nerve impulses. As a result, researchers have put forward a version that this substance may be associated with a sense of pleasure. Later, this theory was confirmed by radionuclide tomographic scanners and the discovery of drugs that effectively suppressed the productive symptoms of schizophrenia (antipsychotics).
Like many other neurotransmitters, dopamine has synthetic analogues, as well as stimulants that contribute to an increased release of this substance. In particular, the production and release of dopamine can significantly increase the narcotic substances.As a result, drug users artificially form a sense of pleasure.
Some prohibited substances are able to directly stimulate the release of dopamine, affecting the transport process, while others are blocking the natural mechanisms of dopamine reuptake. As a result, the concentration of dopamine increases in the synaptic space.
Speaking about the most common harmful addictions, it should be noted that nicotine mimics the action of natural neurotransmitters, and the use of alcohol can block the action of dopamine antagonists.
When people long enough and too often try to “deceive” their own “reward system” by stimulating it with cigarettes, alcohol or prohibited substances, the brain gradually gets used to it. Adapting to the artificially elevated dopamine level, it begins to adapt, producing less hormone, while lowering the number of receptors in the “reward system”. As a result, there is a need to increase the dose of substances that can enter a person into a state of satisfaction, as this can often happen with drug addicts.
In the future, the development of chemical tolerance can provoke the formation of metabolic disorders in the brain, and then cause significant damage to brain health.
Dopamine use in medicine
Dopamine is also called the drug, which is produced in the form of a concentrate for preparing a solution for infusion. In the production of this tool, in addition to the active substance - dopamine hydrochloride (in 1 ml of its solution contains 5, 10, 20 or 40 mg), additional components are also used:
- sodium disulfite,
- hydrochloric acid 0.1M solution,
- water for injections.
The drug is available in 5 ml ampoules.
Indications for taking dopamine are:
- shock of various genesis, including cardiogenic, postoperative, infectious-toxic, anaphylactic, hypovolemic (the drug is used only after the recovery of circulating blood volume);
- various genesis acute cardiovascular insufficiency;
- low cardiac output syndrome (in cardiac surgery patients);
- arterial hypotension.
In addition, the drug is effective in increasing diuresis in case of poisoning.
The pharmacological action of dopamine, which is an agonist of dopamine receptors, is due to its cardiotonic and hypertensive effect of the drug. In small doses, dopamine affects dopamine receptors. By expanding the renal, mesenteric, coronary and cerebral vessels, it affects peripheral dopamine receptors.
When prescribing low and medium doses (from 2 to 10 mcg / kg / min), dopamine manifests itself as a means of stimulating postsynaptic β1-adrenoreceptors. Due to the positive inotropic effect and an increase in the minute volume of blood, the coronary blood flow and the level of myocardial oxygen saturation usually increase. Often, this may increase systolic blood pressure (BP) and pulse, while diastolic blood pressure and the level of total peripheral vascular resistance (OPSS) most often remain unchanged.
The use of high doses of dopamine (10 µg / kg / min or more) due to stimulation of α1-adrenoreceptors causes an increase in OPS, heart rate and narrowing of the renal vessels, as a result of which the previously increased volumes of renal blood flow and diuresis can decrease.Increased minute blood volume and OPSS causes an increase in both systolic and diastolic blood pressure.
The drug begins to have a therapeutic effect within five minutes (with the introduction of a vein). The effect of dopamine lasts for about ten minutes.
How dopamine is used
The dosage is set strictly individually, taking into account the severity of shock, blood pressure and the patient's response to the introduction of dopamine. Usually, a drug administered in order to increase myocardial contractility and increase diuresis is administered intravenously at a dosage of from 100 to 250 μg / min. When dopamine is used to affect blood pressure, the dosage can be increased to 700 µg / min.
The drug is administered drip. Dopamine is used for up to 28 days. The maximum dose for adult patients is 1.5 mg / min. Dopamine is administered under the control of heart rate, blood pressure, ECG, and diuresis, a decrease which indicates the need to reduce the dosage of the drug.
In some cases it is also necessary to monitor the stroke volume of the heart, the level of filling of the ventricles, the central venous pressure and the pressure in the pulmonary artery.
Often, patients may experience undesirable effects, in particular:
- tachycardia or bradycardia;
- pain in the chest;
- changes in blood pressure;
- ventricular or supraventricular arrhythmias (when prescribing the drug in high dosages).
Patients may also complain of nausea, vomiting, bleeding of the gastrointestinal tract, headaches, tremor of the fingers, increased anxiety, polyuria.
Given the method of administration of the drug, when a substance enters the skin, local reactions such as necrosis of the skin and subcutaneous tissue may occur.
Dopamine is not used if patients have previously been diagnosed:
- hypertrophic obstructive cardiomyopathy;
- ventricular fibrillation;
- hypersensitivity to dopamine.
During periods of pregnancy and lactation, the drug is prescribed only in cases where the intended therapeutic effect for a woman far exceeds the likely risk to the fetus or child.
Dopamine is used with caution in children and adolescents under the age of 18 years. In appointing the drug is usually used dosage of 4-6 mg / kg / min.
Date: 09.10.2018, 12:37 / Views: 53331
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