An experiment is the main method of pathophysiology, which involves the study of a disease in laboratory animals that are the object of modeling human diseases. 

An experiment in the broadest sense is an active human influence on nature and artificial reproduction of its various phenomena in order to learn objective laws. An experiment is the basis of an empirical approach to knowledge; it is a scientific research method that is repeated an unlimited number of times under the described conditions and gives identical results; the possibility of setting up an experiment is the main difference between a scientific theory and a pseudoscientific one; important characteristics of an experiment are its reliability and validity.

The planning stage includes the following items:

a) creation of a working hypothesis;

b) setting the goal and objectives of the study;

c) determination of the object of the experiment (species, age, sex of animals);

d) drawing up an experiment scheme (nature and frequency of pathogenic effects, dose, duration, etc;)

e) determination of the scope of research (number of experimental animals and research groups, list of specific methods to be used).

The stage of disease modeling involves the experimental reproduction of diseases and pathological processes. The main methods of disease modeling:

- method of removal (removal of the liver to model liver failure, pancreas to model diabetes, etc;)

- method of destruction or damage - surgical interventions are used (nerve crossing, destruction of nerve centers, tissue damage, etc.), physical factors (temperature, ionizing radiation, etc.), chemicals (poisons, inhibitors), immune effects (antibodies, anti-tissue sera)

- overload method (modeling neuroses by causing functional overloads of higher CNS centers, heart failure by creating artificial heart defects, etc;)

- a method of creating deficits (modeling hypoxia by limiting the amount of oxygen in a barocamp, hypo- and avitaminosis by using diets that do not contain vitamins, etc;)

- the method of disruption of nervous and humoral regulation (carried out by irritation or damage to nervous structures, pharmacological interventions in the metabolism of neurotransmitters, the introduction of large amounts of hormones, etc;)

- method of creating obstacles (ligation of a vessel to model myocardial infarction and arterial hypertension, common bile duct - mechanical jaundice, etc;)

- exogenous induction method (modeling of infectious diseases, malignant tumors, allergies by introducing into the body or exposing it to factors that are specific pathogens);

- transplantation method (in the study of tumor growth, atherosclerosis, allergic reactions); 

- explantation method - study of pathological processes outside the body: in tissue cultures, on isolated organs (in the study of tumor growth, atherosclerosis, allergic reactions);

- transgenic technologies - breeding animal lines with predetermined genetic defects that lead to disease development (for the study of hereditary diseases, atherosclerosis and arterial hypertension, malignant tumors, endocrine diseases, inflammation).

The stage of obtaining scientific facts. When modeling a disease, researchers try to obtain as much information as possible about changes in the body of experimental animals during the dynamics of the pathological process and at the end of it (after the animal is slaughtered). For this purpose, various methods are used, namely

- morphological (macroscopic examination, light and electron microscopy, etc.)

- functional (recording of muscle contractions, electrocardiography, encephalography, recording of spirograms, determination of oxygen consumption, etc;)

- biochemical (determination of the concentration of substrates, hormones, electrolytes, metabolic products, enzyme activity);

- immunological (determination of the type of antibodies, lymphocyte blast transformation, etc.)

- Comparative methods. Depending on the objects of comparison, the following methods of analysis are distinguished:

a) phylogenetic - modeling and comparison of pathological processes in animal species at different stages of evolutionary development;

b) ontogenetic - at different stages of individual development of animals;

c) topographic and anatomical - comparing different organs, different parts of the same organ, different types of tissues and cells.

- The method of combining pathogenic influences, which involves the use of various combinations of pathogenic factors, allows to identify such properties of the pathological process that remain hidden if only one factor acts on the body.

- The method of corrective actions involves first modeling the pathological process, and then attempts to eliminate certain manifestations of the pathological process by introducing certain substances or other effects (to find means of treatment and prevention).

Reference:

Атаман О. В. Патофізіологія / О. В. Атаман. – 2-ге вид. – Вінниця : Нова Кн., 2016. – Т. 1 : Загальна патологія. – 580 с.