Antitussive effect of codeine
1. Cough reflex Cough is a defensive respiratory reflex that removes airway obstruction or foreign bodies.
The cough reflex arc consists of four links:
Receptors (respiratory tract) Afferent nerves (mainly vagus nerve) Efferent nerve effectors from the cough center nerve.
1. Mechanical stimulation
2. Electrical stimulation
3. Chemical stimulation
(1) Aerosol inhalation: suitable for sober animals
(2) Direct injection: suitable for anesthetized animals
2. Big and small mice,
It is cheap and easy to obtain, and it is sensitive to chemical stimuli, but it has a large variation and is unstable, and the coughing sound is small and it is not easy to observe.
3. Guinea pigs are very sensitive to various stimuli, easy to induce cough, loud cough sound, easy to observe, so it is a common animal for the initial screening of antitussive drugs.
4. Cats are relatively expensive, sensitive to various stimuli, and rarely cough under normal physiological conditions. They are often used to further confirm the efficacy of the drug.
5. Dogs are expensive, sensitive to various stimuli, and cause little variation in cough, and the indicators are relatively stable, so it is suitable for observing the duration of antitussive effects of drugs.
6. Rabbits are not sensitive to irritation and are not likely to cause cough, and are rarely used to screen antitussive drugs.
4. Antitussive drugs Antitussive drugs are divided into central antitussive drugs and peripheral antitussive drugs.
Codeine: It is an opioid alkaloid, which can suppress the cough center of Yannao cough, the therapeutic dose does not inhibit breathing, and has little addiction and fewer side effects. Because it suppresses cough reflex, sputum is not easy to discharge, so it is only suitable for non-sputum dry cough.
V. Specific experiments
After inhaling the irritating chemical aerosol, the mice stimulated the respiratory tract receptors, causing reflex to cause coughing.
1. Learn how to induce cough with concentrated ammonia;
2. Observe the antitussive effect of codeine;
3. Significance test (t-test) of learning volume response data.
1. Animal: Kunming mouse, weighing 18-22g, â™€â™‚
2. Equipment: squirrel cage, balance, applicator, cotton ball, large beaker
3. Medicines: 0.3% codeine phosphate, 0.9% saline, concentrated ammonia
1. Take 8 mice from each group, weigh them, mark them, and randomly divide them into two groups;
2. Administration: the experimental group ig codeine 0.2ml / l0g, the control group ig saline 0.2ml / l0g, each mouse administration interval is about 4min; Note: phosphate codeine suspension should be mixed after Then ig, to ensure uniform administration.
3. Tuck the mouse into a 500ml beaker 30 minutes after administration, and then quickly put a cotton ball infused with 0.2ml concentrated ammonia into the beaker, immediately record the cough latency of the mouse and the number of coughs within 2 minutes. Note: â‘´ The size and tightness of the 8 cotton balls must be moderate and as consistent as possible; â‘µ The incubation period is the time from the time the cotton ball is put into the first cough; To contract the abdominal muscles violently and open the mouth.
Summarize the results and do a t-test of the number of coughs.
Volume response data: Pharmacological effects can be measured by changes in dosage, such as blood pressure, height, weight, and red blood cell count.
The index of this experiment is the number of coughs, which is a specific value, a quantitative response data, and t-test is used for statistical analysis.
Steps of t-test:
â‘´ Establish hypothesis;
â‘µ Calculate the value of t (see formula P32 for the formula);
(3) Determine the degree of freedom and check the t value table;
â‘· Judgment result
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