Determination of half effective amount (ED50) of pentobarbital sodium
First, the purpose and principle of the experiment
The ED50 value of pentobarbital sodium (57-33-0) for the hypnotic effect of mice by intraperitoneal injection was determined. Sodium pentobarbital is a barbiturate sedative hypnotic drug. The hypnotic effect produced by intraperitoneal injection of mice at an appropriate dose is judged by the disappearance of righting reflexes. The indicator is only positive (sleep) and negative (not sleeping). Two phenomena are qualitative reactions. The abscissa of the mass response dose-effect curve is the logarithmic dose, and when the ordinate uses the frequency of the positive reaction, it is generally the normal distribution curve. If you use the cumulative positive frequency as the ordinate, you can get the standard S-shaped curve. The central portion of the curve (50% of the reaction) is close to a straight line with the largest slope, and the corresponding dose is the dose that causes an effect on half of the individuals in the population, commonly referred to as the half effect amount. If the effect is efficacy, the effective half (ED50) is called; if the effect is death, the median lethal dose (LD50) is called. These values ​​are important parameters for evaluating the strength of drug action and drug safety. 021-51602548
The design conditions of Sun's improved Kaerber method are as follows: The number of experimental animals in each group is equal, and the doses in each group are in equal proportions. The response rate of each group of animals is roughly consistent with the normal distribution.
If Xm is the logarithm of the maximum response rate group dose, i is the logarithm of the dose ratio between groups, p is the reaction rate of each group, Pm is the highest reaction rate, Pn is the lowest reaction rate, and n is the number of experimental groups, then: ED50= lg-1[Xm-i( ∑ P- 0.5) + i/4( 1- Pm- Pn) ] With 0% and 100% reaction rate, ED50= lg-1[Xm- i( ∑ P- 0.5) 95% confidence limit of ED50 = lg-1 ( lgED50 ± 1.96 · S) where S = i
Second, the experimental materials
50 mice, 1% sodium pentobarbital solution, cage, balance, 0.5 ml or 0.25 ml syringe.
Third, the experimental steps
1. Determine the dose to be administered: First, pre-test with a small number of animals to obtain the minimum dose (100%) of the mouse hypnotic reaction rate of pentobarbital sodium (ED100)
And the maximum dose (ED0) with a response rate of 0%. Then within this dose range, divided into several dose groups (typically 4 to 8 groups) according to the geometric ratio.
The ratio of the doses of each group (r) is r = n-1√ ED100/ED0
After r is obtained, the dose of the next adjacent group is obtained by multiplying the first dose group (ED0) by r. If divided into 5 groups, the doses of each group are ED0, r· ED0, r2· ED0, r3· ED0, r4· ED0, r5· ED0.
2. Administration: 50 healthy mice weighing about 25 g were randomly selected and randomly divided into 5 groups, 8 in each group (excluding 2 mice with extreme weight). The concentration of each group listed in Table 1 was intraperitoneally injected with 0.1 ml/10 g.
3. Recording results: The disappearance of the righting reflex was taken as the index of falling into sleep, and the hypnotic effect of the drug was observed. The number of sleeping rats within 15 minutes after intraperitoneal injection was recorded.
Fill in Table 1.
Fourth, the experimental results
Table 1 Table for calculating pentabarbital sodium ED50
According to the data in Table 1 and the above formula, ED50=31.90 can be obtained.
Precautions
1. To reduce the error, dispense by 1 person
2, keep the environment quiet
3. If there is a positive animal in the first group, add a low dose group down by the ratio (d0=d1/r)
4. The last group of animals are not all positive, and one dose is added upwards (dk+1=dkr)
Anesthesia methods for experimental animals, in addition to injection anesthesia with sodium pentobarbital, may also be anesthetized with isoflurane gas:
Small animal gas anesthesia machine
From: Yuyan Instrument Company
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