Animal experiments

• Q1: What are the methods for labeling and numbering experimental mice?

  A:: 1. Dyeing method: marking and distinguishing experimental animals by dyeing parts and colors; 2. Ear hole method: distinguishing experimental animals according to the part and number of holes punched in the animal's ears, which can be marked with three digits number within; 3. Branding method: causing slight damage; 4. Tag method: branding the compiled number on a metal plate and hanging it on the neck, ears, limbs or cage of the experimental animal; 5. Cage numbering Method; 6. Toe numbering method, tail numbering method, coat numbering method, etc.

• Q2: What is the normal weight range of C57BL/6N mice?

  A:

  male
  Weight(g)	Age (days)
  <12	<23
  13-15	24-28
  16-18	29-35
  19-21	36-45
  22-24	45-63

  female
  weight	Age (days)
  <12	<23
  13-15	24-31
  16-18	32-52
  19-21	53-77
  22-24	78-105

• Q3: What are the common anesthesia methods for rats?

  A：

  (1) Intraperitoneal anesthesia: Mix isoflurane and fat emulsion to make emulsified isoflurane, inject it intraperitoneally, anesthetize for 3 minutes, and wake up after 30 minutes.

  (2) Inhalation anesthesia. Seal the rat into a sealed cylinder and inject liquid inhalation anesthetic.

  (3) Under intraperitoneal anesthesia via orotracheal intubation, the limbs are fixed on their backs, and the upper and lower incisors are tied with silk threads for traction. The operator wears a forehead mirror, places a light source on the opposite side, pulls out the tongue and the lower incisor silk threads and holds them together with the left hand. The upper incisor silk thread is carried by an assistant or clamped with a hemostatic forceps and fixed with your own chest. Pull the silk thread to lift the head and fully open the mouth. Hold an 18G or 16G trocar in your right hand and insert it when you see the glottis. Tube.

• Q4: What are the key points that need to be paid attention to when administering intragastric administration to mice?

  A：

  (1) The mouse needs to be fixed, the head and body should be kept in a straight line, and the mouse should be in an upright position with the head upward during gastric administration;

  (2) The dose of intragastric administration can be 0.1 mL/10 g or 0.2 mL/10 g, depending on the actual situation to prevent mice from lying prone and wheezing after intragastric administration;

  (3) Before the operation, place the intragastric needle on the syringe and roughly measure the length from the mouth to the position in the stomach (the posterior edge of the last rib). Determine the insertion depth based on this distance. For adult mice, the insertion depth is approximately 3 cm;

  (4) Insert the needle from the corner of the mouse's mouth. After entering, let the gastric gavage needle follow the upper palate of the mouse and press its tongue into the esophagus. There will be a breakthrough feeling. There will be no obvious resistance after the breakthrough feeling and during the infusion of liquid;

  (5) Adult mice can be fed a maximum of 1.0 mL each time.

• Q5: What are the vaccination routes and methods for animal experiments?

  A：

  (1) Intradermal vaccination: usually the skin of the back is suitable.

  (2) Subcutaneous vaccination: Choose the abdominal wall, back or groin.

  (3) Intramuscular vaccination: Generally, buttocks and thigh muscles are used, and for poultry, chest muscles are suitable.

  (4) Intravenous inoculation: The outer edge of the ear vein is suitable for rabbits, the tail vein for mice and rats, the hind leg vein for guinea pigs, and the subwing vein for chickens.

  (5) Intraperitoneal vaccination: commonly used in mice.

  (6) Intracerebral inoculation: commonly used in mice. Rabbits and guinea pigs need to use a steel cone to make holes before injecting because their skulls are hard.

  (7) Soles (pads) vaccination.

• Q6: How to identify the age of rats and mice through morphology?
  A: The naked body of the 1-day-old rat is bright red, the ear shell is exposed at the 3-day-old, the scar is expected to fall off at the 4-day-old, the rat can turn over at the 5-day-old, crawls at the 8-day-old, can hear sounds at the 10-day-old, and the whole body is 9-11 days old. They are covered with white fur and have incisors. At 13-15 days of age, their eyelids open and they can jump and grab things. After 18 days of age, they can feed themselves and live independently.
• Q7: How to determine age based on weight?

  A：

  Mouse age/d	newborn	5	10	15	20	25	30
  Mouse weight/g	1.8	4.0	6.0	11.0	15.0	21.0	21.0
  Rat age/d	newborn	10	20	30	40	50	60
  Rat body weight/g	6-7	17-25	35-50	55-90	100-150	150-210	170-240

• Q8: How to improve the success rate of tail vein injection?

  A：

  (1) Before injection, soak the tail of the mouse in hot water at about 50°C for about 1 minute until the tail vein is obviously filled;

  (2) Flatten and tighten the tail so that the tail vein is on a flat surface; if this is not possible, you can use your hands to hold up or stand on tiptoe to stretch part of the tail to stretch the tail vein;

  (3) Apply alcohol to the tail before injection to completely expose the tail vein;

  (4) When injecting, the bevel should be upward. Choose a direction parallel to the tail vein to insert without any angle. Insert the needle about 0.5-1cm and withdraw the needle but do not withdraw completely. When the bevel withdraws about half way, there will be blood if the needle is in the blood vessel. Come out, and then insert the needle again. The needle insertion distance should be shorter than the first needle insertion distance, otherwise the blood vessel will be punctured! Then inject the liquid. At this time, you should not feel much resistance. You can see that the tail vein blood vessels turn white, but the surrounding tissue is not swollen. At this time, the tail vein injection is successfully completed;

  （5）It is not recommended to feel whether the injection has entered the blood vessel based on the bolus pressure, because this will waste some cells and lead to inaccurate counting.