Laboratory Animals in Research

Laboratory Animals

• Rats, mice, rabbits, and guinea pigs are commonly used in laboratory experiments.
• Mice and rats are the most widely used animals due to their similarities with humans at anatomical, cellular, biochemical, and molecular levels.

Advantages of Using Rats and Mice

• Share similar brain functions with humans, such as anxiety, hunger, and memory.
• Relatively cheap and easy to maintain.
• Short generation time, reaching adulthood in approximately 3 months and having an average lifespan of 2 years.
• Easy to handle and accommodate.

Routes of Administration

• The route of administration depends on the property of the test substance and the objective of the experiment.
• Good handling is crucial for correct and successful administration.

Enteral Administration

• Has the advantage of allowing large amounts of nonsterile substances or solutions to be administered.
• May be affected by gastric juices and food content of the stomach.

Oral Administration (per os, p.o.)

• The simplest method of administration, but may not be practical for unpalatable, insoluble, or chemically unstable substances.
• May irritate the mucosa of the gastrointestinal tract.

Intragastric Administration

• Direct administration by oral gavage is preferred for precise measurement of substance intake.
• A ball tip needle is used to prevent damaging the oesophagus.

Parenteral Administration

• Includes injection, infusion, topical application, inhalation, and implantation of an osmotic pump.
• Small amounts of solution are injected, and large volumes are infused.

Subcutaneous Administration

• Easy to administer and rarely painful, making it suitable for conscious mice.
• Rate of absorption is lower than from intraperitoneal or intramuscular injections.
• Only used for nonirritating drugs.

Intraperitoneal Administration (i.p.)

• Technically simple and easy to administer.
• Rate of absorption is usually one-half to one-fourth as rapid as from intravenous administration.
• Limited by sensitivity to irritating substances and tolerance to solutions of non-physiological pH.

Intravenous Administration (i.v.)

• Has advantages over other routes, allowing for administration of high-concentration, high or low pH, or irritating solutions.
• Requires technical expertise and skill to avoid getting the solution outside the vein.
• Usually administered into the lateral tail veins, not the dorsal tail vein.

Intramuscular Administration (i.m.)

• Should be avoided in mice due to small muscle size.
• May be given into the thigh muscle with injection volumes, directing the needle tip away from the femur and sciatic nerve.
• Requires anesthesia or manual restraint.

Other Routes of Administration

• Intradermal administration
• Intra rectal administration
• Intranasal administration (i.n.)
• Topical application
• Inhalation
• Intracerebral administration
• Implantable pump