EXPERIMENTAL TECHNIQUES (cont)
Intramuscular injections in the guinea pig must be made into the large muscles of the thigh. The syringe must be aspirated after the needle is inserted to assure that it is not in a blood vessel. Blood will enter the syringe if the needle is in a vessel. If this happens, the needle should be slightly repositioned and checked again by aspiration.
Certain anesthetics may cause sciatic nerve damage when injected into the posterior thigh. This damage may result in self mutilation of the rear foot. Therefore, use the anterior thigh muscle rather than the posterior when giving injections of these agents.