A 26 gauge needle or smaller is used for venipuncture in mice and a 20 gauge needle or smaller in rats. Injection of tail veins is generally accomplished by compression of the lateral tail vein by applying pressure at the base of the tail. In rabbits, ear veins, tarsal veins or cephalic veins are common sites for intravenous injection. Ear veins are also a useful site in guinea pigs. Intradermal and intraarterial injections are discouraged and require justification from the investigator.
Intrathecal injections require general anesthesia.