A METHOD TO PERFORM DIRECT TRANSCUTANEOUS INTRATHECAL INJECTION IN RATS

This work describes a method for performing direct intrathecal (i.t.) injections in rats without introducing a spinal catheter. Its ease of use in awake animals yields rapid and reproducible results with no sig n of motor impairment. The quality of each injection was ensured by th e observation of an injection-induced tail-flick. A 10-mu L injection of methylene blue was well localized yielding a very limited diffusion along the spinal cord. The method was validated by demonstrating that morphine (i.t.) had a marked antinociceptive effect and that naloxone (i.t.) blocked the effect of systemic (s.c.) morphine in mononeuropat hic rat.