CHRONIC CANNULATION OF THE INTRADURAL OR EXTRADURAL SPACE IN THE RAT

An animal preparation has been developed to test therapeuticagents in the extradural and intradural spaces. Under anaesthesiaa hole was drilled in the penultimate lumbar vertebra of maleWistar rats and the appropriate space cannulated. The catheterwas tunnelled subcutaneously to emerge at the neck. There wasno spinal cord or meningeal reaction after 1 month. Cathetersremained patent for 3 months. The method of cannulation allowedfree rostral spread of drugs. Using plain 2% lignocaine, paralysisand anaesthesia of the hind limbs required an intradural volumeof 32±3 µlitre: the required volume on extraduralinjection was 46±2µlitre (P<0.01). Paralysisof all limbs required an intradural volume of 115 ±12µlitre.Respiratory arrest and death required a mean intradural volumeof 179±15µlitre. Present address, for correspondence: Department of Anaesthetics,University Hospital of Wales, Health Park, Cardiff CF4 4XW