Chronic cannulation of the intradural or extradural space in the rat

An animal preparation has been developed to test therapeutic agents in the extradural and intradural spaces. Under anaesthesia a hole was drilled in the penultimate lumbar vertebra of male Wistar rats and the appropriate space cannulated. The catheter was tunnelled subcutaneously to emerge at the neck. There was no spinal cord or meningeal reaction after 1 month. Catheters remained patent for 3 months. The method of cannulation allowed free rostral spread of drugs. Using plain 2% lignocaine, paralysis and anesthesia of the hind limbs required an intradural volume of 32 +/- 3 mulitre: the required volume on extradural injection was 46 +/- 2 mulitre (P less than 0.01). Paralysis of all limbs required an intradural volume of 115 +/- 12 mulitre. Respiratory arrest and death required a mean intradural volume of 179 +/- 15 mulitre.