A small-gauge cannula device for continuous infusion of exogenous agents into the brain

A method is described for the construction of an intraventricular or intraparenchymal cannula device, which when connected to an Alzet osmotic pump, can be used for the continuous infusion of experimental solutions into the brain. A 33-gauge, stainless-steel cannula is encased within a dental acrylic stabilization platform prior to stereotaxic implantation, and after implantation, the platform is glued to the animal's skull using cyanoacrylate adhesive. This procedure provides for the long-term stability (at least 4 weeks) of the small-gauge cannula without the need for additional stabilization skull screws, thus minimizing damage to surrounding tissues by the cannula and postsurgical trauma to the animal. Using the stock model 2002 Alzet pump to infuse artificial cerebral spinal fluid at a flow rate equal to 0.5 microliter/h, an inflammatory tissue reaction around the cannula tip was consistently found after 2 weeks of continuous intraparenchymal infusion. However, the inflammatory reaction could be significantly reduced or eliminated by decreasing the flow rate to approximately 0.25 microliter/h, using a modified Alzet pump. Alternatively, the stock 0.5 microliter/h pump could be used without causing parenchymal damage if the cannula tip was implanted into the lateral ventricle.