Figure 7.2.1.

Diagram of side-by-side microdialysis probe described in Alternate Protocol 1 (Design 2) for in vivo preparations in which the microdialysis probe is inserted through a guide cannula in the rat. (A) Two pieces of fused silica tubing are threaded through a connector that is fitted with a short piece of Silastic tubing attached to the inlet tubing and a guide cannula of the appropriate length. The lengths of fused silica tubing exiting the cannula are adjusted so that the tips of the outflow and inflow tubing are separated by the distance that defines the active area of the membrane. Further, the two pieces of silica are placed so that the tip of the outflow tubing is flush with the end of the guide cannula. (B) Enlarged view: Once the silica is properly positioned, superglue is applied to the Silastic tubing to permanently fix the silica in place. The guide cannula is then removed and saved for later implantation into the rat. The final step in constructing the dialysis end of the probe (refer to panel A) involves slipping a tube of dialysis membrane over the end of the two pieces of silica until the sealed end of the dialysis tubing is flush with the inflow silica tubing. The membrane is then attached to the silica with polyimide sealing resin, and all areas of the membrane not intended to support dialysis are sealed with a thin coating of the resin. To complete the probe for in vivo use, the length of silica tubing that runs from the connector to the pump is covered with Teflon tubing, and the junction of the connector, Silastic tubing, and Teflon tubing are stabilized by covering the area with a small tube (e.g., made from a cut-off syringe cap) and filling with fast-drying epoxy. Adapted from Wages et al., 1986.