Model studies for brain dialysis.

A dialysis cannula suitable for perfusing deep brain structures in animals is described and characterized in a series of model experiments. The effects of flow rate, concentration, variations in cannula construction, barriers to diffusion and pumping technique on the recovery of tryptophan from aqueous solutions at 37 degrees C were examined. The 200 micron diameter dialysis cannula gave good recoveries which varied from about 8% at 6 microliter/min to almost 90% at 0.15 microliter/min. Prepurification of the extracellular fluid by dialysis allows the sample loop of a high performance liquid chromatograph to be incorporated in the outflow line of the cannula for direct injection of dialysates.