Brain dialysis: detection of acetylcholine in the striatum of unrestrained and unanesthetized rats

A dialysis cannula was implanted into rat striatum while the animals were anesthetized, and after at least one day following the surgery the area was perfused with Ringer solution under the unrestrained and unanesthetized conditions. Concentration of acetylcholine (ACh) in the perfusate was determined by high-performance liquid chromatography (HPLC)-electrochemical detection (ECD) with the enzyme-column on which acetylcholine esterase and choline oxidase were immobilized. ACh in the dialysate was only detectable when the Ringer solution containing eserine, an inhibitor of acetylcholinesterase, was perfused. ACh peak on HPLC-ECD could be detected at least for 4 h under these conditions. The level of ACh increased 2-3 fold with the perfusion of 1 mM atropine sulfate, a blocker of ACh receptor. These data indicate that brain dialysis in the presence of eserine is useful for study on the neurochemical activity of ACh neurons in the brain.