of the cholinergic neurons (Wang and Morales, 2009). To ensure penetration of the guide cannulae, the dura mater was punctured with a needle bilaterally through the two burr holes. To anchor the guide cannulae and a U-shaped aluminum shield to the skull, three 5-mm stainless steel screws (size 0-80) were screwed into the remaining burr holes prior to applying dental acrylic. Head shields were used as an attachment point for a tether, which prevented animals from disturbing the infusion line that connected to the IV catheter. The bilateral guide cannulae were 10-mm, 21-gauge stainless steel guide shafts that had a small stainless steel fiber soldered approximately 2 mm below one end.
