Cannulae implantation and IV catheterization were performed according to Hansen et al., (2007) and Mark et al., (2006). Briefly, animals were anesthetized with an intraperitoneal injection (0.1 cc/kg) of an anesthetic mixture containing the following: 55.5 mg/cc ketamine, 5.5 mg/cc xylazine, and 1.1 mg/cc acepromazine. The anesthetized animal was then secured in a Cartesian stereotaxic apparatus (Kopf Instrument, Tujunga, CA) using ear bars. Skulls of animals were exposed and bilateral burr holes (5 holes) were drilled to the dura mater in the following skull coordinates of Paxinos and Watson (1998): A- 8.5, L± 1.2, V- 4.0. These skull coordinates allowed microinjectors to reach the LDTg 3.5 mm below the end of the implanted guide cannulae. These coordinates targeted a large portion of the LDTg and especially the medial subdivision of the LDTg, which is thought to contain a large portion 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
