Self-administered meth and object-in-place recogni-tion memory. Sixteen standard self-administration chambers(30 × 20 × 20 cm, Med Associates) were housed inside sound-attenuating cubicles fitted with a fan for airflow and maskingnoise. Each chamber contained two retractable levers, two stimu-lus lights, a speaker for tone delivery, and a house light to providegeneral illumination. In addition, each chamber was equippedwith a balanced metal arm and spring leash attached to a swivel(Instech). Tygon tubing extended through the leash and was con-nected to a 10 ml syringe mounted on an infusion pump locatedoutside the sound-attenuating cubicle.For rats that underwent surgery, anesthesia consisted of IPinjections of ketamine (66 mg/kg; Vedco Inc, St Joseph, MO, USA),xylazine (1.3 mg/kg; Lloyd Laboratories, Shenandoah, IA, USA),and equithesin (0.5 ml/kg; sodium pentobarbital 4 mg/kg, chloralhydrate 17 mg/kg, and 21.3 mg/kg magnesium sulfate heptahy-drate dissolved in 44% propylene glycol, 10% ethanol solution).Ketorolac (2.0 mg/kg, IP; Sigma, St. Louis, MO, USA) was given justprior to surgery as an analgesic. One end of a silastic catheter was inserted 33 mm into the external right jugular and secured with 4.0silk sutures.
The other end ran subcutaneously and exited from asmall incision just below the scapula. This end attached to an infu-sion harness (Instech Solomon, Plymouth Meeting, PA, USA) thatprovided access to an external port for IV drug delivery. An antibi-otic solution of cefazolin (10 mg/0.1 ml; Schein Pharmaceuticals,Florham Park, NJ, USA) was given post surgery and during recoveryalong with 0.1 ml 70 U/ml heparinized saline (Elkins-Sinn, CherryHill, NJ, USA).