Model env 203 1000

Monkeys were housed individually in well-ventilated, stainless steel chambers that also served as experimental chambers. Each chamber was equipped with a custom operant panel mounted on the front wall. Three square translucent response keys were arranged in a horizontal row, and only the left and right keys were used in the present study. Each chamber was also equipped with a pellet dispenser (Model ENV-203-1000; Med Associates, St Albans, VT) and two syringe pumps (Model PHM-108; Med Associates), one for each lumen of the double lumen catheter. One syringe pump (the “self-administration” pump) delivered response-contingent cocaine injections. The second syringe pump (the “treatment” pump) delivered noncontingent saline, d-amphetamine, or risperidone injections through the second lumen of the catheter at a programmed rate of 0.1-ml infusions every 20 min from 1200 to 1100. The intravenous catheter was protected by a tether and jacket system (Lomir Biomedical, Malone, NY) that allowed the monkeys to move freely. Catheter patency was periodically evaluated by intravenous (i.v.) ketamine (3 mg/kg) administration through the catheter lumen, and after any treatment that decreased cocaine vs food choice. The catheter was considered patent if ketamine produced a loss of muscle tone within 10 s.

The housing chamber served as the experimental chamber and was equipped with a custom operant panel, a pellet dispenser (Med Associates, Model ENV-203-1000, St. Albans, VT), and two syringe pumps (Model PHM-108, Med Associates). One “self-administration” pump delivered contingent methamphetamine injections through one catheter lumen. The second “treatment” pump delivered a 0.1 mL noncontingent saline infusion through the second catheter lumen at a programmed rate of every 20 minutes from 1200 each day until 1100 the following morning. The intravenous catheter was protected by a customized stainless steel tether and jacket system (Lomir Biomedical, Malone, NY) that permitted monkeys to move freely within the home chamber. Catheter patency was periodically evaluated by intravenous ketamine (5 mg/kg) administration through one lumen of the double-lumen catheter. The catheter was considered patent if intravenous ketamine administration produced muscle tone loss within 10 s.

Monkeys were housed individually in well-ventilated, stainless-steel chambers that also served as experimental chambers. Each chamber was equipped with a custom operant panel that contained two horizontally arranged response keys, a pellet dispenser (Model ENV-203–1000; Med Associates, St Albans, VT), and two syringe pumps (Model PHM-108; Med Associates), one for each lumen of the double lumen catheter. One syringe pump (the “self-administration” pump) delivered response-contingent cocaine or heroin injections during choice sessions, and the second syringe pump (the “treatment” pump) delivered both response-contingent saline injections during saline self-administration sessions and noncontingent saline injections at a programmed rate of 0.1 mLs every 20 min. The intravenous (IV) catheter was protected by a tether and jacket system (Lomir Biomedical, Malone, NY). Catheter patency (loss of muscle tone within 10 s) was periodically evaluated by ketamine (3 mg/kg, IV) administration and after a rightward shift in the drug choice dose effect function produced by an experimental manipulation.