Syringe pump

Operant oral self-administration training and testing was performed in clear polycarbonate/aluminum modular operant test chambers en-cased in individual sound-attenuating and ventilated environmental cubicles (66 × 56 × 36 cm) (Med Associates, Inc., St. Albans, VT). Each chamber had grid floor and two retractable levers on the same side wall. Two syringe pumps (Med Associates, St. Albans, VT) located outside the chambers dispensed either ethanol or water through two different polyethylene tubing into two stainless steel drinking cups mounted 2 cm above the grid floor in the middle of one wall. The two retractable levers were located 3.2 cm to either side of the drinking cups. Fluid delivery and recording of operant responses were controlled by microcomputers.

The self-administration boxes consisted of operant conditioning chambers (Med Associates, Inc., St. Albans, VT) enclosed in lit, sound attenuating, ventilated environmental cubicles. Each chamber was equipped with two retractable levers located in the front panel, laterally to a food pellet magazine. A pellet dispenser was positioned behind the front panel of the boxes. Chambers were also equipped with auditory stimuli presented via a speaker and visual stimuli located above the levers (cue light). Infusions occurred by means of syringe pumps (Med Associates, Inc., St. Albans, VT) and liquid swivels (Instech Solomon, Plymouth Meeting, PA) connected to plastic tubing protected by a flexible metal sheath for attachment to the external catheter terminus. To allow delivery of nicotine, an infusion pump was activated by responses on the right (active) lever, while responses on the left (inactive) lever were recorded but did not result in any programmed consequences. Activation of the pump resulted in a delivery of 0.1 mL of the reinforcer. A microcomputer controlled the delivery of nicotine, presentation of auditory and visual stimuli, and recording of the behavioral data.

Training took place in 20 Med Associates (St. Albans, VT) operant test
chambers. Each chamber measured 30.5 × 24 × 29 cm and had aluminum
front and rear walls with clear polycarbonate side walls. Three Med-Associates
retractable levers were located on the front wall of the chamber. Saccharin
reinforcers were provided by operation of a Med-Associates retractable sipper
tube and bottle containing a 0.2% saccharin solution. The aperture through which
the sipper tube inserted was located above the middle lever. A 100-mA cuelight
was located above the left and right levers. A speaker was located in the center
of the front wall near the ceiling. A 100-mA houselight was located at the rear
of the chamber near the ceiling. Heroin (provided by the Drug Supply Program,
National Institute on Drug Abuse, Bethesda, MD) in a saline solution at a
concentration of 0.1 mg/ml was infused at a rate of 6.5 ml/min by 20-ml syringes
driven by Med-Associates (St. Albans, VT) syringe pumps. Tygon tubing extended
from the 20-ml syringes to a 22-gauge rodent single-channel fluid swivel
(Instech Laboratories, Plymouth Meeting, PA) and tether apparatus (Plastics One,
Roanoke, VA) that descended through the ceiling of the chamber. Heroin was
delivered to the subject through tubing that passed through the metal spring of
the tether apparatus.