Medstate notation

Each rat was trained in one of 12 identical operant chambers (Med Associates, St. Albans, VT) measuring 30.5×24.0×29.0 cm and housed in light and sound attenuating cubicles. All chambers have clear Plexiglas tops, fronts, and backs. Sidewalls are aluminum. The floors consist of 19 stainless steel rods (4.8 mm) spaced 1.6 cm apart center to center. Each chamber is equipped with three retractable operant sipper tubes (spouts) that enter the left side of the chamber through 1.3 cm diameter holes spaced at 8.0 cm center to center. A stimulus light is located 6 cm above each spout. A lickometer circuit is used to record spout licks (and contacts such as nose pokes). Each chamber is equipped with a house light (25 W), a tone generator (Sonalert Time Generator, 2900 Hz), and a white noise speaker (75 dB). Self-administration is controlled by an electronic circuit operating a syringe pump (Med Associates). Collection of the data and control of chamber events were performed using a Windows-based computer. Programs were written in Medstate notation language (Med Associates).

Testing was conducted in 12 self-administration chambers as previously described [32 (link)]. Each operant chamber was equipped with three retractable sipper tubes that entered the chamber through three holes. A stimulus light was located above each tube. A lickometer circuit was used to monitor licking on the leftmost saccharin spout, the middle inactive spout (the spout upon which responding elicited no consequence), and the rightmost active spout (the spout upon which a set of fixed ratio (FR) responses led to an i.v. infusion of drug). Each chamber also was equipped with a house light (25 W), a tone generator, and a speaker for white noise. Events in the chamber and collection of the data were computer controlled on-line using programs written in the Medstate notation language (MED Associates, Inc., St. Albans, VT).

Studies were conducted in sound-attenuating boxes containing modular acrylic and metal test chambers (29.2 × 30.5 × 24.1 cm; Med Associates, St. Albans, VT). Each chamber contained two retractable response levers (4.5 cm wide, 2.0 cm deep, 3.0 cm above the floor), three stimulus lights (red, yellow, and green) centered 7.6 cm above the lever, and a liquid dipper along one of the chamber walls. In addition, sonalert modules (2900 and 4500 Hz) were placed in the upper left and right corners of the chambers, respectively. Custom programs written in Med-State notation (Med Associates) controlled experimental parameters and data collection.