Env 001

Training and testing procedures were conducted in seven standard operant conditioning chambers equipped with three retractable levers, a food pellet dispenser and fan on the front panel, a 28-V house light on the back panel, and housed within sound-attenuating shells (ENV-001; Med Associates Inc. St. Albans, Vermont, USA). Experimental events were controlled using Med-PC IV software (version IV; Med Associates Inc.). Dustless Precision Pellets (45 mg; Product# F0021; BioServ, Flemington, NJ) were used as reinforcements for lever pressing.

All training and testing sessions were conducted in standard two-lever operant conditioning chambers (ENV-001; MED Associates, St. Albans VT). Two response levers were located on either side of a recessed food tray. Located above each lever was a white cue light. Nicotine infusions were delivered by a syringe pump, and food pellets were delivered by a pellet dispenser. A computer, linked to a MED Associates interface, recorded responses and controlled infusions during sessions. Each chamber was modified to allow access to two 100 mL Richter feeding tube glass bottles (Model 900010; Dyets, Inc., Bethlehem PA) on the wall of the chamber opposite the levers. The design of the bottles allowed them to be fixed to the chambers with lipped feeding tube holders (Model 901100; Dyets, Inc., Bethlehem, PA) such that only the drinking spout could be accessed by rats while inside the chambers.

Lever press training, AMP self-administration and AMP-seeking tests were conducted in standard operant conditioning chambers (ENV-001, Med Associates, St. Albans, VT, USA) enclosed in a sound-attenuating and ventilated cubicle. AMP or SAL infusions were administered via a syringe pump (PHM-100, Med Associates) connected to a 10-ml syringe (Arndt, Garcia, et al., 2015 ;Arndt, Johns, et al., 2015 (link); Garcia et al., 2019 (link); Garcia & Cain, 2020 (link)).

Lever press training and AMP SA were conducted in standard operant conditioning chambers (ENV-001, Med Associates, St. Albans, VT). Each chamber was enclosed in a sound-attenuating compartment and operated by a computer interface using MedPC software. During lever press training, sucrose was delivered with a liquid dispenser in a recessed food receptacle. Stainless steel operant response levers were located on each side of the food receptacle 7.3 cm above the metal grid floor. A 28-V, 3-cm diameter white cue light was centered above each response lever. AMP was infused with a mechanical syringe pump (PHM-100, Med Associates) (Arndt, Johns et al. 2015 (link), Arndt, Wukitsch et al. 2019 (link), Garcia, Arndt et al. 2019 (link)).

Standard operant conditioning chambers (28 × 21 × 21 cm; ENV-001; MED Associates, St. Albans, VT) with alternating aluminum and Plexiglas walls including a metal rod floor were located inside sound-attenuating chambers (ENV-018M; MED Associates, St. Albans, VT). A recessed food tray (5 × 4.2 cm) was located 2 cm above the floor in the center of one of the aluminum walls, and a response lever was located 6 cm above the floor on each side of the food tray. A white stimulus light (28 v, 3 cm diameter) was located 6 cm above each lever. The standard operant chambers were retrofitted with a counterbalance arm, swivel, and leash (PHM-110, PHM-115I and PHM-120A, respectively; MED Associates, St. Albans, VT). Drug infusions were delivered via a MED Associates infusion pump located outside of the sound-attenuating chamber (PHM-100; MED Associates, St Albans, VT). Responses were recorded and programmed consequences were controlled by a computer in an adjacent room equipped with Med-PC software (Med Associates, St. Albans, VT).

Sessions took place in eight stainless-steel operant chambers (Med-Associates, Georgia VT, model ENV-001) with a gridded floor measuring L 28 x W 21 x H 21cm. The chambers were placed two to three feet apart and located around the perimeter of the sound and light attenuated experimental room that is designed for undergraduate courses in Learning & Conditioning, and Behavioral Pharmacology. The room measured L 16.5 × 9 ft. An antenna-less/cable-less television set delivered a white noise source that was initiated at the start of each session and terminated at the end of the session manually. Overhead recessed incandescent track lights controlled by a dimmer switch produced approximately 15 watt lighting during session time and was terminated at the end of each session by manually turning on the bright overhead fluorescent lighting. Each operant chamber was equipped with one lever located 2 cm to the left of the centrally-located food magazine (which delivered standard 45 mg food pellets, BioServe, Frenchtown, NJ) and 7 cm above the grid floor. stimulus light, which functioned as the CS target, was located directly above the lever. On Pavlovian test sessions an infrared video camera (Sony, Digital Handycam, cassette recorder - 120X) was placed on a tripod approximately 2 feet from the side door but focused on the food magazine and lever.

Conditioning was performed in an operant chamber (Med Associates, ENV-001, St. Albans, VT). The chamber was enclosed within a sound-attenuating cabinet (Med Associates). Each cabinet was affixed with an IR-sensitive digital camera (Fire-i, Unibrain, San Ramon, CA), infrared lighting, and dim white house lighting (20 lux). There was a fan in each cabinet that provided airflow and ~60 dB of ambient noise. The chamber was also fitted with 2 levers, one designated as the active lever and the other designated as the inactive lever, a cue light placed proximal to the levers, and a food receptacle where sucrose pellets were delivered.