Sound attenuating chamber

Rats were trained in Med Associates operant boxes housed in individual sound-attenuating chambers (Med Associates, St Albans, VT, USA). operant boxes were fitted with 2 levers (active and inactive), a stimulus light located directly above the active lever, speaker, and house light. All boxes were controlled by Med-PC IV software (Med Associates, St Albans, VT, USA). Rats were first trained in 2 hr sessions on a fixed-ratio 1 (FR-1) schedule. Active lever presses resulted in a 0.5μg infusion of fentanyl delivered in 50μl of sterile saline over 3.6s. Each infusion was paired with stimulus light (white light) and tone (78 dB, 2900 Hz) and was followed by a 20-sec time out signaled by termination of the house light. Rats were trained for a minimum of 6 sessions and to a criterion of > 25 infusion for 3 consecutive sessions.

Experimental sessions were conducted in operant conditioning chambers for rats (MED Associates, St. Albans, VT, USA) housed inside sound-attenuating chambers (MED Associates). Each operant conditioning chamber contained two retractable levers, with a stimulus light above each lever, and a house light. One lever was designated as the active lever and the other lever was designated as inactive. The side of the operant conditioning chamber associated with the active lever was counterbalanced across subjects. Fans provided ventilation for each chamber and speakers provided white noise. Infusion pumps (Med Associates) were located outside the chamber. Experimental events were arranged and recorded by MED-PC software (Med-Associates).
A Thermo Scientific CoulArray Multi-Channel ECD Array system (model 5600A; Thermo Scientific, Waltham, MA, USA) was used to analyze neurotransmitter concentrations. The array detector contained 16 coulometric electrochemical cells that provided quantitation of multiple neurotransmitters and metabolites simultaneously. An Agilent 1100 HPLC System (Santa Clara, CA, USA) and an Applied Biosystems API 4000 Triple Quadrupole liquid chromatography mass spectrometer (LC-MS) with Turbo Ion Spray source (Foster City, CA, USA) were used for quantitation of GLU.

On the testing day, 8 week old mice were transported to the testing room between the hours of 0900 and 1100 and were habituated for two hours. Locomotor activity was assayed using infrared activity monitors (Accuscan, Columbus, OH) surrounding an open field of 8×8×11 inches. Distance traveled was monitored for a period of two hours. Two acrylic boxes fit inside a single Accuscan monitor, enabling us to test two animals simultaneously. Whether another animal is present in the second box affects locomotor behavior in this assay (D.J.S and A.S.P., personal observations). We found that testing two animals from different home cages in a single Accuscan monitor both reduced variability and allowed high-throughput rates. Activity monitors were themselves housed inside sound-attenuating chambers (Med-Associates) equipped with lights and fans, both of which were turned on during the testing session. Acrylic boxes were rinsed with hot water and dried and then wiped down with a solution of 2.5% glacial acetic acid between testing sessions (Speca et al. 2006 (link)).