Pellet dispenser

Manufactured by Med Associates

Sourced in Sao Tome and Principe

The Pellet Dispenser is a laboratory equipment designed to accurately and consistently dispense small quantities of pelletized materials. It features a motorized feed mechanism that allows for precise control over the amount and rate of pellet delivery. The device is intended for use in various scientific and research applications that require the controlled distribution of pelletized substances.

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Lab products found in correlation

14 protocols using pellet dispenser

Operant Conditioning Chambers for Animal Behavior

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Two experimental chambers (Med Associates, Inc.), each measuring 29 cm long by 25 cm wide by 28.5 cm high, were located within sound- and light-attenuating enclosures each equipped with a ventilation fan. Two response keys, spaced 16 cm apart center to center, were mounted on the front panel of the chamber, 23.5 cm above the grid floor and 3.5 cm from the side walls of the chamber, and could be transilluminated with white, red, and green light. A clicker was used to provide auditory feedback for all key pecks during a trial. A triple-cue light, centered on the panel and equipped with a green, yellow, and red bulb, was located 26.5 cm above the grid floor. A food magazine was mounted on the center of the panel, 4 cm above the grid floor, and equipped with a 7-W white light that was illuminated during reinforcement. A pellet dispenser (Med Associates, Inc.), situated behind the front panel, delivered 20-mg precision food pellets (TestDiet®) at the rate of one pellet every 0.3 s. pellet dispensers were tested daily and on those rare occasions when a pellet dispenser became jammed during a session, the respective data were not used. A 7-W houselight was mounted centrally on the ceiling of the chamber. Med-PC™ software (Med-Associates, Inc.) was used to control experimental events and record responses.

Oliveira L., Green L, & Myerson J. (2014). PIGEONS' DELAY DISCOUNTING FUNCTIONS ESTABLISHED USING A CONCURRENT-CHAINS PROCEDURE. Journal of the experimental analysis of behavior, 102(2), 151-161.

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Operant Conditioning Chambers for Self-Administration

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The operant conditioning chambers (Med Associates, VT, USA) contained an active and inactive lever, a cue light, and a tone generator as previously described in Pentkowski et al.¹⁶. The chambers contained either an infusion pump (Med Associates) connected to a liquid swivel (Instech, PA, USA) and attached to a polyethylene tubing sheltered within a metal leash (PlasticsOne, VA, USA) or contained pellet dispensers (Med Associates). All operant conditioning chambers were housed within sound attenuating boxes that contained a ventilation fan. Male and female rats underwent self-administration in different rooms to avoid potential confounding influences of sex on behavior.

Garcia R., Le T., Scott S.N., Charmchi D., Sprout J.M., Pentkowski N.S, & Neisewander J.L. (2020). Preclinical support for the therapeutic potential of zolmitriptan as a treatment for cocaine use disorders. Translational Psychiatry, 10, 266.

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Operant Conditioning in Primate Neuroscience

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During sessions, monkeys were seated in chairs (Primate Products, Miami, FL) located in ventilated, sound attenuating chambers, which were equipped with response panels containing stimulus lights, two response levers, and pellet troughs. Food pellets (5TUT, Test Diet, Richmond, IN) were delivered to the troughs by pellet dispensers (Med Associates, Inc., St. Albans, VT) located outside of chambers. Self-administered drug was delivered to catheters from syringes placed in syringe drivers (model PHM-100; Med Associates, Inc., St. Albans, VT) outside of chambers. Syringes were connected to ports by 183-cm catheter extension sets (Baxter Healthcare, Deerfield, IL) and 20-g Huber-point needles (Access Technologies, Skokie, IL). The infusion rate was 2.3 ml/min (monkeys JA and KI) or 3.4 ml/min (monkeys HU and MU). A computer used MedPC IV software (Med Associates, Inc., St. Albans, VT) to control experimental events and collect data. White noise was provided in each chamber.

Gerak L.R, & France C.P. (2021). Effects of buprenorphine/lorcaserin mixtures on preference for heroin, cocaine, or saline over food using a concurrent choice procedure in rhesus monkeys. Drug and alcohol dependence, 227, 108991.

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Behavioral Testing of Monkeys in Primate Chairs

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During behavioral testing, monkeys sat in a primate chair inside a ventilated 3 ft × 2 ft × 4 ft test cubicle. The chair was held in place by clamps. A 15” touch-screen color monitor was affixed to the far wall of the box, 22 cm in front of the monkeys' eyes. Pellet dispensers (Med Associates) delivered rewards through a tube connected to a cup located centrally under the monitor, within the monkeys' reach. Touch-screen monitors and reward dispensers were under computer control. Rewards consisted of 190-mg banana-flavored pellets (TestDiet). White noise was played during testing to prevent distractions from extraneous sounds.
Stimuli used for shaping and instruction stimuli (IS) for the main task were chosen from a large collection of images of people, objects, and landscapes downloaded from the internet in the public domain and edited to 400 × 400 pixels. Images were stored as .bmp files and, when presented on the monitor, subtended around 40 degrees of visual angle. Target stimuli (TS) consisted of three identical, solid, white squares of dimensions 3 cm × 3 cm, which appeared in fixed locations on the monitor: 8 cm above, to the left, and to the right of the screen's midpoint.

Yang T., Bavley R.L., Fomalont K., Blomstrom K.J., Mitz A.R., Turchi J., Rudebeck P.H, & Murray E.A. (2014). Contributions of the hippocampus and entorhinal cortex to rapid visuomotor learning in rhesus monkeys. Hippocampus, 24(9), 1102-1111.

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Operant Conditioning Paradigm in Monkeys

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Monkeys’ home chambers also served as the experimental chambers, and were equipped with an operant response panel, which had 2 response levers and 3 stimulus lights above each lever. The lights over the left and right levers were white and red, respectively. Chambers were also equipped with a pellet dispenser (Med Associates, St. Albans, VT) that delivered food pellets to a receptacle within the chamber. The external section of the intravenous (IV) catheter was routed through a jacket and tether system (Lomir Biomedical, Quebec, Canada) to the rear of the chamber and connected to a peristaltic fluid pump (Cole-Parmer, Chicago, IL). Catheter patency was periodically evaluated with IV ketamine (4 mg/kg) administration, and the catheter was considered patent if IV ketamine administration produced overt loss of muscle tone within 20 s.

Lile J.A., Johnson A.R., Banks M.L., Hatton K.W., Hays L.R., Nicholson K.L., Poklis J.L., Rayapati A.O., Rush C.R., Stoops W.W, & Negus S.S. (2019). Pharmacological validation of a translational model of cocaine use disorder: Effects of d-amphetamine maintenance on choice between intravenous cocaine and a non-drug alternative in humans and rhesus monkeys. Experimental and clinical psychopharmacology, 28(2), 169-180.

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Operant Conditioning in Singly-Housed Mice

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Mice were singly housed during the course of the experiments. Operant chambers were made from black, opaque plastic boxes (22 cm x 35 cm x 23 cm). Chambers included an active and inactive lever and a pellet dispenser (Med-Associates, St. Albans). Above each chamber was a PlexBright Compact LED module attached to a PlexBright LED Commutator which allowed the fiber optic cable to spin freely as the animals moved in the chambers (Plexon, Dallas). Mice were weighed daily immediately prior to testing. 60-minute sessions began after the fiber optic was attached and the animal placed in the chambers. Mice were allowed to press both the active and inactive lever at will during the session.

Gnazzo F.G., Mourra D., Guevara C, & Beeler J.A. (2021). Chronic food restriction enhances dopamine mediated intracranial self-stimulation. Neuroreport, 32(13), 1128-1133.

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Progressive Ratio Operant Conditioning in Mice

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mice were singly housed in standard mouse polycarbonate mouse cages equipped with two levers, pellet dispenser and food hopper (Med-Associates, Fairfax, VT). No food restriction was employed and the only source of food was through lever pressing (closed economy) except in the concurrent choice test. 20 mg grain pellets (Bio-Serv, Flemington, NJ) were dispensed on a progressive ratio schedule with an increment of two such that the first pellet cost 2 lever presses, the next 4, the next 6 and so on (PR2). After 30 minutes of inactivity (no lever press on active or inactive lever), the ratio reset to 2 to start the sequence again. This allows the mice to titrate their average cost per pellet by balancing the size of meals (with larger meals proportionally more expensive) against the number and frequency of meals (Fig 1A). In the homecage concurrent choice, mice were provided free chow in their cage and could earn sucrose pellets (Bio-Serv, Flemington, NJ) through lever pressing on a PR2 schedule. In experiments with running wheels, radio-telemetry running wheels (Med-Associates, Fairfax, VT) were fit in the operant-equipped cages and running was monitoring 24/7 in 1 min bins.

Mourra D., Gnazzo F., Cobos S, & Beeler J.A. (2019). STRIATAL DOPAMINE D2 RECEPTORS REGULATE COST SENSITIVITY AND BEHAVIORAL THRIFT. Neuroscience, 425, 134-145.

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Rat Lever Press Conditioning Paradigm

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Prior to the onset of PCA testing, rats were handled daily for 3 days and given ~7 banana-flavored sucrose pellets (45 mg; BioServ). Rats were tested in conditioning chambers (20.5 x 24.1 cm floor area, 20.2 cm high; MED Associates Inc.). Each chamber contained a food magazine port located 2.5 cm above the floor in the center of the intelligence panel, a red house light located on the wall opposite the food magazine port (on throughout training sessions), and a retractable lever (Med Associates) located 2.5 cm to the left or right of the food receptacle and 6 cm above the floor. This retractable lever was illuminated when extended with a white LED light placed inside the lever house. For a lever press to be recorded, a force of ∼15 g was needed. The pellet dispenser (Med Associates) delivered one 45 mg banana-flavored sucrose pellet (Bio-Serv) into the food magazine port at a time. A head entry was recorded each time a rat broke the infrared photobeam located inside the food magazine port. Each conditioning chamber was placed in a sound-reducing enclosure and a ventilating fan generated background noise. Data collection was controlled by Med-PC IV Behavioral Control Software Suite.

Avila C, & Sarter M. (2024). Cortico-striatal action control inherent of opponent cognitive-motivational styles. bioRxiv.

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Primate Cocaine Self-Administration Assay

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Behavioral sessions were carried out in ventilated, sound-attenuating chambers (1.5 x 0.74 x 0.76 m; Med Associates, East Fairfield, VT) designed to accommodate a primate chair. An intelligence panel (48 x 69 cm) was located on the right side of the chamber that contained two photo-optic finger-poke apertures (Model 117–1007; Stewart Ergonomics, Inc., Furlong, PA) on each side with a horizontal row of three stimulus lights positioned 14 cm above each finger poke. For these studies, cocaine was available by responding on one of the two finger-pokes (switches) and the active switch was counterbalanced between monkeys. A food receptacle was located between the switches and connected with a Tygon tube to a pellet dispenser (Med Associates) located on the top of the chamber (food-reinforced responding was not examined in these monkeys). A peristaltic infusion pump (7531–10, Cole-Parmer Co., Chicago, IL) for delivering drug injections at a rate of approximately 1.5 ml/10 sec was also located on the top of the chamber. White noise was continuously present in the room to mask extraneous noise.

John W.S, & Nader M.A. (2016). EFFECTS OF ETHANOL ON COCAINE SELF-ADMINISTRATION IN MONKEYS RESPONDING UNDER A SECOND-ORDER SCHEDULE OF REINFORCEMENT. Drug and alcohol dependence, 170, 112-119.

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Gerbil Auditory Behavior Testing Setup

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The behavioral setup was similar to Paraouty et al.^{46 (link)}. Gerbils were placed in a plastic test cage (dimensions: 0.4 × 0.4 × 0.4 m) that was housed in a sound attenuation booth (Industrial Acoustics; internal dimensions: 2.2 × 2 × 2 m), and observed via a closed-circuit monitor. Auditory stimuli were delivered from a calibrated free-field tweeter (DX25TG0504; Vifa) positioned 1 m above the test cage. Sound calibration measurements were made with a ¼ inch free-field condenser recording microphone (Bruel & Kjaer). A pellet dispenser (Med Associates Inc, 20 mg) was connected to a food tray placed within the test cage, and a nose port was placed on the opposite side. The nose port and food tray were equipped with IR emitters and sensors (Digi-Key Electronics; Emitter: 940 nm, 1.2 V, 50 mA; Sensor: Photodiode 935 nm 5 nS). Stimuli, food reward delivery, and behavioral data acquisition were controlled by a personal computer through custom MATLAB scripts and an RZ6 multifunction processor (Tucker-Davis Technologies).

Paraouty N., Rizzuto C.R, & Sanes D.H. (2021). Dopaminergic signaling supports auditory social learning. Scientific Reports, 11, 13117.

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