Details of the rMOG
Opertech Bio follows the highest standards of husbandry and veterinary care for the welfare of our animal taste testers. All of our protocols are subjected to rigorous evaluation and approval by the Institutional Animal Care and Use Committee (IACUC) of the Albert Einstein Healthcare Network. Our expert taste testers enjoy their taste testing sessions and view them as a recreational activity. They are well fed, live a full life cycle, and are never subject to any invasive procedures.
Taste quality measurement is achieved through the experimental paradigm of operant taste discrimination. Rats are trained to press two levers for a food pellet reward after they have tasted sample solutions presented to them in a 96-well plate. To receive the reward, the rats must press the right lever if the solution is a standard (for example, a sweet sugar solution) and the left lever if the solution presented has any other taste. By comparing the percentage of the presses on the right (standard) lever, the degree of similarity between a novel taste stimulus and the taste standard can be quantified.
Palatability of the sample solutions in the 96-well plate is determined by a laser beam counting the number of times a rat licks the sample. The more licks the more palatable.
Schematic diagram depiction of the central components of the Microtiter Operant Gustometer (MOG), the first high throughput chemosensory system for in vivo testing.
Opertech owns 8 Microtiter Operant Gustometers. The MOG technology is protected by U.S. and foreign patents and patent applications.
Because of its ability to measure both taste quality and palatability in a high throughput capacity, the rMOG has proven particularly useful in the discovery of new flavor ingredients. MOG-trained rats are exceptionally efficient at screening large collections of natural products or other compounds for desirable taste properties. They also provide the ability to evaluate compounds not yet approved for use by humans. On behalf of our clients we have used our rMOG to discover novel all natural sweeteners and sweetness enhancers that have been subsequently validated with human taste panels and are currently under consideration for development.
The video shows an experienced rat performing taste evaluations of two consecutive trials. The rat has been trained to press the right lever when it tastes something sweet and the left lever when it tastes anything that is not sweet.
Before the start of each trial, the levers are withdrawn behind the front panel. The slots through which the levers extend are visible to either side of a rectangular receptacle for food pellets, and stimulus lights that illuminate at the beginning of a trial can be seen above each of the slots.
Immediately below the food pellet receptacle on the front-most edge of the floor is a trap-door covering a 5 mm diameter aperture. The X-Y motion table, appearing in the lower right corner of the video, moves the plate into position just prior to the beginning of the trial.
The start of a trial is signaled to the rat by the sounding of a tone. When the rat hears the tone it knows that the trap door over the aperture has opened, giving access to a taste sample. The sample is available through the aperture in a single well from the 96-well plate located just beneath the floor of the chamber.
As soon as the rat inserts its tongue into the well, a laser beam projected across the top of the well is disrupted, triggering a switch that turns on the stimulus lights and releases the levers.
The first trial is of 300 mM sucrose (about a 10% solution). The rat licks over 30 times, each lick being recorded by the computer. This many licks indicates a highly palatable sample. When the rat finishes licking, it makes its choice based on the taste of the solution. In this case, the correct choice is the right lever which it depresses 10 times—this rat accomplishes the lever presses with its mouth! The lever pressing operated a food pellet dispenser and the rat quickly retrieves its reward from the receptacle.
The next, randomly designated well is then aligned with the aperture and the next trial begins after a 30-second inter-trial interval. This time the solution presented in the well is 1 mM quinine, which is noticeably bitter. Since quinine is unpalatable the rat licks only a few times from the well before making the correct choice of the left lever for a food reward.