The aim of this procedure is to study spatial cognition in mice using variations of the water maze. Unlike other models, the water level is shallow enough to allow the mouse to paddle. Instead of swim, a mouse is placed in the center of the Mae and allowed to seek the exit.
The exits of the paddling pool are located on the sides to mimic a more natural escape response. Once the correct exit has been located, the animal is removed, and data representing spatial cognitive ability is recorded. The main advantage of the paddling pool or paddling y maze over existing techniques for testing spatial cognition, like for example, the maus water maze or the barns maze, is that it's much less stressful than the mo maze, certainly, and you don't get confounding local or factory cues as you would in the barns.Maze.
Three successive designs were made of the paddling pool mark. One is a circular pool, 85 centimeters in diameter with 12 true or force exits. Mark two is an octagonal pool, 86 centimeters in diameter with eight true or force exits set in the corners.
Lastly, mark three is a do deck agonal pool, 120 centimeters in diameter with 12 true or force exits set in the corners. Each design is built on a white base and is surrounded by transparent walls made of clear acrylic plastic. The pool is filled with 20 to 25 degrees Celsius water to reduce the swim stress sometimes found when a mouse is introduced to a deeper pool.
The water level is set at a depth of about two centimeters to encourage paddling behavior. To facilitate a more natural escape response, the animal is allowed to escape to a dry tube made of black plastic pipe set into the side of the apparatus. The false exits are occluded by a black wooden plug, whereas the true exit is open and joined to an additional pipe.
Upon entering the true exit, the mouse can be swiftly and a dramatically returned to its home cage while inside this pipe. As is true of all spatial memory tests, the mouse relies on room cues seen through the transparent walls of the apparatus. Shelves, cupboards, and black plastic shapes should be positioned on the walls to serve as distinctive visual cues.
To begin a trial, place a mouse in the center of the pool facing one of four positions on the perimeter, nine 12, or three o'clock. If the escape tube is at six o'clock, release the animal quickly when they're just above the water, instead of releasing them slowly, which may cause them to struggle and impair their initial orientation. If the mouse fails to escape by 60 seconds, manually guide them to the exit.
Using Clear Perspex paddles. Record the time to find the exit and any errors. Errors are defined as coming within a head's length from a tube or passing close by the real exit without entry.
The timer is stopped when the entire head has entered the tube. 10 trials are run for each mouse with a five minute rest between trials. Next, the paddling pool model was applied to the Y maze.
The apparatus consists of three arms made of transparent plastic each 30 by eight by 20 centimeters. This is mounted on a white base and filled with shallow water.Again. There is only one true exit with the other two arms terminating in false exits.
To start a trial in the paddling y maze place a mouse at the end of one of the closed arms facing away from the center. If the mouse fails to exit by 60 seconds, manually guide them to the exit. Using Clear Perspex paddles take measures of the total time to exit and the number of errors the paddling y maze can be used without water.
To test for spatial novelty memory, begin by placing a thin layer of wood chip bedding on the floor of the Y maze. To enrich the olfactory environment, allow one or two non-experimental mice to explore the maze for a few minutes before the experiment starts. Then remove olfactory cues by mixing up the sawdust.
This helps ensure that the next mouse will have to rely on spatial cues. Insert a transparent guillotine door to cover the exit hole at the end of the exit arm and an opaque guillotine door to seal the arm off from the other two. During the first phase of the test, place the mouse in the start arm and allow it to explore freely.
Record the number of entries and times spent in each charm. After the mouse is explored for five minutes, remove the animal and raise the opaque door to allow free access to all three arms. Reintroduce the mouse to the start arm and observe it for two minutes.
Note the number of entries and the time spent in each arm.Control. Mice should remember the first two arms and spend more time. In the previously inaccessible novel arm, hippocampal lesions greatly impair learning in the paddling pool.
In this example, performance in the dry y maze revealed impairments in spatial novelty memory in mice with a knockout of the glutamate receptor. A AMPA receptor subunits. Unlike the path length and escape time measures in the Morris water maze, the error rate in the paddling pool for hippocampal lesioned mice remained constant throughout the training period.
So this represents a pure measure of spatial memory as opposed to escape time or path length, which both decreases the mice become acquainted with the nons spatial elements of the task. The errors measure also provides a greater magnitude of difference between impaired mice and controls. While attempting the paddling pool or Y MAs tests, it's important to remember always to sit in the same position because the experiments of themselves act as a spatial cue.
We once had visitors from EMBO, European Molecular Biology Organization, including two noble laureates, and the presence of them there disrupted the performance of the mice. So before you start the paddling pool, please clear away all the Nobel Laureates from the immediate vicinity.
