Barnes Labyrinth--The Behavioral Research Method of Learning Memory (4)

The Barnes maze is a model invented in 1979 by American scholar Carol A Barnes to detect spatial memory in animals. Similar to the water maze and the radial arm maze, the Barnes labyrinth is built using the characteristics of rodents in the dark and loved to explore. The enhancements obtained by the animals escaped from a bright, open platform into a dark, narrow box under the platform. This box is called the target box. After training, the animal learns and remembers the location of the target box. The model is less irritating to animals and does not require fasting like the radial arm maze, nor is it as stressful as a water maze. Therefore, it is more commonly used in memory research. It is especially useful for stress-related memory studies and behavioral phenotypic studies in knockout mice.

(I) Experimental equipment The Barnes maze produced by different manufacturers is roughly the same. Here is the Barnes Labyrinth developed by Shanghai Xinsoft Information Technology Co., Ltd. It is a circular platform made of reinforced medical organic plates that can be rotated and has a diameter of 122cm. There are 18 or 40 equidistant round holes around the platform for rats and mice; the diameters of the holes are 10cm and 5cm respectively. One of the holes (called the target hole) is connected to a black box (ie, the target box). Other round holes are hollow and are not associated with any objects. The black box is arranged in a drawer for easy removal of the animal. The target box is not visible from the surface of the platform. The labyrinth is raised 140cm. Animals can escape to the target box through the target hole. There are also different considerations for the setting of the mouse Barnes Maze. For example, some shorten the diameter of the labyrinth (such as 88cm), and the number of holes is also reduced (for example, 12), and the diameter of the hole is equivalent to the above. It is believed that such an arrangement is advantageous for increasing the rate of mouse acquisition. But regardless of which setting is used, the experimental operation is similar. Through training, the animal gains spatial positioning of the target hole.

(2) Experimental methods

1. One day before the start of the experiment, the animals were individually placed in the target box for 4 min from the target hole.

2. The animals were placed in a plastic drum (20 cm in diameter and 27 cm in height) in the center of the maze to limit activity for 5 s.

3. Remove the drum and start the timer. The experimenter observes after the curtain. When the animal's limbs enter the target box, it is counted as an escape and the animal stays in the box for 30s. Each animal was observed for up to 4 minutes at a time. During this time if the animal still can't find the target box, remove the animal from the labyrinth, place it in the target box and stay for 30s. Use this gap to clean the maze. Animals were trained twice a day for 5 to 6 days.

4. Starting from the second training, the maze is randomly rotated one to several holes before each training, but the target box is always fixed in the same orientation. The purpose of this is to prevent the animal from relying on the smell, rather than relying on memory to determine the location of the target hole.

The experiment records the following parameters: the latency of any hole, the latency to reach the target box, and the number of errors per animal (one error is defined as the animal's head to or explore any non-target hole, including focusing on the same non-target hole ).

(3) Precautions

1. The memory of the animal is weakened, mainly because the number of errors before the animal successfully obtains an escape is higher than that of the control group, and the latency of reaching the target box is extended. The incubation period of exploring any hole can be extended or not significantly changed. The memory enhancement is reversed, that is, the number of errors is reduced, and the latency to reach the target box is shortened.

2. The smell left by the animal in the maze has a great influence on the maze operation of the next animal. Therefore, in addition to rotating the maze between trainings, the labyrinth is cleaned with 70% alcohol to eliminate the guiding effect of residual odor on the next animal.

3. The Barnes labyrinth platform resembles a large open field, and any factors that affect open-box behavior (spontaneous activity), such as drug treatment or genetic modification, can affect the results of the experiment.

4. Differences in strains The love-searching properties of mice make them ideal animals for Barnes labyrinth studies, but the behavior of mice of different strains varies widely in this experiment. For example, 129S6 mice have little inquiry behavior in the Barnesian maze, making it difficult to find the target hole. The C57BL/6J mice have considerable inquiry behavior and are suitable for the Barnes labyrinth experiment. This is especially important in the study of memory in genetically altered mice.