Induction and Evaluation of Depression in Mice Through Chronic Stress Exposure

Induce depression in a test mouse through exposure to chronic stress and compare it to a control mouse.

Apply daily stressors to the test mouse, including food and water deprivation, confinement in a restrainer, isolation in a cage without bedding, placement in a wet or crowded cage, and forced swimming in ice-cold water.

These stressors trigger the release of corticosterone, a stress hormone.

Corticosterone binds to its receptors on neurons, causing an excessive release of glutamate, an excitatory neurotransmitter.

Excessive glutamate over-activates calcium-permeable ionotropic receptors, inducing continuous calcium influx, which results in neuronal death, a process called excitotoxicity. 

The loss of neurons in the hippocampus and prefrontal cortex, regions essential for mood regulation, disrupts signal transmission and triggers symptoms of depression.

Compared to the control mouse, observe changes in coat condition due to stress-induced reductions in grooming behavior and weight loss due to reduced appetite in the test mouse, indicating depression.

To induce depression, expose mice daily to any two of the following seven stressors for 21 consecutive days. Expose mice to food deprivation by emptying the feed of each cage, or water deprivation by removing the water bottle for 24 hours. Expose mice to restrained stress, where the mouse is restrained in a small plastic tub for three hours, or an empty cage with the padding removed. As another option, expose mice to wet and soiled cages by pouring water into each cage and keeping wet for 24 hours.

Expose mice to crowded cages, in which five mice are placed in one cage for 25 hours. For the last option, expose mice to ice cold swimming by forcing each mouse to swim in a clear glass aquarium with ice water for five minutes. Finally, record the coat state and body weight weekly until the end of modeling at day 21, and calculate the total score of the coat's state.