The sucrose preference test (SPT) is a classic behavioral test for evaluating anhedonia. Its principle is a test method designed based on the preference of rodents for sweet taste. After the animals have fasted for a period of time, they are given plain water and low-concentration sucrose water at the same time. The animals’ preference for sucrose water (sugar water preference index) is used as an indicator to determine whether the animals have anhedonia, a depressive symptom. In 1981, Katz et al. first discovered in the process of modeling depressed rats that the consumption of sucrose and saccharin water in rats after stress decreased by 50%, and further found that the tricyclic antidepressant imipramine could significantly increase the consumption of sucrose water in rats in the model group. At present, this experiment is mostly used to detect anhedonia behavior after chronic unpredictable stress.
Experimental Equipment
The SA226 sugar water preference experimental system of CYANCS uses the automatic water replenishment technology of micro-injection pump, which can accurately measure the drinking amount, eating time and drinking frequency of mice and rats. There is a position sensor in front of each water spout. Only when mice and rats enter the drinking area, the missing water is actually drunk by the mice and rats; when mice and rats are not in the drinking area, the water that evaporates naturally or drips due to vibration is automatically removed by the software.
Features
- The software supports the “one-key bottle change” function;
- Modular design of drinking water detection, convenient for position exchange;
- Use a micro-injection pump to accurately replenish water, with an accuracy of 0.01ml;
- High throughput, supporting up to 200 channels of simultaneous testing;
- Support long-term testing and water change during the test;
- Restore the cage environment to the greatest extent possible and reduce stress response;
- The software automatically filters the interference of liquid volatilization on test data;
- Drinking water events can be synchronized to third-party devices via TTL signals;
- The accuracy of drinking time is 0.01s, and the accuracy of drinking volume is 0.001ml;
- Each cage box is connected in parallel to the host, and the failure of any channel will not affect the normal test of other channels;
- Test indicators: single drinking water volume, total drinking water volume, single drinking water time, total drinking water time, drinking times, etc.
Experimental Process
- Preliminary preparation: Select adult male C57BL/6 mice (8-10 weeks old) and keep them in single cages to acclimate to the laboratory environment for 1 week. Test the conductivity of the metal mouth to ensure the sensitivity of the licking signal (false touch rate <1%); pre-experiment to verify the baseline of the number of licking water from sugar water and ordinary water bottles (the sugar water preference rate of healthy mice is >65%).
- Acclimation period: Animals need to adapt to the experimental environment and the double water bottle apparatus, usually 12-24 hours.
- Baseline test: Record the sugar preference index under normal conditions (sugar consumption/total fluid consumption × 100%).
- Intervention treatment: such as drug injection, chronic stress, etc., followed by re-measurement of the preference index.
- Final test: The experimental group received an intraperitoneal injection of fluoxetine (10 mg/kg), and the control group received an injection of normal saline; the animals were fasted for 4 hours after administration (only drinking water was provided); sugar water and ordinary water bottles were provided, and the number of water lickings was recorded continuously for 24 hours; and time-specific data were analyzed (e.g., 0-4 hours vs. 4-24 hours after administration).
Evaluation Indicators
Sugar water preference index = sucrose water consumption/(sucrose water consumption + drinking water consumption) x 100%.
Notes
(1) The sugar water preference experiment is very sensitive to environmental changes, which is a key factor affecting the success of the experiment. The test should be carried out in a separate room, keep the environment quiet, and maintain appropriate temperature and humidity during the experiment.
(2) During the baseline test phase, animals that have been trained multiple times but whose baseline is still unstable or that drink too much or too little water need to be eliminated.
Discussion and Summary
The sugar water preference experiment can evaluate whether the depression model animals have the core symptom of human depression – anhedonia, and has a high degree of credibility. The method of using the sugar water preference experiment to evaluate depressive behavior is summarized as follows:
1. Accurately obtain the amount of water you drink
The key factor is that the bottle mouth does not drip water automatically. Water only comes out when the animal licks it. Water that evaporates naturally or drips due to vibration must be deducted.
2. Experimental Mode
The sugar water preference experiment is divided into several parts: sucrose drinking water training, baseline measurement, grouping according to baseline, depression model replication and drug treatment sucrose drinking water test. This experiment is most widely used in chronic stress models. Generally, after 4 to 5 weeks of stress, the water preference index of the animal type is significantly reduced. In addition, this experiment is the most important behavioral detection method for the study of the onset rate of antidepressant drugs, so periodic detection can be performed during the drug treatment stage.
3. Judgment indicators
The sugar preference index was the main evaluation index, and the criteria for judging depressive behavior were: the sugar preference index was lower than 0.4 or significantly lower than that of the control group. The sugar preference index of rats in the blank control group was greater than 80%, and the sugar preference index of mice in the blank control group was greater than 70%.
