Place the rodent in animal cages, 1% to 2% sucrose water and regular drinking water were provided simultaneously to the animals. If the animals’ preference for the sugar water decreased, it indirectly indicated that the animals might have an anhedonia, which can be used as an important criterion for evaluating the effectiveness of the depression model. Antidepressant drugs can restore the animals’ preference for sugar water.
Therefore, in various studies, it shows Sucrose Preference Test is widely in used in assessing motivation, depression (and anhedonia) and related emotional states etc.
However, during the traditional Sucrose Preference Test, researchers often encounter the following series of problems:
• In traditional experiments, researchers need to frequently change the sucrose water bottles and clear water bottles. For instance, during experiments lasting for several days, researchers have to manually record the animals’ drinking behavior every day, including the consumption of sucrose water and pure water. This process is not only time-consuming and labor-intensive but also prone to human errors in recording, such as inaccurate recording times or reading the scale with deviations.
• After each bottle change, thorough cleaning and disinfection are also required to prevent cross-contamination. If the operation is not standardized, it may lead to the animals ingesting contaminated liquids, which can affect the experimental results.
2. Lack of real-time monitoring
• Traditional methods cannot provide real-time information on the animals’ drinking behavior. Researchers can only check the scale changes of the bottles at certain intervals (such as every few hours or daily) to estimate the animals’ water intake. This makes it impossible to accurately grasp the dynamic information such as the animals’ drinking preferences and frequencies at different time periods (such as day and night).
3. Difficult to operate multiple channels simultaneously
• When conducting sucrose water preference experiments on multiple groups of animals simultaneously, traditional techniques find it hard to achieve synchronized operation. For example, in the Sucrose Preference experiment with dozens of animals, it is almost impossible to precisely synchronize the recording of each animal’s sucrose water and clear water consumption through manual operation. This significantly reduces the repeatability of the experiment and the comparability of the data.
In terms of Data accuracy:
1. Large data deviations and errors.
Manual reading of the scale to measure the consumption of liquid is prone to errors. For instance, unclear scale lines or bottle tilting can lead to inaccurate readings. Moreover, during the recording process, memory bias may occur, and researchers might unconsciously make subjective judgments on certain data, thereby affecting the authenticity and objectivity of the data.
In traditional sucrose preference test, the evaporation of liquids is also a problem that cannot be ignored. During the experiment, sugar water and pure water will evaporate due to environmental factors such as temperature, humidity and air flow, which leads to the recorded liquid consumption being higher than the actual intake of the animals. Moreover, it is difficult to accurately estimate the evaporation volume, further increasing the uncertainty of the data.
2. Interference with animal stress responses
In traditional experiments, animals need to be frequently removed from their cages for operations such as weighing or changing water bottles. These operations can cause stress responses in animals, for instance, mice may exhibit behavioral changes such as anxiety and reduced activity. Such stress responses can affect the normal drinking behavior of animals, thereby interfering with the experimental results. Moreover, when animals are in a stressed state, their physiological functions may also change, which may lead to abnormal responses to sugar water, making the experimental data unable to truly reflect the animals’ preferences under normal conditions.
3. Lack of detail data
Conventional experiments can only provide relatively simple data, such as the total consumption of sugar water and pure water. However, more detailed data on drinking behavior, such as the duration of each drinking episode, the intervals between drinks, and changes in drinking preferences at different times of the day, cannot be obtained. These data are crucial in studying the drinking motivation of animals, their taste perception, and the precise impact of drugs on drinking behavior. The lack of such data due to traditional methods has limitation on the research.
Experimental Equipment
SANS automatic sucrose preference test uses the micro injection pump for water supply and has the advantages of real-time statistics, automation, and high accuracy. It significantly improves the efficiency of drug research and basic life science research, and fundamentally reduces data deviations and errors caused by manual operations.
Features
One channel can record 2 drinking water status at the same time.
Our software can support a maximum 200 channels SPT.
Software can automatically filter the interference of liquid volatilization on the test data.
Drinking water events can be synchronized to third-party devices through TTL signals.
Drinking time accuracy 0.01s, drinking volume accuracy 0.001ml.
Animal information: Name, Group, Age, Sex, Notes.
Modular design on drinking water detection, which is convenient for position exchange.
Support long-term test, water change during the test is available.
Natural housing cage to reduce animal stress reaction.
Separate channel operation to ensure stability of other channels.
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 sucrose 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
Sucrose 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 sucrose 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 sucrose preference index was the main evaluation index, and the criteria for judging depressive behavior were: the sucrose preference index was lower than 0.4 or significantly lower than that of the control group. The sucrose preference index of rats in the blank control group was greater than 80%, and the sucrose preference index of mice in the blank control group was greater than 70%.
There are many researchers using our Sucrose Preference Test system, and gain very good feedback.
