The sucrose preference test is a simple task that is used to assess motivation, depression (and anhedonia) and related emotional states in rodent models. It has been used for more complex models as well, such as postpartum depression and drug withdrawal. In short, animals are presented with two drinking solutions, either in their home cage or in an experimental apparatus. One solution is sweetened with sucrose (or occasionally, other sweeteners), while the other is plain drinking water. Animals exhibit a preference for one solution over the other, as measured by total liquid intake.
Disorders of reward behavior lead to a reduced preference for the sweetened solution, indicated by lower consumption. In this vein, reduced sucrose preference has been shown to correlate with a number of other measures of depression, such as learned helplessness and the light/dark box. As an important measure of model validity, following anhedonia-induction (for instance by chronic mild stress) and the subsequent loss of sucrose preference, behavioral parameter rescue by antidepressant drugs is accompanied by a restoration of sucrose preference.[5-6] Thus, the sucrose preference test provides a simple and reliable measure of depression and associated anhedonia in rodents that requires minimal manipulations and equipment.
Procedures and Notes
To properly employ the sucrose preference test, animals are presented with two identical drinking bottles, one of which is sweetened with sucrose. The common concentration for sucrose is between 1-2% dissolved in either distilled water or standard drinking water. The positioning of the two bottles should be regularly alternated in order to eliminate the possibility of a side- or place-preference.
Sucrose preference may be measured during an entire day or during a selected period of time. If using a selected time period, it is important to do so consistently across animals, as nocturnal rhythms impact preference behavior. Outcome measurements can be calculated in several fashions, including total milliliters of solution consumed (a ratio of sweetened to unsweetened) or grams of sucrose consumed per gram of body weight. While these two measurements are normally correlated in animal models, the latter of these measurements may provide further insight into disorder eating behavior or weight loss associated with stress and anxiety.
Importantly, mice or rats must be in single-housed conditions (i.e. in individual cages) for the sucrose preference test to provide accurate measurements. A distinction between individual animal preferences can otherwise not be made. This individual housing procedure normally requires 48-72 hours of adaptation if the animals were previously housed in groups.
Some researchers have suggested that due to its caloric content, sucrose is not the best choice of sweetener for this task, as it indicates a preference for a caloric liquid over a non-caloric liquid, rather than a pleasurable versus neutral stimulus. While this has been contradicted by evidence such as observations of no-difference between food-deprived and non-deprived rats. non-caloric sweeteners are still often used to control for this variable. Alternatives to sucrose as a sweetener include a saccharin solution (normally at 0.1%, considering its relatively concentrated sweetness as compared to sucrose) for which no differences in consumption have been noted in both naïve animals and models of depression such as chronic mild stress.
As with many experimental procedures, some differences are noted between strains of mice and rats with regards to sucrose preference. For instance, Lister hooded rats exhibit a significant sucrose preference at a concentration of 1%, while Wistar rats do not. In this case, the concentration of sucrose must be increased to 2% for the less sensitive Wistar rats Similarly, mouse strains exist which exhibit comparatively low levels of sensitivity to sucrose. For instance, as compared to the oft-used C57BL/6J mice, 129P3/J mice show a lower preference for sucrose- or maltodextrin-sweetened solutions.
In addition to strain-differences, some researchers have noticed rodent sex-differences in sucrose preference. For instance, while male Wistar Kyoto rats exhibit lower sucrose-preference than their female counterparts, no such difference exists in Sprague-Dawley rats who show equal levels of sucrose preference between the sexes. Interestingly, this sex-difference carries over to stress-induced reductions in sucrose preference. Kyoto Wistar male rats exhibit a stress-induced loss of sucrose preference while females do not; on the contrary, both male and female Sprague Dawley rats show a reduction in sucrose preference following chronic mild stress.
Sucrose preference testing provides a reliable measure of anhedonia in rodents in a variety of behavioral models. As this protocol may be performed in the home cage, does not require pre-training and uses relatively minimal materials, it is an attractive measurement for researchers looking to validate their models of depression or stress. Important considerations for researchers performing the sucrose preference test include strain and sex differences as well as indications of outcome measurements, as described above.
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- Fernandez, J. W., Grizzell, J. A., Philpot, R. M., & Wecker, L. (2014). Postpartum depression in rats: Differences in swim test immobility, sucrose preference and nurturing behaviors. Behavioural Brain Research, 272, 75–82.
- Alkhlaif, Y., Bagdas, D., Jackson, A., Park, A. J., & Damaj, M. I. (2017). Assessment of nicotine withdrawal-induced changes in sucrose preference in mice. Pharmacology, Biochemistry, and Behavior, 161, 47–52.
- Sanchi-Segura. C., Spanagel R., Henn, F.A., Vollmayr, G. (2005) Reduced sensitivity to sucrose in rats bred for helplessness: a study using the matching law. Behav. Pharmacol. 16, 267–270.
- Liu, X. L. et al. Fluoxetine regulates mTOR signalling in a region-dependent manner in depression-like mice. Sci. Rep. 5, 16024 (2015).
- Willner, P., Towell, A., Sampson, D., Sophokleous, S., & Muscat, R. (1987). Reduction of sucrose preference by chronic unpredictable mild stress, and its restoration by a tricyclic antidepressant. Psychopharmacology, 93(3), 358–364.
- Eagle, A., Mazei-Robison, M., & Robison, A. (2016). Sucrose Preference Test to Measure Stress-induced Anhedonia. BIO-PROTOCOL, 6(11).Liu, M.-Y., Yin, C.-Y., Zhu, L.-J., Zhu, X.-H., Xu, C., Luo, C.-X., … Zhou, Q.-G. (2018). Sucrose preference test for measurement of stress-induced anhedonia in mice. Nature Protocols, 13(7), 1686–1698.
- Muscat, R., & Willner, P. (1992). Suppression of sucrose drinking by chronic mild unpredictable stress: a methodological analysis. Neuroscience and Biobehavioral Reviews, 16(4), 507–517.
- Willner, P. (1997). Validity, reliability and utility of the chronic mild stress model of depression: a 10-year review and evaluation. Psychopharmacology, 134(4), 319–329
- Ackroff, K., & Sclafani, A. (2016). Maltodextrin and Sucrose Preferences in Sweet-Sensitive (C57BL/6J) and Subsensitive (129P3/J) Mice Revisited. Physiology & Behavior, 165, 286–290
- Burke, N. N., Coppinger, J., Deaver, D. R., Roche, M., Finn, D. P., & Kelly, J. (2016). Sex differences and similarities in depressive- and anxiety-like behaviour in the Wistar-Kyoto rat. Physiology & Behavior, 167, 28–34.