Palatable Meal Anticipation in Mice

Cynthia T Hsu,Andrew D Steele,Danica F Patton,Ralph E Mistlberger,Shin Yamazaki

doi:10.1371/journal.pone.0012903

Cynthia T Hsu, Andrew D Steele + Show 3 more

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https://doi.org/10.1371/journal.pone.0012903

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Abstract

The ability to sense time and anticipate events is a critical skill in nature. Most efforts to understand the neural and molecular mechanisms of anticipatory behavior in rodents rely on daily restricted food access, which induces a robust increase of locomotor activity in anticipation of daily meal time. Interestingly, rats also show increased activity in anticipation of a daily palatable meal even when they have an ample food supply, suggesting a role for brain reward systems in anticipatory behavior, and providing an alternate model by which to study the neurobiology of anticipation in species, such as mice, that are less well adapted to “stuff and starve” feeding schedules. To extend this model to mice, and exploit molecular genetic resources available for that species, we tested the ability of wild-type mice to anticipate a daily palatable meal. We observed that mice with free access to regular chow and limited access to highly palatable snacks of chocolate or “Fruit Crunchies” avidly consumed the snack but did not show anticipatory locomotor activity as measured by running wheels or video-based behavioral analysis. However, male mice receiving a snack of high fat chow did show increased food bin entry prior to access time and a modest increase in activity in the two hours preceding the scheduled meal. Interestingly, female mice did not show anticipation of a daily high fat meal but did show increased activity at scheduled mealtime when that meal was withdrawn. These results indicate that anticipation of a scheduled food reward in mice is behavior, diet, and gender specific.

Highlights

A near universal function of circadian clocks is to coordinate behavior and physiology with local environmental time as defined by the daily rising and setting of the sun [1]
When Group 1 mice were food deprived for 20 h, nocturnal wheel running remained elevated throughout the night and declined gradually from light onset until the first scheduled meal at ZT4 (Fig. 2a–b)
Nocturnal running reappeared on the second night, but the onset was delayed by 125691 min relative to the onset of nocturnal running during ad libitum food access (Fig. 3)

Summary

Introduction

A near universal function of circadian clocks is to coordinate behavior and physiology with local environmental time as defined by the daily rising and setting of the sun [1]. Palatable foods elicit dopamine release in the Acb [16,17,18], and if provided as a snack at a fixed time of day can induce food anticipatory activity rhythms in rats with ad libitum access to regular chow [10,19,20]. This provides an alternate model for examining the role of reward systems in anticipatory behavior, and may be more appropriate for species, such as mice, that are physiologically less tolerant of circadian feeding schedules in which mealtimes are highly compressed, or calories severely reduced

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