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Updated: Mar 17, 2026
Elevated Plus Maze for Mice
Published on: December 22, 2008
Effects of Different Levels of Protein and Environmental Stimulation on the Behavior of Young Rats Tested in the
T R Riul1, P S Almeida1, A F Carvalho1
1a Laboratory of Nutrition and Behavior , FFCLRP-USP , Avenida Bandeirantes, 3900, 14040-901, Ribeirão Preto- SP , Brazil.
Insights
Environmental stimulation reduces anxiety in young rats, while severe protein deficiency (6%) also alters emotional responses. Moderate protein deficiency (10%) did not significantly impact behavior in the elevated plus-maze.
Area of Science:
- Neuroscience
- Behavioral Science
- Nutritional Science
Background:
- Early life nutrition and environmental factors significantly influence neurodevelopment and behavior.
- The elevated plus-maze (EPM) is a standard behavioral paradigm for assessing anxiety-like behaviors in rodents.
- Understanding the interplay between malnutrition and environmental enrichment is crucial for identifying critical developmental periods and interventions.
Purpose of the Study:
- To investigate the combined effects of varying protein malnutrition levels and environmental stimulation on anxiety-like behavior in young male rats.
- To determine the impact of early-life handling and dietary protein content on emotional reactivity using the elevated plus-maze.
- To assess age-related changes in anxiety and the influence of nutritional status on these changes.
Main Methods:
- Male rat pups were fed diets with 16% (control), 10%, or 6% protein.
- Half of the litters received daily handling (environmental stimulation) from postnatal day 1 to 22.
- Behavioral testing in the elevated plus-maze was conducted at 22 and 35 days of age, with some rats switched to a standard diet post-weaning.
Main Results:
- Environmental stimulation (handling) significantly increased open arm exploration, indicating an anxiolytic effect.
- Anxiety-like behavior increased with age, as evidenced by reduced open arm exploration in 35-day-old rats compared to 22-day-old rats.
- Severe protein malnutrition (6% protein) led to increased open arm entries and decreased attempts to enter open arms, suggesting altered emotional responses, while 10% protein malnutrition did not cause significant behavioral changes.
Conclusions:
- Early-life environmental stimulation exerts anxiolytic effects in young male rats.
- Protein deficiency as severe as 6% can induce behavioral alterations in the elevated plus-maze, indicating emotional response changes.
- Dietary protein levels below 10% are necessary to elicit significant behavioral modifications in the elevated plus-maze test during early development.
Unlabelled:
The interaction between the effects of different levels of protein malnutrition and environmental stimulation was investigated in young male rats in the elevated plus-maze (EPM). Litters (dam plus 6 male and 2 female pups) were fed a 16% (
Control:
C), 10% (Malnourished: M10) or 6% (Malnourished: M6) protein diet. Half of the litters were daily exposed to additional stimulation (CS, MS10 or MS6), while the other half was maintained in normal rearing conditions (CN, MN10 or MN6). The stimulation (handling) consisted of holding the rat in one hand and gently touching the dorsal part of the body with the fingers for 3 min. On the 22nd day of life (weaning), two male pups from each group were tested in the plus-maze. Two male pups continued to receive the same diet as their mothers, and the other two were fed a non-purified lab chow diet until 35 days of age when they were tested in the plus-maze (LN, LS, LN10, LS10, LN6 and LS6 groups). Results showed that environmental stimulation increased open arms exploration both at 22 and 35 days of age, indicating an anxiolytic effect of this procedure. Younger rats (22 days of age) explored significantly more the open arms of the maze as compared with older rats (35 days of age), indicating an increase in anxiety with age. M6 animals showed significantly higher percentages of open arm entries and less frequent attempts to enter open arms in the maze as compared with C and M10 animals. These results suggest that even a short period of protein deficiency can produce alterations in the emotional response of rats in the elevated plus-maze. In addition, the data demonstrated that protein deficiency more severe than 10% is necessary to produce behavior alterations in the EPM test.
