In behavioral neuroscience, the Elevated Plus Maze (EPM) stands as a gold-standard assay for quantifying anxiety-related behaviors in rodents. The maze’s cross-shaped structure consists of two open arms and two closed arms elevated above the ground, taking advantage of rodents’ natural aversion to open, elevated spaces. While many focus on metrics like time spent in open arms, another equally valuable yet often under-discussed variable is the Number of Entries into the Open Arms.
At Conduct Science, we emphasize that the act of entering the open arms is not randomāit reflects a conscious behavioral decision under internal stress. Every step into the exposed arm represents a tension between fear and curiosity, between aversion and exploration. Thus, measuring the frequency of these entries offers quantitative insight into the animal’s risk-taking behavior, emotional state, and response to pharmacological or genetic interventions.
Rodents typically avoid the open arms due to their anxiogenic propertiesālack of walls, height, and exposure. Therefore, the number of entries into these arms is a proxy for:
Increased entries may suggest anxiolytic effects or habituation to stress, while fewer entries may indicate anxiety, sedation, or cognitive impairment. However, entry frequency must be interpreted within context: Is the total locomotor activity also reduced? Is the animal freezing or hyperactive?
Thatās why we recommend combining this measure with:
These combined metrics offer a composite behavioral profile, far more robust than any standalone readout.
The Elevated Plus Maze system at Conduct Science is specifically engineered to maximize tracking reliability and experimental control:
Our tracking ecosystem enables not only accurate open-arm entries, but automatic classification of full versus partial entriesāa critical distinction often missed in manual scoring.
A research team investigating a novel GABA-A receptor modulator used the Conduct Science EPM system to quantify open-arm entries in male BALB/c mice.
| Group | Open Arm Entries | Closed Arm Entries | Total Distance (cm) | Time in Open Arms (s) |
|---|---|---|---|---|
|
Control (Vehicle) |
3.2 Ā± 1.1 |
9.8 Ā± 1.5 |
342.1 Ā± 32.4 |
28.4 Ā± 5.3 |
|
Low Dose (2 mg/kg) |
5.7 Ā± 1.3 |
10.5 Ā± 1.2 |
410.6 Ā± 25.8 |
54.9 Ā± 6.1 |
|
High Dose (5 mg/kg) |
7.9 Ā± 1.6 |
11.1 Ā± 1.0 |
455.3 Ā± 28.6 |
78.7 Ā± 8.2 |
Interpretation:
This demonstrates how open-arm entry frequency can serve as a sensitive, early-phase indicator of drug action, even before total time measures reveal changes.
To ensure accurate and reproducible open arm entry data:
Open arm entries may be a more relevant primary measure in:
Entry frequency can reveal willingness to explore even when the subject is not yet spending extended time in the armāa critical window into evolving behavioral state.
Ā
Time in the closed arms is not just a fallback measureāit is a core indicator of anxiety-related avoidance and behavioral inhibition. When properly interpreted, it can help distinguish between adaptive and maladaptive behavioral strategies, particularly in high-throughput screening studies and translational models.
Ā Pellow, S., Chopin, P., File, S. E., & Briley, M. (1985). Validation of open:closed arm entries in an elevated plus-maze as a measure of anxiety in the rat. Journal of Neuroscience Methods, 14(3), 149ā167.
Carobrez, A. P., & Bertoglio, L. J. (2005). Ethological and temporal analyses of anxiety-like behavior: The elevated plus-maze model 20 years on. Neuroscience & Biobehavioral Reviews, 29(8), 1193ā1205.
Rodgers, R. J., & Dalvi, A. (1997). Anxiety, defence and the elevated plus-maze. Neuroscience & Biobehavioral Reviews, 21(6), 801ā810.
Written by researchers, for researchers ā powered by Conduct Science.
Dr Louise Corscadden acts as Conduct Science’s Director of Science and Development and Academic Technology Transfer. Her background is in genetics, microbiology, neuroscience, and climate chemistry.
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