Effects of under- and overcrowding on exploratory behavior in the elevated plus-maze

Area of Science:

• Animal Behavior
• Neuroscience
• Laboratory Animal Science

Background:

• The elevated plus-maze is a standard tool for assessing anxiety-like behavior in rodents.
• Standardized housing conditions are crucial for reliable and reproducible behavioral research.

Purpose of the Study:

• To determine the effect of varying rat densities within cages on exploration of the elevated plus-maze.
• To investigate potential anxiogenic effects associated with undercrowding and overcrowding in laboratory rats.

Main Methods:

• Male Wistar-derived rats were housed in cages at densities ranging from 1 to 24 rats per cage.
• Animals were housed for either 1 or 14 days before testing in the elevated plus-maze.
• Exploration was quantified by measuring entries and time spent in the open arms of the maze.

Main Results:

• Rats housed at extreme densities (1, 2, 16, or 24 per cage) for 1 day showed reduced open arm exploration compared to controls (6 rats/cage).
• Similar reductions in open arm exploration were observed in rats housed at extreme densities for 14 days.
• Housing densities between 4 and 12 rats per cage did not significantly alter plus-maze exploration.

Conclusions:

• Both undercrowding and overcrowding can induce anxiogenic effects in rats, impacting their behavior in anxiety tests.
• These findings highlight the importance of considering cage density as a critical variable in rodent behavioral research.
• Careful attention to housing conditions is necessary to ensure the validity of animal models in neuroscience and behavioral studies.