Source Paper
The intake of monosodium aspartate attenuates aggression induced by post-weaning social isolation in an ADHD rat model
Nishimura Y, Mustika D, Ueno S, Tominaga S, Shindo M et al.
J Physiol Sci • 2026
Resident Intruder Test
Objective: To evaluate aggression in SHR/Izm rats using a resident-intruder paradigm
This is a Resident Intruder Test protocol using Rat as the model organism. The procedure involves 7 procedural steps, 2 equipment items, 3 materials. Extracted from a 2026 paper published in J Physiol Sci.
Model and subjects
Rat • SHR/Izm (residents) and Wistar/ST (intruders) • Male • P60 (residents), intruders approximately 20g lighter • 12
Study window
~5 week study window | ~10 minutes hands-on
Core workflow
Housing preparation • Intruder introduction • Testing conditions
Primary readouts
- Frequency of aggressive behaviors
- Duration of aggressive behaviors
- Latency to aggressive behaviors
- Anogenital sniffing (weak aggression)
Key equipment and reagents
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Protocol Steps
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Housing preparation
House SHR/Izm rats individually in specified cages with minimal sawdust for 5 weeks from P25 to P60
View evidence from paper
“individually housed in cages measuring 40 × 23 × 18 cm, with minimal sawdust, from post-weaning at P25 until reaching maturity at P60”
Intruder introduction
Introduce a male Wistar/ST rat approximately 20g lighter than the resident into the resident's home cage
View evidence from paper
“A male Wistar/ST rat, approximately 20 g lighter than the resident, was introduced into the resident's home cage and designated as the intruder”
Testing conditions
Conduct test during dark phase between 13:00 and 16:00 under dim red light
View evidence from paper
“Behavioral recordings were performed under dim red light (<2 lx) between 13:00 and 16:00”
Multi-day testing
Conduct test over three consecutive days using the same resident-intruder pair
View evidence from paper
“The test was conducted over three consecutive days using the same resident-intruder pair to ensure consistency”
Behavioral observation
Record and analyze aggressive behaviors for 10 minutes, focusing on data from the second day
View evidence from paper
“Behavioral data from the second day were analyzed, as aggression levels were more stable at this time point”
Behavior categorization
Classify aggressive behaviors into three categories: anogenital sniffing (weak), allo-grooming (moderate), and attack (strong)
View evidence from paper
“Aggressive behaviors were classified into three categories based on previously established criteria: anogenital sniffing (weak aggression), allo-grooming (moderate aggression), characterized by mounting and pouncing, and attack (strong aggression)”
Data analysis
Analyze each aggression category for frequency, duration, and latency over the 10-minute observation period
View evidence from paper
“Each aggression category was analyzed for frequency, duration, and latency over a 10-minute observation period”