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
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Protocol Steps
Housing preparation
House SHR/Izm rats individually in specified cages with minimal sawdust for 5 weeks from P25 to P60
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“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
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“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
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“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
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“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
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“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)
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“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
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“Each aggression category was analyzed for frequency, duration, and latency over a 10-minute observation period”