Three-chamber social approach

Phenotype: Social Preference

Animals: 

  Test mouse: 8–14-week-old WT C57BL/6J mice 

• bred in house or ordered at 3 weeks old

  Cupped mouse: Sex- and strain-matched younger mouse

• No bedding under cup as used in Heifets et al 2019

Temperature: 21–24 °C

Lighting: Dim, indirect light in three chamber apparatus

Sample size: 8 per group (cross over design yields n=16 per group)

Habituation: 

• 60-minute habituation in test room before handling
• 1 day prior to testing, allow each test mouse to individually roam the three-chamber apparatus with empty cups for 10 minutes

Test day:

• 60-minute habituation in test room before handling
• For each cage of mice, inject saline or drug in the home cage, wait 10 minutes.
• Place cupped mouse under one cup, leaving the other cup empty
• Place one injected mouse in each three-chamber apparatus, after a 2 minute habituation, withdraw dividing walls, and record activity with an overhead camera for 30 minutes

Crossing over:

• Allow 1 week between injections
• Habituate mice to test chamber again 1 day before testing
• Treatments are reversed from week prior

Cleaning:

• Between experimental sessions, clean cups, and the floor of the three-chamber apparatus to minimize the effect of residual scent cues on behavioral testing.

Data analysis:

• Quantify velocity and distance traveled over 30 minute test period 
• For the last 10 minutes of the 30-minute test period, calculate the sociability index for each test mouse
  • Sociability index = 100 × (cup mouse time − cup time) / (cup mouse time + cup time)

Expected results:

• No inherent social preference under saline condition
• Sociability index for 7.5 mg/kg (±)-MDMA ~30%