Disturbed emotionality in autoimmune MRL-lpr mice

Area of Science:

• Neuroscience
• Immunology
• Behavioral Science

Background:

• MRL-lpr mice spontaneously develop autoimmune lupus-like disease earlier than MRL +/+ mice.
• Previous research suggests autoimmune MRL-lpr mice display altered emotional reactivity.

Purpose of the Study:

• To investigate the hypothesis that autoimmune MRL-lpr mice exhibit altered emotional reactivity.
• To identify behavioral measures that effectively differentiate MRL-lpr mice from MRL +/+ controls.

Main Methods:

• Comparison of male MRL-lpr and MRL +/+ mice (n=40/substrain, 3-4 months old) using a battery of behavioral tests.
• Tests included open field, elevated platform, novel object interaction, plus-maze, and Porsolt's swim test.
• Discriminant analysis was employed to identify key behavioral differences.

Main Results:

• MRL-lpr mice showed reduced exploration in the open field, increased time spent at home-base, and less defecation compared to MRL +/+ mice.
• MRL-lpr mice exhibited hesitation on an elevated platform, avoided novel objects, and spent less time on open arms of the plus-maze.
• Porsolt's swim test and the step-down test most effectively distinguished between the two substrains.
• In MRL-lpr mice, high antinuclear antibody titers correlated with impaired novel object exploration.

Conclusions:

• Results support the notion of increased timidity in autoimmune MRL-lpr mice, suggesting an immune system contribution to emotional reactivity.
• The observed behavioral disturbances in autoimmune MRL-lpr mice resemble those of stressed animals.
• It is speculated that altered emotional reactivity reflects autoimmunity's impact on the hypothalamic-pituitary-adrenal axis.