Maternal aggression: new insights from Egr-1

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Molecular Neuroscience

Background:

• Lactating female mice exhibit pronounced aggression towards intruders.
• Understanding the neural basis of maternal aggression is crucial for comprehending complex social behaviors.

Purpose of the Study:

• To investigate and compare neuronal activity in aggression-tested versus untested lactating mice.
• To identify specific brain regions involved in regulating maternal aggression using early growth response factor 1 (Egr-1) as a marker.

Main Methods:

• Neuronal activity was assessed by measuring Egr-1 immunoreactivity (Egr-IR) in brain tissue.
• Mice were sampled 90 minutes after a 7-minute interaction with a male intruder.
• Immunoreactivity was quantified in 40 distinct brain regions, including novel examination of the medial amygdala subregions.

Main Results:

• Aggression-tested mice showed significantly increased Egr-IR in 11 of 40 brain regions compared to untested mice.
• Key areas with elevated Egr-IR included the paraventricular nucleus of the hypothalamus, hypothalamus subdivisions, periaqueductal gray, and amygdala.
• The posterodorsal medial amygdala (MePD), a region linked to aggressive behaviors, exhibited increased Egr-IR following testing.

Conclusions:

• The study reveals specific neural circuits activated during maternal aggression in lactating mice.
• Increased Egr-1 expression in regions like the amygdala and hypothalamus is associated with the expression of maternal defensive behaviors.
• These findings offer novel insights into the neurobiological underpinnings of maternal aggression.