Hippocampal Estrogen Signaling Mediates Sex Differences in Retroactive Interference

Area of Science:

• Neuroscience
• Molecular Biology
• Endocrinology

Background:

• Forgetting mechanisms remain poorly understood, despite its importance in brain function.
• Estrogens are vital for brain functions, including memory, but their role in forgetting vulnerability is unclear.
• Retroactive interference (RI) is a form of forgetting where new information impairs recall of older information.

Purpose of the Study:

• To investigate sex differences in forgetting mediated by retroactive interference.
• To identify the molecular mechanisms underlying these sex differences in forgetting.
• To explore the role of estrogen signaling and hippocampal pathways in memory retention.

Main Methods:

• Utilized the Novel Object Recognition (NOR) paradigm to assess memory and forgetting in male and female mice.
• Investigated the role of estrogen receptor alpha (ERα) and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in the hippocampus.
• Administered PD98059, an ERK1/2 inhibitor, to assess its effect on RI-dependent memory loss in females.

Main Results:

• Male mice exhibited greater susceptibility to RI-dependent memory loss compared to females (PI: 52.7% vs. 62.3%).
• Estrogen signaling via ERα in the dorsal hippocampus mediated resistance to RI in females.
• Females showed higher hippocampal ERK1/2 phosphorylation post-RI, and its inhibition (PD98059) increased forgetting in females.

Conclusions:

• Hippocampal estrogen α receptor-ERK1/2 signaling is crucial for inhibiting retroactive interference in female mice.
• This pathway is involved in pattern separation, a mechanism that protects memories from new interfering information.
• Sex differences in memory consolidation and forgetting are influenced by hormonal and molecular mechanisms in the brain.