Magnetic resonance elastography captures subtle changes in hippocampal CA1 stiffness between phases of the rat estrous cycle

Motivation: In rodent studies, the number of spines on hippocampal CA1 neurons decreases from proestrus to estrus, and complimentary reductions to hippocampal volume are observed in rodents and humans. It remains unknown if estrous-related changes to tissue microstructure alter the mechanical properties of CA1. Goal(s): Evaluate the mechanical properties of CA1 between proestrus and estrus in the adult rat brain. Approach: A novel rat Magnetic Resonance Elastography (MRE) protocol, measuring tissue deformation to determine stiffness and viscosity, was used to identify changes to the mechanical properties of CA1. Results: CA1 stiffness increases between proestrus and estrus phases in female rats. Impact: Results from this longitudinal study show that the stiffness of the hippocampal CA1 subregion increases between proestrus and estrus phases within-rat. We did not discover any changes to whole brain biomechanics between proestrus and estrus within-rat, consistent with the literature.