Entorhinal Cortex Circuit Dysfunction in Mouse Models of APOE4 and Chemotherapy‐Induced Cognitive Impairment

Abstract

AbstractBackground APOE4 has broad effects, one of which is worsened cognitive outcomes in cancer survivors following chemotherapy treatment compared to APOE3.Method1‐2 month old female APOE3 and APOE4‐Targeted Replacement (TR) mice were used for whole cell patch‐clamp experiments in the entorhinal cortex. Chemotherapy was introduced via a single injection of doxorubicin (10 mg/kg) or saline (control) and treated APOE‐TR mice were euthanized 1 week post‐injection. 0.5% biocytin internal solution was used to visualize cell morphology post hoc under a confocal microscope.ResultsPyramidal cells in the entorhinal cortex of APOE4‐TR mice (4 mice, n = 26 cells) exhibit significantly decreased spontaneous excitatory and inhibitory postsynaptic current frequencies, thereby contributing to an elevated excitatory‐inhibitory balance compared to APOE3‐TR mice (4 mice, n = 23 cells). Doxorubicin‐treated APOE3‐TR mice (4 mice, n = 33 cells) show a significant increase in spontaneous excitatory and inhibitory postsynaptic current amplitudes compared to controls (2 mice, n = 16 cells), while doxorubicin‐treated APOE4‐TR mice (5 mice, n = 20 cells) display no such synaptic changes compared to controls (4 mice, n = 19 cells).Conclusion APOE4 has baseline effects on entorhinal cortex circuit inhibition and the lack of response to chemotherapy may reflect reduced resilience to stressors.