Enhanced Calcium Signaling in BLA Pyramidal Neurons Underlies a Sex and Circuit Specific Amygdala Dysfunction After Global Cerebral Ischemia

Abstract

While advances in resuscitation science have improved cardiac arrest survival, we lack therapies to improve cognitive-affective outcomes in this patient population. Our lab has previously identified cognitive dysfunction in a mouse model of global cerebral ischemia (GCI) which has been attributed to hippocampal neurodegeneration and impaired hippocampal plasticity. However, no study has attempted to identify amygdala dysfunction after GCI, despite clinical evidence of emotional dysfunction, such as anxiety and Post-Traumatic Stress Disorder (PTSD). Therefore, it is important to identify the effect that GCI has on the amygdala, the emotional center of the brain. Our lab has a well-developed, translatable mouse model of GCI, the cardiac arrest/cardiopulmonary resuscitation model (CA/CPR), that has been instrumental in assessing amygdala function after GCI. We have utilized the amygdala-dependent delay-fear conditioning (DFC) paradigm to assess associative learning and memory and have performed field excitatory post-synaptic potential (fEPSP) recordings in two circuits within the amygdala, as measures of amygdala function. We have found a sex- and circuit-specific deficit in LTP of the cortical input to the basolateral amygdala (BLA), after GCI, that corresponds with a male specific associative learning and memory deficit. We found no evidence that these deficits of amygdala function can be attributed to GCI-induced neurodegeneration within the amygdala or altered locomotor function. We did, however, find that neuronal dendritic spine calcium signaling dynamics are enhanced in male survivors of GCI and are likely contributing to the observed LTP deficit and ultimately the deficit in associative learning and memory processes. Significance StatementWhile cognitive dysfunction has been well characterized in CA/CPR survivors, the development of emotional dysfunction that may arise in survivors is understudied. Poor follow up of CA/CPR survivors has left a gap in our knowledge about the effect that GCI has on the amygdala, the emotional center of the brain. Thus, this study utilized a pre-clinical mouse model of CA/CPR to characterize amygdala dysfunction that arises from GCI. We found a male-specific deficit in associative learning and memory that corresponds with a circuit specific LTP deficit, which arises from elevated calcium signaling in dendritic spines. Thus, this study provides valuable information and rationale for extended follow up of CA/CPR survivors to identify and treat the development of GCI-induced affective disorders.