Which is the most likely reason the hippocampus is more vulnerable to neuronal death during global ischemia?

• A. Higher action potential magnitudes in hippocampal neurons
• B. More NMDA receptors present in hippocampal neurons
• C. More negative postsynaptic potentials in hippocampal neurons
• D. Faster neurotransmitter diffusion in hippocampal synapses

Answer: (B)

The hippocampus is particularly vulnerable to neuronal death during global ischemia primarily because it has a higher concentration of NMDA (N-methyl-D-aspartate) receptors. NMDA receptors are a type of glutamate receptor that, when activated, allow calcium ions to flow into the neuron. During ischemic events, there is a lack of oxygen and glucose which affects cellular metabolism and leads to an imbalance in neurotransmitter levels. The excessive release of glutamate, combined with the heightened presence of NMDA receptors in the hippocampus, results in excessive calcium influx. This overload can trigger a series of intracellular processes that ultimately lead to neuronal death, highlighting the critical vulnerability of the hippocampus in ischemic conditions.

In contrast, the other options do not directly account for the heightened vulnerability of the hippocampus during global ischemia. For instance, the first option regarding action potential magnitudes does not specifically relate to the mechanisms of damage during ischemia. Negative postsynaptic potentials or faster neurotransmitter diffusion would not contribute to the elevated risk of neuronal death in the same direct manner as the overactivation of NMDA receptors does during periods of glutamate excitotoxicity. Thus, the presence of more NMDA receptors is the most significant factor contributing to the hippocampus