A gene - ApoE - has been linked to increased risk of Alzheimer's. Carrying certain alleles of this gene increase the risk of Alzheimer's. However, it is not clear if this is due to a role for ApoE in the brain, or due to how this allele of ApoE also seems to be correlated with high blood pressure. How - using animal models, not humans - would you go about testing if high blood pressure causes damage to the hippocampus? How could you test if high blood pressure is sufficient to damage the hippocampus? How could you test if it is necessary?