The evidence supporting the role of Aqp1, or aquaporin 1, in hippocampal development is less clear, however; it has been shown in Aqp-/- mutants that neuron excitability is diminished[44]; it has also been shown that Aqp1 expression is higher than normal in patients with Alzheimer’s disease (AD)[45]. This evidence concerns the gene AQP1 and early-onset autosomal dominant Alzheimer disease.