What is the primary action of Memantine in the treatment of Alzheimer’s disease?

Memantine primarily acts by blocking NMDA (N-methyl-D-aspartate) receptors in the brain. This mechanism is significant in the treatment of Alzheimer's disease as it helps to regulate the neurotransmitter glutamate, which plays a crucial role in learning and memory. In Alzheimer's patients, excessive activation of NMDA receptors by glutamate can lead to increased excitotoxicity and neuronal damage. By blocking these receptors, Memantine mitigates this harmful overactivity, thus providing a protective effect on nerve cells and potentially slowing the progression of cognitive decline associated with the disease.

Other options relate to different mechanisms that do not align with Memantine's therapeutic actions. For instance, increasing acetylcholine pertains to other medications used in Alzheimer's treatment but not to Memantine. Similarly, inhibiting serotonin reuptake is a mechanism associated with antidepressants. Allowing greater dopamine release is more relevant in the context of Parkinson's disease rather than Alzheimer's. Each of these mechanisms targets different pathways within the brain, making them ineffective in the context of Memantine’s role in managing Alzheimer's disease.