As described above, there are proteins at all levels in the second messenger signaling cascade that work in concert to stimulate PI turnover. Importantly, if expression of any of these proteins was decreased in the aged brain, the result could significantly contribute to deficient neuronal communication and, ultimately, impaired learning and memory processes. Thus, the quantification of the availability of key proteins involved in the second messenger signal transduction cascade is an essential first step in investigating this signaling pathway as a causative factor in age-related cognitive decline. The critical machinery includes the G-protein receptor, G-protein subunits, and downstream enzymes and precursor molecules necessary for transduction. Neurotransmitter receptor and downstream effector levels can both be examined using Western blotting techniques in hippocampal tissue homogenates. Receptor binding can also be assayed in a more regionally specific manner using hippocampal slices.
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