Final answer:
In Aplysia, glutamate binds to G-protein-coupled receptors causing the phosphorylation and closure of potassium channels, which plays a significant role in neurotransmission and synaptic plasticity.
Step-by-step explanation:
In Aplysia, glutamate binds to a G-protein-coupled receptor which triggers a signaling cascade resulting in the phosphorylation and closure of potassium channels. This process is guided by the actions of various glutamate receptors, including NMDA and AMPA receptors. While NMDA receptors are well known for their role in synaptic plasticity due to their high calcium permeability, a subset of AMPA receptors that lack the GluA2 subunit also become permeable to calcium.
These calcium-permeable AMPA receptors are of considerable interest in the field of neurodegeneration. The process of phosphorylation leading to the closure of potassium channels, as a response to glutamate binding to receptors, is a critical part of the neurotransmission pathway that contributes to learning and memory through synaptic plasticity.