Final answer:
The late phase of LTP involves a CaMKII-dependent cascade initiated by calcium entry through NMDA receptors, leading to the insertion of AMPA receptors and strengthening the synaptic connection.
Step-by-step explanation:
The late phase of LTP implementation, which is crucial for synaptic strengthening, involves the calcium- and CaMKII-dependent signaling cascade. After the NMDA receptors expel magnesium ions upon strong depolarization, calcium ions (Ca²⁺) can enter the postsynaptic neuron. This influx of calcium ions initiates a series of events that ultimately lead to the insertion of additional AMPA receptors into the postsynaptic membrane. The presence of more AMPA receptors at the synapse means an increased response to subsequent glutamate release from the presynaptic neuron, enhancing the synaptic connection and facilitating learning and memory.
This process may also involve a second messenger cascade and gene transcription that result in the synthesis of more protein kinases like CaMKII and PKAII. These changes occur at a highly localized level, confined to the individual synaptic spine, thereby providing a precise mechanism for altering synaptic strength in a space- and time-dependent manner. The role of LTP in addiction is also acknowledged, given that certain drugs of abuse can exploit these synaptic mechanisms, enhancing their addictive potential.