Long-term potentiation is associated with changes in synaptic ultrastructure in the rat neocortex

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Cortical Function

Background:

• Long-term potentiation (LTP) is crucial for learning and memory.
• LTP in the sensorimotor cortex involves changes in dendritic morphology and spine density.
• Previous research indicates varied synaptic alterations during LTP.

Purpose of the Study:

• To investigate synaptic number and ultrastructural changes during LTP in the rat sensorimotor cortex.
• To quantify specific synaptic features like excitatory/inhibitory contacts and synapse curvature.
• To correlate synaptic morphology changes with the degree of LTP.

Main Methods:

• Induction of LTP in the sensorimotor cortex of freely moving rats over 1 hour.
• Sacrificing animals 2 hours post-stimulation for synaptic analysis.
• Quantifying synapses in layer III pyramidal neuron dendrites, including total number, contact types, curvature, perforation, and length.

Main Results:

• No overall increase in the total number of synapses per neuron was observed.
• A significant increase in the number of excitatory perforated and concave synapses was detected.
• The quantity of perforated concave synapses correlated positively with the potentiation level.

Conclusions:

• Early-phase LTP in the sensorimotor cortex involves specific ultrastructural modifications of excitatory synapses.
• These synaptic changes resemble those seen in the hippocampus during early LTP.
• Distinct synaptic alterations may occur during later phases of LTP maintenance in different brain regions.