Long-term heterosynaptic inhibition in Aplysia

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Synaptic Plasticity

Background:

• Synaptic transmission in Aplysia's gill withdrawal reflex exhibits short-term and long-term modulation.
• Short-term synaptic depression, lasting minutes, is induced by Phe-Met-Arg-Phe-amide (FMRFamide) via the arachidonic acid lipoxygenase pathway.

Purpose of the Study:

• To investigate the induction of long-term synaptic depression (LTD) in the Aplysia gill withdrawal reflex.
• To determine if FMRFamide can induce LTD and compare its characteristics to short-term depression and other modulatory pathways.

Main Methods:

• Utilized Aplysia cell culture to study the monosynaptic sensory-to-motor connection.
• Applied FMRFamide repeatedly over a 2-hour period to induce long-term changes.
• Investigated the effect of anisomycin, a protein synthesis inhibitor, on FMRFamide-induced depression.

Main Results:

• Five applications of FMRFamide over 2 hours induced long-term synaptic depression lasting 24 hours.
• FMRFamide-induced LTD was transmitter-specific; dopamine and low-frequency stimulation did not induce LTD.
• Long-term depression, unlike short-term depression, was blocked by anisomycin, indicating a requirement for protein synthesis.

Conclusions:

• Long-term synaptic depression in Aplysia, similar to long-term facilitation, requires protein synthesis.
• Heterosynaptic depression, like facilitation, exists in both short-term and long-term forms, with the latter dependent on gene products.