Composite modulatory feedforward loop contributes to the establishment of a network state.

Area of Science:

• Neuroscience
• Systems Neuroscience
• Computational Neuroscience

Background:

• Feedforward loops (FFLs) are network motifs with unclear roles in neural circuits.
• The Aplysia feeding central pattern generator (CPG) controls ingestive and egestive behaviors.
• The esophageal nerve (EN) input activates a modulatory element (B65) to promote egestion.

Purpose of the Study:

• To investigate the role of small cardioactive peptide (SCP) in the Aplysia feeding network.
• To elucidate how FFLs contribute to establishing specific network states.

Main Methods:

• Immunostaining and mass spectrometry to detect SCP in the EN.
• Electrophysiological recordings to assess SCP's effects on interneurons.
• Analysis of FFLs in the context of ingestive and egestive motor programs.

Main Results:

• SCP is present in the EN and released upon stimulation.
• SCP directly modulates B20 and B40 interneurons, promoting egestion and suppressing ingestion.
• SCP enhances B65 activity, contributing to the egestive state.
• Two FFLs, one promoting egestion and one suppressing ingestion, were identified.

Conclusions:

• A composite FFL involving SCP, B65, B20, and B40 interneurons co-regulates competing neural elements.
• This FFL mechanism effectively establishes specific network states in the Aplysia feeding CPG.