Cerebral-abdominal interganglionic coordinating neurons in Aplysia

Area of Science:

• Neuroscience
• Invertebrate Zoology

Background:

• Cerebral-abdominal interneurons (CAIs) play a role in coordinating nervous system functions.
• Understanding the specific roles of CAIs is crucial for deciphering neural circuits.

Purpose of the Study:

• To identify and characterize cerebral-abdominal interneurons (CAIs) in the cerebral ganglion.
• To investigate the connectivity and functional roles of CAIs in coordinating visceral and behavioral responses.

Main Methods:

• Electrophysiological recordings and immunocytochemistry were used to identify and characterize CAIs (CC2, CC3, CC7).
• Axonal tracing via the pleural-abdominal connective was performed.
• Synaptic connections to abdominal ganglion neurons and polysynaptic actions in ganglia were analyzed.

Main Results:

• Three CAIs (CC2, CC3, CC7) were identified in the cerebral ganglion C cluster, projecting to the abdominal ganglion.
• CC2 and CC3 are bilateral, CC7 is unilateral. CC3 is serotonin-immunopositive, potentially identified as CB-1.
• All CAIs respond to feeding inputs and connect to abdominal neurons controlling nonsomatic organs, with widespread polysynaptic effects.

Conclusions:

• CAIs act as crucial interneurons coordinating visceral functions controlled by the abdominal ganglion with behaviors like feeding and head withdrawal regulated by head ganglia.
• The identified CAIs provide insights into the neural mechanisms underlying the integration of visceral and somatic behaviors.