Synaptic connectivity between cricket auditory interneurons as studied by selective photoinactivation

Area of Science:

• Neuroscience
• Animal Behavior
• Auditory System Research

Background:

• Crickets rely on sound detection and localization for survival.
• Auditory interneurons in the prothoracic ganglion are key for initial sound processing.
• Omega cells (ON/1) and ascenders (AN/2) are identified auditory interneurons in crickets.

Purpose of the Study:

• To investigate the synaptic relationship between cricket auditory interneurons, specifically ON/1 and AN/2 cells.
• To elucidate the role of ON/1 cells in mediating auditory responses.
• To understand the inhibitory connections within the cricket auditory system.

Main Methods:

• Utilized a novel photoinactivation technique for selective cell inactivation.
• Recorded and dye-marked auditory interneurons (ON/1 and AN/2) in the prothoracic ganglion.
• Stimulated cells to observe responses and analyze synaptic interactions before and after inactivation.

Main Results:

• ON/1 cells exhibit reciprocal inhibitory synaptic connections with each other.
• Contralateral stimulation of an ON/1 cell results in strong inhibition, mediated by the contralateral ON/1 cell.
• Inactivation of an ON/1 cell unmasks a weak excitatory response, indicating prior inhibition.
• AN/2 cells produce ipsilateral inhibition, which is removed upon inactivation of the ipsilateral ON/1 cell, identifying ON/1 as the inhibitory source.
• This inhibition in AN/2 is also replaced by a weak excitatory response.

Conclusions:

• ON/1 cells are reciprocally inhibitory, playing a significant role in modulating auditory input.
• ON/1 cells provide the primary source of inhibition for AN/2 cells.
• The study clarifies the intricate synaptic circuitry underlying auditory processing in crickets.