Structural and functional changes in an identified cricket neuron after separation from the soma. II. Functional...

Area of Science:

• Neuroscience
• Insect Physiology
• Cell Biology

Background:

• Understanding neuronal survival and function after axotomy is crucial for neuroscience.
• Previous studies on insect neuronal segments have shown limited physiological viability.
• The contralateral dorsal longitudinal motor neuron (CDLM) in Teleogryllus oceanicus provides a model for studying neuronal autonomy.

Purpose of the Study:

• To examine the physiological and behavioral effects of separating neuronal soma from its arborization and axon.
• To determine the functional viability of isolated neuronal segments in the Polynesian field cricket, Teleogryllus oceanicus.
• To compare the survival time of isolated cricket neuron segments with those previously described in other insects.

Main Methods:

• Surgical separation of the CDLM into proximal (soma-containing) and distal (axon and arborization) segments via midline lesions in the metathoracic ganglion.
• Isolation of axonal segments by cutting the nerve containing the CDLM axon.
• Extracellular recording of axonal conduction, electrical/tactile stimulation for pre-synaptic input, and intracellular recording for post-synaptic potentials and miniature end-plate potentials.

Main Results:

• Isolated arborization segments maintained axonal conduction, responsiveness to pre-synaptic input, and neuron-muscle transmission.
• Physiological viability of isolated cricket arborizations exceeded that of previously studied insect distal segments, with survival up to 100+ postoperative days for axonal conduction.
• Normal post-synaptic function persisted up to 44 days, limited by muscle breakdown, while the distal axon degenerated within 4 days, similar to vertebrate peripheral axons.

Conclusions:

• Isolated arborization segments of the CDLM exhibit remarkable long-term physiological viability and functional competence.
• The study highlights the extended survival capacity of distal neuronal segments in certain insect species.
• The findings provide insights into neuronal autonomy and degeneration processes, with implications for understanding nerve injury and regeneration.