Neuroscience

The neuromuscular junction (NMJ) is critical for muscle function, and its dysfunction underlies conditions such as sarcopenia and motor neuron diseases. Current protocols for assessing NMJ function often lack standardized stimulation parameters, limiting reproducibility. This study presents an optimized ex vivo method to evaluate skeletal muscle and NMJ function using the Aurora Scientific system, incorporating validated stimulation protocols for both nerve and muscle to ensure consistency. Key steps include tissue preparation in a low-calcium, high-magnesium solution to preserve NMJ integrity, determination of optimal muscle length, and sequential stimulation protocols to quantify neurotransmission failure and intratetanic fatigue. By integrating rigorous standardization, this approach enhances reproducibility and precision, providing a robust framework for investigating NMJ pathophysiology in aging and disease models.

Changes in neuronal conduction are common in disease states affecting peripheral nerves. These alterations can significantly impact nerve function and lead to sensorimotor disabilities. In vivo electromyography recording is a well-established electrophysiological method that has been used for decades to assess sensory and motor functions in the nervous system. Nerve studies are challenging to conduct in vivo in rodents, and the involvement of muscle activity makes it difficult to isolate and assess nerve function independently. This protocol provides a comprehensive guide for accurate ex vivo sciatic nerve dissection and handling from mice. It includes the creation of a three-compartment chamber and the establishment of electrophysiological protocols, which enable differential recordings and the analysis of compound action potentials from various nerve fibers. This setup allows researchers to study the specific effects of drugs and pathologies on nerves from a mechanistic perspective. The setup is a stand-alone apparatus that does not require the use of suction electrodes and the maintenance of negative pressure, which can affect the signal-to-noise ratio and recording stability.

Enhancing axon regeneration is a major focus of peripheral nerve injury research. Although peripheral axons possess a limited ability to regenerate, their functional recovery is very poor. Various activity-based therapies like exercise, optical stimulation, and electrical stimulation as well as pharmacologic treatments can enhance spontaneous axon regeneration. In this protocol, we use a custom-built cuff to electrically stimulate the whole sciatic nerve for an hour prior to transection and repair. We used a Thy-1-YFP-H mouse to visualize regenerating axon profiles. We compared the regeneration of axons from nerves that were electrically stimulated to nerves that were not stimulated (untreated). Electrically stimulated nerves had longer axon growth than the untreated nerves. We detail how variations of this method can be used to measure acute axon growth.