Intramuscular Injections Along the Motor End Plates to Shuttle Tracers Directly into Rat Motor Neurons

Take an anesthetized rat and apply eye lubricant.

Shave the targeted limb, sterilize the skin, and position the rat to ensure optimal access to the targeted muscle.

Lift and incise the skin to expose the muscle.

Refer to photographs of motor end plates or MEPs, the regions where motor neuron axon terminals synapse with muscle fibers to form neuromuscular junctions.

Mentally map the MEP region onto the exposed muscle.

Take a glass micropipette containing a fluorescent tracer.

Inject the tracer intramuscularly at multiple points along the MEP region.

Remove any excess tracer, close the incision, and administer a pain suppressant.

The injection enhances tracer availability at neuromuscular junctions, facilitating its endocytosis at axon terminals.

The tracers enclosed within vesicles are then transported retrogradely to motor neuron cell bodies in the spinal cord.

The presence of tracer-labeled motor neurons in the spinal cord suggests the neurotherapeutic potential of MEP-targeted delivery.

To inject the live muscle at the motor end plates, first use a micropipette puller to pull graded glass micropipettes equipped with plungers. Next, using a dissecting microscope, break the tips of the micro