This is the first study that characterizes the motor end plate (MEP) region for the rat hindlimb.

The MEP regions traverse the entire width of a muscle and are arranged orthogonal to the muscle fiber orientation.

Targeting the MEP region with Fluoro-Gold leads to robust and maximal labeling of the innervating motor neurons.

Motor neurons innervating targeted hindlimb muscles span multiple segments of the lumbosacral spinal cord.

This study has implications for the intramuscular delivery of viral-vectors for the treatment of spinal cord injury.