Localization of spinal neurons activated during locomotion using the c-fos immunohistochemical method

Area of Science:

• Neuroscience
• Spinal Cord Research
• Motor Control

Background:

• Understanding the neural circuits controlling locomotion is crucial for treating movement disorders.
• The c-fos immunohistochemical method allows for the identification of activity-dependent neuronal populations.

Purpose of the Study:

• To localize neurons activated during locomotion in the adult cat spinal cord using c-fos expression.
• To differentiate between neurons involved in motor command generation and those responding to sensory feedback.

Main Methods:

• Utilized decerebrate cats with treadmill locomotion evoked by mesencephalic locomotor region (MLR) stimulation.
• Employed c-fos immunohistochemistry to label activated neurons in L3-S1 spinal cord segments.
• Compared labeling patterns between treadmill locomotion, fictive locomotion, and control conditions.

Main Results:

• Locomotion activated neurons in dorsal horn laminae III and IV, and intermediate/ventral horn laminae VII, VIII, and X.
• Fictive locomotion primarily labeled neurons in laminae VII, VIII, and X, with reduced dorsal horn labeling.
• c-fos labeling was significantly higher in locomotor animals compared to controls, with peak expression in L5-L7 segments.

Conclusions:

• Neurons in laminae VII, VIII, and X are likely premotor interneurons essential for locomotion production.
• Neurons in dorsal horn laminae III and IV are activated by afferent feedback from the moving limb.
• The distribution of c-fos labeled cells aligns with known distributions of locomotor-activated neurons.