Dorsal horn neurons having input from low back structures in rats

Area of Science:

• Neuroscience
• Pain Research
• Spinal Cord Research

Background:

• Nociception mechanisms in the low back are poorly understood.
• Systematic recordings from dorsal horn neurons receiving low back input are lacking.
• This limits understanding of low back pain pathophysiology.

Purpose of the Study:

• Identify spinal segments and dorsal horn neurons receiving low back input.
• Assess the effect of nerve growth factor (NGF) on multifidus muscle (MF) neurons.
• Investigate the impact of chronic MF inflammation on neuronal responses.

Main Methods:

• Used microelectrode recordings in rat spinal segments L2, L3, and L5.
• Identified low back (LB) neurons and their input convergence.
• Administered NGF and induced chronic inflammation in the MF.

Main Results:

• LB neurons were more prevalent in L2 compared to L3 and L5 in controls.
• NGF injection and chronic MF inflammation significantly increased LB neuron proportion.
• Input convergence from multiple tissues was common in LB neurons.
• Neuronal receptive fields were located 2-3 segments caudally to the recording site.

Conclusions:

• Low back neurons exhibit input convergence from various tissues.
• Low back input is processed cranially relative to receptive field vertebral level.
• Pathological changes in the multifidus muscle increase LB neuron responsiveness.
• Findings may be relevant for understanding chronic low back pain in patients.