Thalamic activation in a disc herniation model.

• STUDY DESIGN: A novel approach combining a rodent disc herniation model with electrophysiologic recordings of thalamic evoked responses. OBJECTIVE: To assess short-term effects of nucleus pulposus (NP) application on dorsal root ganglions (DRG) on high threshold afferent fiber evoked activation in the thalamus. SUMMARY OF BACKGROUND DATA: Epidural application of NP in combination with mechanical compression induces pain related behavior in rats associated with enhanced activity of pain-processing neurons in the dorsal horn of the spinal cord. However, possible effects on neuronal activity in the pain processing ventral posterior lateral (VPL) thalamic nucleus following NP application on DRG have not been investigated. METHODS: Responses in the contralateral VPL evoked by electrical stimulation of the sciatic nerve and of the fourth lumbar (L4) DRG were recorded in adult Sprague-Dawley rats. Records were obtained before and during application (5, 10, and 20 minutes) of NP or of adipose tissue (AT) to the L4 DRG. AT was used as control for mechanical effects of NP application. RESULTS: Application of NP resulted in an increase of evoked thalamic responses to 138% +/- 10% of control after 20 minutes (P < 0.01), whereas AT application for 20 minutes resulted in a reduction of evoked responses to 77% +/- 4% (P < 0.05). Recordings in control animals (i.e., with no application) demonstrated stable evoked neuronal thalamic activity for up to 40 minutes. CONCLUSION: The study demonstrates that NP application onto DRG increases afferent fiber evoked responses in the thalamus and in view of the opposite effects of AT application suggests that these effects may be specific for NP. The results show that NP affects sensory transmitting pathways within a few minutes, possibly due to rapid and reversible alterations in the neuronal excitability. The study thus introduces a rodent model for studying sensory afferent evoked thalamic activity related to DRG injury which may be used to evaluate analgesics and anti-inflammatory drugs used for pain relief in disc herniation and neuropathic pain patients.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Fysiologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Physiology (hsv//eng)

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Kirurgi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Surgery (hsv//eng)

Nyckelord

Adipose Tissue

transplantation

Afferent Pathways

physiopathology

Animals

Back Pain

etiology

physiopathology

Disease Models

Animal

Electric Stimulation

Evoked Potentials

Female

Ganglia

Spinal

physiopathology

Injections

Epidural

Intervertebral Disk

transplantation

Intervertebral Disk Displacement

complications

physiopathology

Lumbar Vertebrae

Rats

Rats

Sprague-Dawley

Sciatic Nerve

physiopathology

Sensory Thresholds

Stress

Mechanical

Thalamus

physiopathology

Time Factors

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)