Lumbosacral spinal cord somatosensory evoked potentials for quantification of nociception in horses.

This research investigates the effectiveness of a technique known as lumbosacral spinal cord somatosensory evoked potentials (SSEP) in quantifying nociception, or the sensory nervous system’s response to harmful stimuli, in horses. The results suggest that this method could be used to measure how well different painkillers and painkilling methods work in these animals.

Research Methodology

• Researchers used lightly anaesthetised Shetland ponies for the study.
• SSEPs and electromyograms (EMG) from the horses’ epaxial muscles (near the spine) were recorded following electrical stimulation to the distal hindlimb (lower part of the back leg).
• The team examined the SSEP waveform and identified two distinct complexes, denoted as N1P1 and N2P2.
• The effect of epidurally applied methadone was also investigated as a part of this research.
• The researchers studied the effects of increasing stimulus intensity and calculated the conduction velocities (CV) of the stimulated nerves to ensure the validity of their model.

Key Findings

• The N2P2 complex in the SSEP waveform corresponded to nociceptive Adelta-afferent stimulation – the functioning of nerves that are sensitive to pain.
• The depressant effect of epidurally applied methadone showed it influenced the N2P2 complex, confirming its link to nociception.
• The N1P1 complex in the SSEP waveform arose from non-nociceptive Abeta-afferent stimulation – the functioning of nerves that do not typically respond to pain – and was not affected by epidurally applied methadone.

Conclusions and Implications

• The N2P2 complex in the SSEP has been identified as a valid measure of how the spinal cord processes nociception in horses.
• This research helps to validate the equine SSEP model, which can be used to study how effective new analgesics or painkilling methods are.
• These findings can enhance the protocols for caudal epidural analgesia in horses, an important method of managing pain during surgical and diagnostic procedures.