Neuronal Model of Tactile Allodynia Produced by Spinal Strychnine: Effects of Excitatory Amino Acid Receptor Antagonists and a Mu-Opiate Receptor Agonist

The study investigated the effects of spinal strychnine on tactile allodynia in cats, focusing on the role of excitatory amino acid receptor antagonists and a μ-opiate receptor agonist. Strychnine enhanced responses to hair deflection and expanded low threshold receptive fields in dorsal horn neurons. NMDA receptor antagonist AP-7 blocked these effects without altering original receptive fields, while non-NMDA antagonist CNQX blocked both low and high intensity inputs. The μ-opiate receptor agonist alfentanil reduced responsiveness to high intensity stimulation but did not affect hair deflection responses. The findings suggested that loss of glycinergic input may contribute to pain states similar to post-nerve injury in humans, and that targeting these pathways could improve treatments for pain conditions resistant to opioids.