Differential suppression of the ipsi- and contralateral nociceptive reflexes in the neonatal rat spinal cord by agonists of µ-, δ- and κ-opioid receptors
Autor: | Boris V. Safronov, Liliana L. Luz, Elisabete C Fernandes, Olga Kononenko, Daniil Sarkisyan, Joana M. Duarte, Georgy Bakalkin |
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Rok vydání: | 2019 |
Předmět: |
0301 basic medicine
Agonist Male medicine.medical_specialty medicine.drug_class Receptors Opioid mu Pain (+)-Naloxone 03 medical and health sciences chemistry.chemical_compound 0302 clinical medicine Opioid receptor Internal medicine Receptors Opioid delta Reflex Medicine Animals Rats Wistar Neurotransmitter Molecular Biology Endogenous opioid Morphine business.industry Naloxone General Neuroscience Receptors Opioid kappa Nociceptors Spinal cord Rats Analgesics Opioid DAMGO 030104 developmental biology Endocrinology medicine.anatomical_structure Opioid chemistry Animals Newborn Spinal Cord Receptors Opioid Female Neurology (clinical) business 030217 neurology & neurosurgery Developmental Biology medicine.drug |
Zdroj: | Brain Research |
ISSN: | 0006-8993 |
DOI: | 10.1016/j.brainres.2019.04.026 |
Popis: | Nociceptive discharges caused by the unilateral tissue damage are processed in the spinal cord by both ipsi- and contralateral neuronal circuits. The mechanisms of the neurotransmitter control of this bilateral excitation spread is poorly understood. Spinally administered opiates are known to suppress nociceptive transmission and nociceptive withdrawal reflexes. Here we investigated whether three major types of opioid receptors are involved in the bilateral control of the spinal nociceptive sensorimotor processing. Effects of the µ-, δ- and κ-opioid receptor agonists on the ipsi- and contralateral nociceptive reflexes were studied by recording slow ventral root potentials in an isolated spinal cord preparation of the new-born rat. Absolute levels of expression of the opioid genes were analyzed by the droplet digital PCR. Ipsi- and contralateral slow ventral root potentials were most strongly suppressed by the µ-opioid receptor agonist DAMGO, by 63% and 85%, followed by the κ-opioid receptor agonist U-50488H, by 44% and 73%, and δ-opioid receptor agonist leucine-enkephalin, by 27% and 49%, respectively. All these agonists suppressed stronger contra- than ipsilateral responses. Naloxone prevented effects of the agonists indicating that they act through opioid receptors, which, as we show, are expressed in the neonatal spinal cord at the levels similar to those in adults. Thus, opioid receptor agonists suppress the segmental nociceptive reflexes. Stronger contralateral effects suggest that the endogenous opioid system regulates sensorimotor processing in the spinal commissural pathways. These effects of opioids may be relevant for treatment of symmetric clinical pain symptoms caused by unilateral tissue injury. |
Databáze: | OpenAIRE |
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