Opioids suppress spontaneous activity of polymodal nociceptors in rat paw skin induced by ultraviolet irradiation

doi:10.1016/0306-4522(94)90456-1

Neuroscience

Volume 58, Issue 4, February 1994, Pages 793-798

https://doi.org/10.1016/0306-4522(94)90456-1 Get rights and content

Abstract

Changes in chemical sensitivity of periperal nociceptors following injury or inflammation have been studied in in vitro preparation of the saphenous nerve-hind paw skin from adult rats. Heat hyperalgesia in the hind paw was induced by a prior ultraviolet irradiation and the skin from these animals was investigated five days later. Polymodal nociceptors were quiescent in normal skin but were spontaneously active in the majority of fibres after ultraviolet exposure. Capsaicin-induced activation of fine fibres was enhanced after ultraviolet pretreatment. Direct administration of morphine, DAGOL (μ-receptor agonist) and U-69593 (k-receptor agonist), but not DPDPE (δ-receptor agonist) to the receptive field produced a concentration-related and naloxone-reversible suppression of spontaneous firing in polymodal nociceptors of ultraviolet-treated skin. Morphine did not reduce the activity of fibres in normal skin when these were driven by KCl depolarization.

These data show that polymodal nociceptors change their activity and sensitivity to exogenous chemicals following the induction of peripheral hyperalgesia by ultraviolet irradiation. Specifically, evidence is provided for the expression of opioid sensitivity and inhibition of polymodal nociceptor activity through μ- and k-opioid receptors. These observations may account for peripheral antinociceptive actions of opioids during specific states of peripheral hyperalgesia.

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Opioids suppress spontaneous activity of polymodal nociceptors in rat paw skin induced by ultraviolet irradiation

Abstract

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Trends pharmac. Sci.

Biochem. Pharmac.

Prostaglandins

J. auton. nerv. Syst.

J. invest. Dermat.

Neuroscience

Pain

Brain Res.

Neurosci. Lett.

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Eur. J. Pharmac.

Eur J. Pharmac.

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Pain

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Neuropharmacology

J. Pain Symptom Manag.

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Neuron

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Inhibition of nociceptor activity by receptor selective opioids studied in an isolated skin/nerve preparation from hyperalgesic rats

J. Physiol.