Itch and analgesia resulting from intrathecal application of morphine: Contrasting effects on different populations of trigeminothalamic tract neurons

Hannah R. Moser, Glenn J. Giesler

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24 Scopus citations

Abstract

Intrathecal application of morphine is among the most powerful methods used to treat severe chronic pain. However, this approach commonly produces itch sufficiently severe that patients are forced to choose between relief of pain or itch. The neuronal populations responsible for processing and transmitting information underlying itch caused by intrathecal application of morphine have not been identified and characterized. We describe two populations of antidromically identified trigeminothalamic tract (VTT) neurons in anesthetized rats that are differentially affected by morphine and explain several aspects of opioid-induced itch and analgesia. We found that intrathecal application of morphine increased ongoing activity of itch-responsive VTT neurons. In addition, intrathecal application of morphine increased responses to pruritogens injected into the skin and greatly heightened responses to innocuous mechanical stimuli. In contrast, the ongoing activity and responses to noxious pinches in nociceptiveVTTneurons were frequently inhibited by the same dose of morphine. These results reveal that i.t. application of morphine affects specific subpopulations of VTT neurons in ways that may produce itch, hyperknesis, alloknesis, and analgesia.

Original languageEnglish (US)
Pages (from-to)6093-6101
Number of pages9
JournalJournal of Neuroscience
Volume33
Issue number14
DOIs
StatePublished - Apr 3 2013

Bibliographical note

Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.

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