Sustained morphine treatment augments capsaicin-evoked calcitonin gene-related peptide release from primary sensory neurons in a protein kinase A- and Raf-1-dependent manner

Suneeta Tumati, Henry I. Yamamura, Todd W. Vanderah, William R. Roeske, Eva V. Varga

Research output: Contribution to journalArticle

20 Scopus citations


Studies have shown that long-term (5α,6α)-7,8-didehydro-4,5- epoxy-17-methylmorphinan-3,6-diol (morphine) treatment increases the sensitivity to painful heat stimuli (thermal hyperalgesia). The cellular adaptations contributing to sustained morphine-mediated pain sensitization are not fully understood. It was shown previously (J Neurosci 22:6747-6755, 2002) that sustained morphine exposure augments pain neurotransmitter [such as calcitonin gene-related peptide (CGRP)] release in the dorsal horn of the spinal cord in response to the heat-sensing transient receptor potential vanilloid 1 receptor agonist 8-methyl-N-vanillyl-6-nonenamide (capsaicin). In the present study, we demonstrate that sustained morphine-mediated augmentation of CGRP release from isolated primary sensory dorsal root ganglion neurons is dependent on protein kinase A and Raf-1 kinase. Our data indicate that, in addition to neural system adaptations, sustained opioid agonist treatment also produces intracellular compensatory adaptations in primary sensory neurons, leading to augmentation of evoked pain neurotransmitter release from these cells.

Original languageEnglish (US)
Pages (from-to)810-817
Number of pages8
JournalJournal of Pharmacology and Experimental Therapeutics
Issue number3
StatePublished - Sep 21 2009


ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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