TY - JOUR T1 - 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 JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 810 LP - 817 DO - 10.1124/jpet.109.151704 VL - 330 IS - 3 AU - Suneeta Tumati AU - Henry I. Yamamura AU - Todd W. Vanderah AU - William R. Roeske AU - Eva V. Varga Y1 - 2009/09/01 UR - http://jpet.aspetjournals.org/content/330/3/810.abstract N2 - 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. The American Society for Pharmacology and Experimental Therapeutics ER -