Pain caused by nerve injury accompanies a wide variety of conditions such as trauma, surgical incision and amputation, inflammation, HIV/AIDS and cancer, and is inadequately treated by currently available methods. Primary sensory neurons, including their somata in the dorsal root ganglia (DRG), are critical sites of pathology, yet their potential as a therapeutic target has not been pursued. We have previously shown peripheral nerve injury causes loss of inward Ca2+ flux (ICa) that elevates sensory neuron firing and contributes to neuropathic pain behavior in rats. The currently proposed research will extend these findings. Specifically, our FIRST AIM is to examine the novel theory that nerve injury causes hyperalgesia by depressing the activity of CaMKII, a molecular decoder of neuronal frequency information. Ca2+ channels admit a diminished inward flux of Ca2+ as pCaMKII diminishes. We have established a strong link between low ICa and increased excitability. Thus, neuronal activation after injury results in a greater burst of afferent impulses and an amplified pain experience. Accordingly, we will test this overall hypothesis by quantifying CaMKII protein and function after injury. Further, we will use pharmacologic and genetic strategies to block and activate CaMKII to examine its role in regulating neuronal electrophysiology.
Our SECOND AIM i s to determine the effect of CaMKII on the intracellular Ca2+ signal. Despite the central role of Ca2+ in controlling neuronal function, there has been minimal investigation of the influence of nerve injury and associated changes in CaMKII on the critical processes that shape the Ca2+ signal. Accordingly, we will examine Ca2+ management in injured and control rats while altering CaMKII activity pharmacologically and by CaMKII knockdown through siRNA expression. Specific Ca2+ uptake and release pathways will be examined while measuring Ca2+ in subcellular compartments. In our THIRD AIM, the importance of CaMKII regulation of Ca2+ in pain will be directly tested by measuring pain behavior in rats during selective genetic and pharmacologic modulation of CaMKII activity within specific DRGs. Importance to Public Health: This project will provide better understanding of how nerve injury causes chronic pain. This new knowledge may lead to the development of therapies that are delivered selectively to the peripheral nerve, in order to correct abnormal Ca2+ signaling and thereby relieve nerve injury pain.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Surgery, Anesthesiology and Trauma Study Section (SAT)
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Porter, Linda L
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Medical College of Wisconsin
Schools of Medicine
United States
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Yu, Hongwei; Pan, Bin; Weyer, Andy et al. (2015) CaMKII Controls Whether Touch Is Painful. J Neurosci 35:14086-102
Bangaru, M L Y; Meng, J; Kaiser, D J et al. (2015) Differential expression of CaMKII isoforms and overall kinase activity in rat dorsal root ganglia after injury. Neuroscience 300:116-27
Pan, Bin; Guo, Yuan; Kwok, Wai-Meng et al. (2014) Sigma-1 receptor antagonism restores injury-induced decrease of voltage-gated Ca2+ current in sensory neurons. J Pharmacol Exp Ther 350:290-300
Hogan, Quinn H; Sprick, Chelsea; Guo, Yuan et al. (2014) Divergent effects of painful nerve injury on mitochondrial Ca(2+) buffering in axotomized and adjacent sensory neurons. Brain Res 1589:112-25
Kostic, Sandra; Pan, Bin; Guo, Yuan et al. (2014) Regulation of voltage-gated Ca(2+) currents by Ca(2+)/calmodulin-dependent protein kinase II in resting sensory neurons. Mol Cell Neurosci 62:10-8
Bangaru, Madhavi L; Weihrauch, Dorothee; Tang, Qing-Bo et al. (2013) Sigma-1 receptor expression in sensory neurons and the effect of painful peripheral nerve injury. Mol Pain 9:47
Gemes, Geza; Koopmeiners, Andrew; Rigaud, Marcel et al. (2013) Failure of action potential propagation in sensory neurons: mechanisms and loss of afferent filtering in C-type units after painful nerve injury. J Physiol 591:1111-31
Duncan, C; Mueller, S; Simon, E et al. (2013) Painful nerve injury decreases sarco-endoplasmic reticulum Caýýýýý-ATPase activity in axotomized sensory neurons. Neuroscience 231:247-57
Tang, Qingbo; Bangaru, Madhavi Latha Yadav; Kostic, Sandra et al. (2012) Caýýýýý-dependent regulation of Caýýýýý currents in rat primary afferent neurons: role of CaMKII and the effect of injury. J Neurosci 32:11737-49
Gemes, Geza; Oyster, Katherine D; Pan, Bin et al. (2012) Painful nerve injury increases plasma membrane Ca2+-ATPase activity in axotomized sensory neurons. Mol Pain 8:46

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