The processing of nociceptive information in the spinal dorsal horn may change significantlyfollowing peripheral nerve injury or inflammation to ultimately lead to the development of persistent pain. We previously established that loose ligation of the sciatic nerve was closely associated with (1) activity- dependent long-lasting synaptic plasticity and (2) the activation of cyclic AMP response element binding protein (CREB). CREB activation alters the expression of many genes, including those coding for the post- synaptic density (PSD) proteins Homer and Shank. The Homerla, Ib and Ic and Shankl and 2 isoforms may play important roles in the activity-dependent remodeling of the PSD that ultimately leads to increased synaptic efficacy. In the present application we will investigate the relationship between loose ligation of the sciatic nerve and these Homer and Shank isoforms. Our central hypothesis is that sciatic ligation-associated regulation of Homerla, Ib and Ic and Shankl &2 gene expression promotes the remodeling of the post- synaptic density (PSD) in spinal dorsal horn neurons. We surmise that this remodeling critically contributes to the long-lasting increases in synaptic efficacy that eventually lead to neuropathic pain, hi Specific Aim 1 we will examine if selected pre-transcriptional mediators 'translate'the sciatic ligation into changes in Homer and Shank gene expression, hi Specific Aim 2 we will employ specific small interfering RNAs in an attempt to 'silence'Homer and Shank gene expression and establish whether this modifies their protein levels and distribution in the PSD of spinal dorsal horn neurons within hours of the sciatic ligation.
In Specific Aim 3 we seek to establish if manipulations of Homer and Shank gene expression and protein levels alter mechanical allodynia and thermal hyperalgesia as behavioral signs of neuropathic pain several days after the sciatic ligation. We strive to achieve two main goals in this proposal. First, from a cellular perspective we wish to delineate the consequences of injury-elicited primary afferent activity on the PSD structure in the spinal dorsal horn. Second, from a therapeutic perspective, we seek to achieve better target specificity. The remodeled PSD may be a common reflection of injury-elicited changes in several receptors, pathways, transcription factors and genes. If our experiments suggest that regulation of Homer and Shank gene expression plays an important role in the remodeling of the 'pain'PSD then our successful completion of this proposal should provide a solid basis for future therapeutic interventions.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Somatosensory and Chemosensory Systems Study Section (SCS)
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Porter, Linda L
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University of Wisconsin Madison
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Miletic, Gordana; Lippitt, Jennifer A; Sullivan, Kristine M et al. (2013) Loss of calcineurin in the spinal dorsal horn contributes to neuropathic pain, and intrathecal administration of the phosphatase provides prolonged analgesia. Pain 154:2024-33
Miletic, G; Sullivan, K M; Dodson, A M K et al. (2011) Changes in calcineurin message, enzyme activity and protein content in the spinal dorsal horn are associated with chronic constriction injury of the rat sciatic nerve. Neuroscience 188:142-7
Miletic, Gordana; Dumitrascu, Catalina I; Honstad, Christopher E et al. (2010) Loose ligation of the rat sciatic nerve elicits early accumulation of Shank1 protein in the post-synaptic density of spinal dorsal horn neurons. Pain 149:152-9
Miletic, Gordana; Driver, Ashley M; Miyabe-Nishiwaki, Takako et al. (2009) Early changes in Homer1 proteins in the spinal dorsal horn are associated with loose ligation of the rat sciatic nerve. Anesth Analg 109:2000-7
Miletic, Gordana; Miletic, Vjekoslav (2008) Loose ligation of the sciatic nerve is associated with TrkB receptor-dependent decreases in KCC2 protein levels in the ipsilateral spinal dorsal horn. Pain 137:532-9
Sample, Susannah J; Behan, Mary; Smith, Lesley et al. (2008) Functional adaptation to loading of a single bone is neuronally regulated and involves multiple bones. J Bone Miner Res 23:1372-81
Shih, Andre; Miletic, Vjekoslav; Miletic, Gordana et al. (2008) Midazolam administration reverses thermal hyperalgesia and prevents gamma-aminobutyric acid transporter loss in a rodent model of neuropathic pain. Anesth Analg 106:1296-302, table of contents
Miletic, Gordana; Pankratz, Matthew T; Miletic, Vjekoslav (2002) Increases in the phosphorylation of cyclic AMP response element binding protein (CREB) and decreases in the content of calcineurin accompany thermal hyperalgesia following chronic constriction injury in rats. Pain 99:493-500
Miletic, G; Miletic, V (2000) Long-term changes in sciatic-evoked A-fiber dorsal horn field potentials accompany loose ligation of the sciatic nerve in rats. Pain 84:353-9