Because of current, limited options for treating painful disorders in the lower urinary tract (LUT) such as interstitial cystitis (1C) or chronic pelvic pain syndrome (CPPS), there is a great demand for the development of new treatment strategy. Supported by NIH grant """"""""Afferent plasticity underlying urethral and pelvic pain"""""""" R01 DK57267, 09/01/1999- 08/31/2003, we found that; (1) there is a considerable heterogeneity in afferent fiber populations in visceral neural pathways to the bladder/proximal urethra and somatic neural pathways to the external urethral sphincter (EUS)/pelvic floor, and (2) tissue inflammation of bladder/urethra and nerve injury of somatic pudendal nerves can induce bladder/urethral hyperactivity associated with C-fiber afferent hyperexcitability due to a reduction in different types of voltage-gated K+ currents. Thus, the goals of this proposed project are to further identify the mechanismsinducing afferent hyperexcitability related to LUT pain, especially focusing on the role and neurotrophic factor-dependent regulation of C-fiber afferents (i.e., peptidergic and non-peptidergic populations). We will first examine the effects of the ribosome-inactivating toxin saporin conjugated with isolectin B4, which can theoretically suppress afferent transmission via IB4-binding, non-peptidergic C-fiber afferent pathways. This will allow us to identify the functional role of non-peptidergic C-fiber afferents in pain conditions arising from different regions of the LUT. Secondly, we will explore the regulatory role of two different neurotrophic factors (NGF and GDNF) in the emergence of C-fiber hyperexcitability involved in LUT pain since these two factors reportedly modulate the functional properties of peptidergic and non-peptidergic C-fiber afferent pathways, respectively. Thirdly, we will seek to elucidate molecular identities of voltage-gated K+ (Kv) channels responsible for C-fiber hyperexcitability since altered expression of Kv channels was shown to contribute to C-fiber hyperexcitability in LUT pain conditions in our previous study.
The Specific Aims of this proposal using animals models of urethral or pelvic pain are: I) to investigate the effects of targeting non-peptidergic C-fiber afferent pathways on LUT pain conditions using saporin conjugates; II) to investigate the effects of NGF/GDNF and their antibodies on LUT pain conditions; and III) to identify the changes in expression of Kv channel subunits in LUT afferent neurons and the correlation with a reduction of K+ current subtypes and C-fiber afferent neuron hyperexcitability. The long-term objectives of the research program are to identify the detailed mechanisms and new, effective therapeutic targets for pain conditions in the LUT. This is recognized as a high priority in the urologic care of patients with IC/CPPS.
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