Abstract
In this study, we examined the expression of insulin-like growth factor I (IGF-I) and its receptor (IGF-IR) in dorsal root ganglia (DRG) neurons in two rodent models of nerve injury: sciatic nerve axotomy and streptozotocin-induced (STZ) painful diabetic neuropathy. We demonstrate that IGF-I and its receptor are preferentially expressed in small (< 25 microm diameter) DRG neurons. There is a significant down-regulation in the expression of IGF-I and IGF-IR in the small DRG neurons of STZ rats by 59% and 71%, respectively. A parallel reduction in expression is shown in axotomized < 25 microm diameter DRG neurons for IGF-I (47%) but not for IGF-IR. The loss of IGF-I support to a population of predominantly nociceptive neurons may contribute to neuropathic pain observed in these models.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Afferent Pathways / metabolism*
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Afferent Pathways / physiopathology
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Animals
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Axotomy
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Cell Size / physiology
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Diabetes Mellitus, Experimental / complications
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Diabetes Mellitus, Experimental / physiopathology
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Diabetic Neuropathies / metabolism
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Diabetic Neuropathies / physiopathology
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Disease Models, Animal
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Down-Regulation / physiology*
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Ganglia, Spinal / metabolism*
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Ganglia, Spinal / physiopathology
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Immunohistochemistry
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Insulin-Like Growth Factor I / metabolism*
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Male
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Nerve Degeneration / metabolism
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Nerve Degeneration / physiopathology
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Nerve Fibers, Unmyelinated / metabolism*
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Neuralgia / metabolism*
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Neuralgia / physiopathology
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Nociceptors / metabolism*
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Peripheral Nervous System Diseases / metabolism*
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Peripheral Nervous System Diseases / physiopathology
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Rats
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Rats, Sprague-Dawley
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Receptor, IGF Type 1 / metabolism
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Sciatic Nerve / injuries
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Sciatic Nerve / metabolism
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Sciatic Nerve / surgery
Substances
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Insulin-Like Growth Factor I
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Receptor, IGF Type 1