Wise Young
10-02-2001, 12:36 AM
Journal of Neurochemistry, Vol. 77, No. 3, 2001 864-875
© 2001 International Society for Neurochemistry
Nerve growth factor induces P2X3 expression in sensory neurons
Matt S. Ramer, Elizabeth J. Bradbury and Stephen B. McMahon
Sensory Function Group, Centre for Neuroscience Research, Guy's King's and St. Thomas' School of Biomedical Science, King's College London, London, UK
Address correspondence and reprints requests to Matt S. Ramer, Sensory Function Group, Centre for Neuroscience Research, Guy's, King's and St Thomas' School of Biomedical Science, King's College London, Hodgkin Building, Guy's Campus, London Bridge, London SE1 1UL, UK. E-mail: matt.ramer@kcl.ac.uk
Glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) are neuroprotective for subpopulations of sensory neurons and thus are candidates for pain treatment. However, delivering these factors to damaged neurons will invariably result in undamaged systems also being treated, with possible consequences for sensory processing. In sensory neurons the purinergic receptor P2X3 is found predominantly in GDNF-sensitive nociceptors. ATP signalling via the P2X3 receptor may contribute to pathological pain, suggesting an important role for this receptor in regulating nociceptive function. We therefore investigated the effects of intrathecal GDNF or NGF on P2X3 expression in adult rat spinal cord and dorsal root ganglia (DRG). In control spinal cords, P2X3 expression was restricted to a narrow band of primary afferent terminals within inner lamina II (IIi). Glial cell line-derived neurotrophic factor treatment increased P2X3 immunoreactivity within lamina IIi but not elsewhere in the cord. Nerve growth factor treatment, however, induced novel P2X3 expression, with intense immunoreactivity in axons projecting to lamina I and outer lamina II and to the ventro-medial afferent bundle beneath the central canal. In the normal DRG, we found a greater proportion of P2X3-positive neurons at cervical levels, many of which were large-diameter and calcitonin gene-related peptide-positive. In both cervical and lumbar DRG, the number of P2X3-positive cells increased following GDNF or NGF treatment. De novo expression of P2X3 in NGF-sensitive nociceptors may contribute to chronic inflammatory pain.
Key Words: ATP - immunohistochemistry - ion channels - neurotrophic factors - nociceptors - pain - spinal cord
Abbreviations used: CCI, chronic constriction injury; CGRP, calcitonin gene-related peptide; CTB, B fragment of cholera toxin; DRG, dorsal root ganglion; FITC, fluorescein isothiocyanate; FRAP, fluoride-resistant acid phosphatase; GDNF, glial cell-derived neurotrophic factor; IB4, isolectin 4; NGF, nerve growth factor; PB, phosphate buffer; PBS, phosphate-buffered saline; PF, paraformaldeyde; SP, substance P; TSA, tyramide signal amplification; VMAB, ventro-medial afferent bundle.
© 2001 International Society for Neurochemistry
Nerve growth factor induces P2X3 expression in sensory neurons
Matt S. Ramer, Elizabeth J. Bradbury and Stephen B. McMahon
Sensory Function Group, Centre for Neuroscience Research, Guy's King's and St. Thomas' School of Biomedical Science, King's College London, London, UK
Address correspondence and reprints requests to Matt S. Ramer, Sensory Function Group, Centre for Neuroscience Research, Guy's, King's and St Thomas' School of Biomedical Science, King's College London, Hodgkin Building, Guy's Campus, London Bridge, London SE1 1UL, UK. E-mail: matt.ramer@kcl.ac.uk
Glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF) are neuroprotective for subpopulations of sensory neurons and thus are candidates for pain treatment. However, delivering these factors to damaged neurons will invariably result in undamaged systems also being treated, with possible consequences for sensory processing. In sensory neurons the purinergic receptor P2X3 is found predominantly in GDNF-sensitive nociceptors. ATP signalling via the P2X3 receptor may contribute to pathological pain, suggesting an important role for this receptor in regulating nociceptive function. We therefore investigated the effects of intrathecal GDNF or NGF on P2X3 expression in adult rat spinal cord and dorsal root ganglia (DRG). In control spinal cords, P2X3 expression was restricted to a narrow band of primary afferent terminals within inner lamina II (IIi). Glial cell line-derived neurotrophic factor treatment increased P2X3 immunoreactivity within lamina IIi but not elsewhere in the cord. Nerve growth factor treatment, however, induced novel P2X3 expression, with intense immunoreactivity in axons projecting to lamina I and outer lamina II and to the ventro-medial afferent bundle beneath the central canal. In the normal DRG, we found a greater proportion of P2X3-positive neurons at cervical levels, many of which were large-diameter and calcitonin gene-related peptide-positive. In both cervical and lumbar DRG, the number of P2X3-positive cells increased following GDNF or NGF treatment. De novo expression of P2X3 in NGF-sensitive nociceptors may contribute to chronic inflammatory pain.
Key Words: ATP - immunohistochemistry - ion channels - neurotrophic factors - nociceptors - pain - spinal cord
Abbreviations used: CCI, chronic constriction injury; CGRP, calcitonin gene-related peptide; CTB, B fragment of cholera toxin; DRG, dorsal root ganglion; FITC, fluorescein isothiocyanate; FRAP, fluoride-resistant acid phosphatase; GDNF, glial cell-derived neurotrophic factor; IB4, isolectin 4; NGF, nerve growth factor; PB, phosphate buffer; PBS, phosphate-buffered saline; PF, paraformaldeyde; SP, substance P; TSA, tyramide signal amplification; VMAB, ventro-medial afferent bundle.