TY - JOUR
T1 - Molecular and functional expression of cation-chloride cotransporters in dorsal root ganglion neurons during postnatal maturation
AU - Mao, Shihong
AU - Garzon-Muvdi, Tomás
AU - Di Fulvio, Mauricio
AU - Chen, Yanfang
AU - Delpire, Eric
AU - Alvarez, Francisco J.
AU - Alvarez-Leefmans, Francisco J.
PY - 2012/8/1
Y1 - 2012/8/1
N2 - GABA depolarizes and excites central neurons during early development, becoming inhibitory and hyperpolarizing with maturation. This "developmental shift" occurs abruptly, reflecting a decrease in intracellular Cl- concentration ([Cl-]i) and a hyperpolarizing shift in Cl- equilibrium potential due to upregulation of the K+-Cl- cotransporter KCC2b, a neuron-specific Cl- extruder. In contrast, primary afferent neurons (PANs) are depolarized by GABA throughout adulthood because of expression of NKCC1, a Na+-K+-2Cl- cotransporter that accumulates Cl- above equilibrium. The GABA A -mediated depolarization of PANs determines presynaptic inhibition in the spinal cord, a key mechanism gating somatosensory information. Little is known about developmental changes in Cl- transporter expression and Cl- homeostasis in PANs. Whether NKCC1 is expressed in PANs of all phenotypes or is restricted to subpopulations (e.g., nociceptors) is debatable. Likewise, whether PANs express KCC2s is controversial. We investigated NKCC1 and K+-Cl- cotransporter expression in rat and mouse dorsal root ganglion (DRG) neurons with molecular methods. Using fluorescence imaging microscopy, we measured [Cl-]i in acutely dissociated rat DRG neurons (P0-P21) loaded with N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide and Classified with phenotypic markers. DRG neurons of all sizes express two NKCC1 mRNAs, one full-length and a shorter splice variant lacking exon 21. Immunolabeling with validated antibodies revealed ubiquitous expression of NKCC1 in DRG neurons irrespective of postnatal age and phenotype. As maturation progresses [Cl-]i decreases gradually, persisting above equilibrium in >95% mature neurons. DRG neurons express mRNAs for KCC1, KCC3s, and KCC4, but not for KCC2s. Mechanisms underlying PANs' developmental changes in Cl- homeostasis are discussed and compared with those of central neurons.
AB - GABA depolarizes and excites central neurons during early development, becoming inhibitory and hyperpolarizing with maturation. This "developmental shift" occurs abruptly, reflecting a decrease in intracellular Cl- concentration ([Cl-]i) and a hyperpolarizing shift in Cl- equilibrium potential due to upregulation of the K+-Cl- cotransporter KCC2b, a neuron-specific Cl- extruder. In contrast, primary afferent neurons (PANs) are depolarized by GABA throughout adulthood because of expression of NKCC1, a Na+-K+-2Cl- cotransporter that accumulates Cl- above equilibrium. The GABA A -mediated depolarization of PANs determines presynaptic inhibition in the spinal cord, a key mechanism gating somatosensory information. Little is known about developmental changes in Cl- transporter expression and Cl- homeostasis in PANs. Whether NKCC1 is expressed in PANs of all phenotypes or is restricted to subpopulations (e.g., nociceptors) is debatable. Likewise, whether PANs express KCC2s is controversial. We investigated NKCC1 and K+-Cl- cotransporter expression in rat and mouse dorsal root ganglion (DRG) neurons with molecular methods. Using fluorescence imaging microscopy, we measured [Cl-]i in acutely dissociated rat DRG neurons (P0-P21) loaded with N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide and Classified with phenotypic markers. DRG neurons of all sizes express two NKCC1 mRNAs, one full-length and a shorter splice variant lacking exon 21. Immunolabeling with validated antibodies revealed ubiquitous expression of NKCC1 in DRG neurons irrespective of postnatal age and phenotype. As maturation progresses [Cl-]i decreases gradually, persisting above equilibrium in >95% mature neurons. DRG neurons express mRNAs for KCC1, KCC3s, and KCC4, but not for KCC2s. Mechanisms underlying PANs' developmental changes in Cl- homeostasis are discussed and compared with those of central neurons.
KW - Intracellular chloride regulation
KW - KCC1
KW - KCC2
KW - KCC3
KW - KCC4
KW - NKCC1
KW - Primary sensory neurons
UR - http://www.scopus.com/inward/record.url?scp=84863487789&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84863487789&partnerID=8YFLogxK
U2 - 10.1152/jn.00970.2011
DO - 10.1152/jn.00970.2011
M3 - Article
C2 - 22457464
AN - SCOPUS:84863487789
SN - 0022-3077
VL - 108
SP - 834
EP - 852
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 3
ER -