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- Zhang, Q., et al.
(författare)
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Na+ current properties in islet alpha- and beta-cells reflect cell-specific Scn3a and Scn9a expression
- 2014
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Ingår i: Journal of Physiology-London. - : Wiley. - 0022-3751 .- 1469-7793. ; 592:21, s. 4677-4696
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Tidskriftsartikel (refereegranskat)abstract
- - and -cells express both Na(v)1.3 and Na(v)1.7 Na+ channels but in different relative amounts. The differential expression explains the different properties of Na+ currents in - and -cells. Na(v)1.3 is the functionally important Na+ channel subunit in both - and -cells. Islet Na(v)1.7 channels are locked in an inactive state due to an islet cell-specific factor. Mouse pancreatic - and -cells are equipped with voltage-gated Na+ currents that inactivate over widely different membrane potentials (half-maximal inactivation (V-0.5) at -100mV and -50mV in - and -cells, respectively). Single-cell PCR analyses show that both - and -cells have Na(v)1.3 (Scn3) and Na(v)1.7 (Scn9a) subunits, but their relative proportions differ: -cells principally express Na(v)1.7 and -cells Na(v)1.3. In -cells, genetically ablating Scn3a reduces the Na+ current by 80%. In -cells, knockout of Scn9a lowers the Na+ current by >85%, unveiling a small Scn3a-dependent component. Glucagon and insulin secretion are inhibited in Scn3a(-/-) islets but unaffected in Scn9a-deficient islets. Thus, Na(v)1.3 is the functionally important Na+ channel subunit in both - and -cells because Na(v)1.7 is largely inactive at physiological membrane potentials due to its unusually negative voltage dependence of inactivation. Interestingly, the Na(v)1.7 sequence in brain and islets is identical and yet the V-0.5 for inactivation is >30mV more negative in -cells. This may indicate the presence of an intracellular factor that modulates the voltage dependence of inactivation.
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| 2. |
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| 3. |
- Zhao, Jing, et al.
(författare)
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Nociceptor-expressed ephrin-B2 regulates inflammatory and neuropathic pain
- 2010
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Ingår i: Molecular Pain. - : SAGE Publications. - 1744-8069. ; 6, s. 77-
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Tidskriftsartikel (refereegranskat)abstract
- Background:EphB receptors and their ephrin-B ligands play an important role in nervous system development, as well as synapse formation and plasticity in the adult brain. Recent studies show that intrathecal treatment with EphB-receptor activator ephrinB2-Fc induced thermal hyperalgesia and mechanical allodynia in rat, indicating that ephrin-B2 in small dorsal root ganglia (DRG) neurons and EphB receptors in the spinal cord modulate pain processing. To examine the role of ephrin-B2 in peripheral pain pathways, we deleted ephrin-B2 in Nav1.8+ nociceptive sensory neurons with the Cre-loxP system. Sensory neuron numbers and terminals were examined using neuronal makers. Pain behavior in acute, inflammatory and neuropathic pain models was assessed in the ephrin-B2 conditional knockout (CKO) mice. We also investigated the c-Fos expression and NMDA receptor NR2B phosphorylation in ephrin-B2 CKO mice and littermate controls.Results:The ephrin-B2 CKO mice were healthy with no sensory neuron loss. However, pain-related behavior was substantially altered. Although acute pain behavior and motor co-ordination were normal, inflammatory pain was attenuated in ephrin-B2 mutant mice. Complete Freund's adjuvant (CFA)-induced mechanical hyperalgesia was halved. Formalin-induced pain behavior was attenuated in the second phase, and this correlated with diminished tyrosine phosphorylation of N-methyl-D-aspartic acid (NMDA) receptor subunit NR2B in the dorsal horn. Thermal hyperalgesia and mechanical allodynia were significantly reduced in the Seltzer model of neuropathic pain.Conclusions:Presynaptic ephrin-B2 expression thus plays an important role in regulating inflammatory pain through the regulation of synaptic plasticity in the dorsal horn and is also involved in the pathogenesis of some types of neuropathic pain.
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