Hypocretin/orexin and nociceptin/orphanin FQ coordinately regulate analgesia in a mouse model of stress-induced analgesia
Xinmin Xie, … , Lawrence Toll, Thomas S. Kilduff
Xinmin Xie, … , Lawrence Toll, Thomas S. Kilduff
Published June 12, 2008
Citation Information: J Clin Invest. 2008;118(7):2471-2481. https://doi.org/10.1172/JCI35115.
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Research Article Neuroscience

Hypocretin/orexin and nociceptin/orphanin FQ coordinately regulate analgesia in a mouse model of stress-induced analgesia

Abstract

Stress-induced analgesia (SIA) is a key component of the defensive behavioral “fight-or-flight” response. Although the neural substrates of SIA are incompletely understood, previous studies have implicated the hypocretin/orexin (Hcrt) and nociceptin/orphanin FQ (N/OFQ) peptidergic systems in the regulation of SIA. Using immunohistochemistry in brain tissue from wild-type mice, we identified N/OFQ-containing fibers forming synaptic contacts with Hcrt neurons at both the light and electron microscopic levels. Patch clamp recordings in GFP-tagged mouse Hcrt neurons revealed that N/OFQ hyperpolarized, decreased input resistance, and blocked the firing of action potentials in Hcrt neurons. N/OFQ postsynaptic effects were consistent with opening of a G protein–regulated inwardly rectifying K+ (GIRK) channel. N/OFQ also modulated presynaptic release of GABA and glutamate onto Hcrt neurons in mouse hypothalamic slices. Orexin/ataxin-3 mice, in which the Hcrt neurons degenerate, did not exhibit SIA, although analgesia was induced by i.c.v. administration of Hcrt-1. N/OFQ blocked SIA in wild-type mice, while coadministration of Hcrt-1 overcame N/OFQ inhibition of SIA. These results establish what is, to our knowledge, a novel interaction between the N/OFQ and Hcrt systems in which the corticotropin-releasing factor and N/OFQ systems coordinately modulate the Hcrt neurons to regulate SIA.

Authors

Xinmin Xie, Jonathan P. Wisor, Junko Hara, Tara L. Crowder, Robin LeWinter, Taline V. Khroyan, Akihiro Yamanaka, Sabrina Diano, Tamas L. Horvath, Takeshi Sakurai, Lawrence Toll, Thomas S. Kilduff

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Figure 3

N/OFQ modulates membrane currents and depresses intracellular Ca2+ levels.

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N/OFQ modulates membrane currents and depresses intracellular Ca2+ level...
(A–C) N/OFQ activates a K+ conductance. The I-V relationship of neuronal responses in the presence (B) and absence (A) of N/OFQ (1 μM) indicates a reversal potential of –98 mV (C), which is close to the K+ equilibrium potential (approximately –110 mV) under our experimental conditions. Before N/OFQ application, membrane potential was adjusted to a resting level of –60 mV by DC current injection. (D) N/OFQ inhibits Ca2+ currents. From a Vh of –60 mV, membrane voltage was stepped to +20 mV, which elicited an inward current. N/OFQ (1 μM) inhibited this current. Partial recovery was obtained after washout of N/OFQ, and the recovered current was completely blocked by Cd2+ (200 μM, data not shown). (E) N/OFQ depresses cytoplasmic Ca2+ in Hcrt neurons. Representative trace demonstrating the effect of N/OFQ on Ca2+ fluorescence in transgenic orexin/YC2.1 mice in which Hcrt neurons express the calcium-sensing protein yellow cameleon 2.1. Ca2+ imaging from these mice revealed that N/OFQ inhibited approximately 65% of Hcrt neurons tested (18 of 28). (F) Concentration-dependent depression of cytoplasmic Ca2+ in Hcrt neurons induced by N/OFQ (mean ± SEM; n = 6–13 cells per concentration).