Sleep-deprivation regulates α-2 adrenergic responses of rat hypocretin/orexin neurons

• Published in: PloS one Vol. 6; no. 2; p. e16672
• Main Authors: Uschakov, Aaron, Grivel, Jeremy, Cvetkovic-Lopes, Vesna, Bayer, Laurence, Bernheim, Laurent, Jones, Barbara E, Mühlethaler, Michel, Serafin, Mauro
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 08.02.2011; Public Library of Science (PLoS)
• Subjects: Adrenergic alpha-2 Receptor Agonists - pharmacology; Adrenergic receptors; Animals; Baclofen; Barium; Biology; Brain; Brain - pathology; Brain slice preparation; Calcium; Calcium - metabolism; Calcium channels; Cell division; Channels; Clonidine; Clonidine - pharmacology; Deprivation; Desensitization; Dopamine; Down-regulation; G Protein-Coupled Inwardly-Rectifying Potassium Channels - metabolism; Inhibition; Intracellular Signaling Peptides and Proteins - metabolism; Medicine; Membrane Potentials - drug effects; Metabolism; Neurons; Neurons - drug effects; Neurons - metabolism; Neurons - pathology; Neuropeptides - metabolism; Neurosciences; Noradrenaline; Norepinephrine; Norepinephrine - metabolism; Orexins; Potassium; Potassium channels; Potassium channels (inwardly-rectifying); Proteins; Rats; Rats, Sprague-Dawley; Receptors, Adrenergic, alpha-2 - metabolism; Rodents; Sleep; Sleep deprivation; Sleep Deprivation - metabolism; Sleep Deprivation - pathology; Sleep disorders; Trends; γ-Aminobutyric acid B receptors
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0016672

We recently demonstrated, in rat brain slices, that the usual excitation by noradrenaline (NA) of hypocretin/orexin (hcrt/orx) neurons was changed to an inhibition following sleep deprivation (SD). Here we describe that in control condition (CC), i.e. following 2 hours of natural sleep in the morning, the α(2)-adrenergic receptor (α(2)-AR) agonist, clonidine, had no effect on hcrt/orx neurons, whereas following 2 hours of SD (SDC), it hyperpolarized the neurons by activating G-protein-gated inwardly rectifying potassium (GIRK) channels. Since concentrations of clonidine up to a thousand times (100 µM) higher than those effective in SDC (100 nM), were completely ineffective in CC, a change in the availability of G-proteins is unlikely to explain the difference between the two conditions. To test whether the absence of effect of clonidine in CC could be due to a down-regulation of GIRK channels, we applied baclofen, a GABA(B) agonist known to also activate GIRK channels, and found that it hyperpolarized hcrt/orx neurons in that condition. Moreover, baclofen occluded the response to clonidine in SDC, indicating that absence of effect of clonidine in CC could not be attributed to down-regulation of GIRK channels. We finally tested whether α(2)-ARs were still available at the membrane in CC and found that clonidine could reduce calcium currents, indicating that α(2)-ARs associated with calcium channels remain available in that condition. Taken together, these results suggest that a pool of α(2)-ARs associated with GIRK channels is normally down-regulated (or desensitized) in hcrt/orx neurons to only become available for their inhibition following sleep deprivation.