Neuronal activity of orexin and non-orexin waking-active neurons during wake–sleep states in the mouse

doi:10.1016/j.neuroscience.2008.02.058

Neuroscience

Volume 153, Issue 3, 15 May 2008, Pages 860-870

https://doi.org/10.1016/j.neuroscience.2008.02.058 Get rights and content

Abstract

Using extracellular single unit recordings alone or in combination with neurobiotin juxtacellular labeling and orexin (hypocretin) immunohistochemistry in the mouse, we have recorded a total of 452 neurons in the orexin neuron field of the posterior hypothalamus. Of these, 76 exhibited tonic discharge highly specific to wakefulness, referred to as waking-active neurons. They showed differences from each other in terms of spike shape, activity profile, and response to an arousing sound stimulus and could be classified into three groups on the basis of spike shape as: 1) biphasic broad; 2) biphasic narrow; and 3) triphasic. Waking-active neurons characterized by biphasic broad spikes were orexin-immunopositive, whereas those characterized by either biphasic narrow or triphasic broad spikes were orexin-immunonegative. Unlike waking-specific histamine neurons, all orexin and non-orexin waking-active neurons exhibited slow (<10 Hz) tonic discharges during wakefulness and ceased firing shortly after the onset of electroencephalogram (EEG) synchronization (deactivation), the EEG sign of sleep (drowsy state). They remained virtually silent during slow-wave sleep, but displayed transient discharges during paradoxical (or rapid eye movement) sleep. During the transition from sleep to wakefulness, both orexin and triphasic non-orexin neurons fired in clusters prior to the onset of EEG activation, the EEG sign of wakefulness, and responded with a short latency to an arousing sound stimulus given during sleep. In contrast, the biphasic narrow non-orexin neurons fired in single spikes either prior to, or after, EEG activation during the same transition and responded to the stimulus with a longer latency. The activity of all waking-active neurons preceded the return of muscle tonus at the transition from paradoxical sleep to wakefulness. These data support the view that the activity of orexin and non-orexin waking-active neurons in the posterior hypothalamus plays an important wake-promoting role and that their activity antagonizes cortical deactivation and loss of muscle tone.

Section snippets

Animals and surgery

All procedures were approved by the University of Lyon 1 Animal Care Committee, whose standards meet those of the EEC Guidelines (86/609/EEC) and the Policy on Ethics approved by the Society for Neuroscience (1993). All efforts were made to minimize the number of animals used and their suffering.

Thirty-nine male adult C57BL/6 mice (Harlan France SARL (Le Malcourlet, Gannat, France) 28–35 g at the time of surgery) were used. The mice were anesthetized with ketamine/xylazine (80/10 mg kg-1, i.p.)

Results

Extracellular recordings were made from a total of 452 neurons in the Orx/Hcrt neuron field of the posterior hypothalamus of 39 mice during the complete sleep–wake cycle, including at least one episode of PS. As shown in Fig. 1, Orx/Hcrt neurons were distributed in the dorsolateral region of the posterior hypothalamus, the region located dorsal and rostral to the tuberomamillary nuclei (TM) containing HA neurons. Of 452 neurons recorded, 76 exhibited tonic discharge highly specific to W and are

Discussion

For the first time in non-anesthetized, head-restrained mice, we have identified, in the posterior hypothalamus, one group of Orx/Hcrt waking-active neurons and two groups of non-Orx/Hcrt waking-active neurons which may play an important role in both the induction and maintenance of W.

Conclusion

In conclusion, the present findings in non-anesthetized, head-restrained mice support the view that Orx/Hcrt and non-Orx/Hcrt waking-active neurons in the posterior hypothalamus play an important wake-promoting role and that their coordinated activity antagonizes cortical deactivation and loss of postural muscle tone.

Acknowledgments

The present study was supported by INSERM U628, Claude Bernard University and European Contract No. QLRT-2001-00826 (5th PCRDT). K. Takahashi was supported by grants from the Fyssen Foundation.

References (48)

R.M. Chemelli et al.
Narcolepsy in orexin knockout mice: molecular genetics of sleep regulation
Cell
(1999)
J. Hara et al.
Genetic ablation of orexin neurons in mice results in narcolepsy, hypophagia, and obesity
Neuron
(2001)
T. Ichikawa et al.
Localization of two cholinergic markers, choline acetyltransferase and vesicular acetylcholine transporter in the central nervous system of the rat: in situ hybridization histochemistry and immunohistochemistry
J Chem Neuroanat
(1997)
B.E. Jones
From waking to sleeping: neuronal and chemical substrates
Trends Pharmacol Sci
(2005)
Y. Koyama et al.
In vivo electrophysiological distinction of histochemically-identified cholinergic neurons using extracellular recording and labelling in rat laterodorsal tegmental nucleus
Neuroscience
(1998)
Y. Koyama et al.
State-dependent activity of neurons in the perifornical hypothalamic area during sleep and waking
Neuroscience
(2003)
Y. Li et al.
Hypocretin/orexin excites hypocretin neurons via a local glutamate neuron: A potential mechanism for orchestrating the hypothalamic arousal system
Neuron
(2002)
J.S. Lin
Brain structures and mechanisms involved in the control of cortical activation and wakefulness, with emphasis on the posterior hypothalamus and histaminergic neurons
Sleep Med Rev
(2000)
J.S. Lin et al.
A critical role of the posterior hypothalamus in the mechanisms of wakefulness determined by microinjection of muscimol in freely moving cats
Brain Res
(1989)
L. Lin et al.
The sleep disorder canine narcolepsy is caused by a mutation in the hypocretin (orexin) receptor 2 gene
Cell
(1999)

S. Nishino

The hypothalamic peptidergic system, hypocretin/orexin and vigilance control

Neuropeptides

(2007)

S. Nishino et al.

Decreased brain histamine content in hypocretin/orexin receptor-2 mutated narcoleptic dogs

Neurosci Lett

(2001)

S. Nishino et al.

Hypocretin(orexin) deficiency in human narcolepsy

Lancet

(2000)

D. Pinault

A novel single-cell staining procedure performed in vivo under electrophysiological control: morpho-functional features of juxtacellular labeled thalamic cells and other central neurons with biocytin or Neurobiotin

J Neurosci Methods

(1996)

T. Sakurai

Roles of orexin/hypocretin in regulation of sleep/wakefulness and energy homeostasis

Sleep Med Rev

(2005)

M. Sallanon et al.

Long-lasting insomnia induced by preoptic neuron lesions and its transient reversal by muscimol injection into the posterior hypothalamus in the cat

Neuroscience

(1989)

C.B. Saper et al.

The sleep switch: hypothalamic control of sleep and wakefulness

Trends Neurosci

(2001)

D.R. Stevens et al.

The mechanism of spontaneous firing in histamine neurons

Behav Brain Res

(2001)

H. Tago et al.

Distribution of choline acetyltransferase-containing neurons of the hypothalamus

Brain Res

(1987)

T.C. Thannickal et al.

Reduced number of hypocretin neurons in human narcolepsy

Neuron

(2000)

A. Yamanaka et al.

Orexins activate histaminergic neurons via the orexin 2 receptor

Biochem Biophys Res Commun

(2002)

L. Bayer et al.

Orexins (hypocretins) directly excite tuberomammillary neurons

Eur J Neurosci

(2001)

A. Crocker

Concomitant loss of dynorphin, NARP, and orexin in narcolepsy

Neurology

(2005)

E. Eggermann et al.

The wake-promoting hypocretin-orexin neurons are in an intrinsic state of membrane depolarization

J Neurosci

(2003)

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Systems neuroscienceNeuronal activity of orexin and non-orexin waking-active neurons during wake–sleep states in the mouse

Abstract

Section snippets

Animals and surgery

Results

Discussion

Conclusion

Acknowledgments

Cell

Neuron

J Chem Neuroanat

Trends Pharmacol Sci

Neuroscience

Neuroscience

Neuron

Sleep Med Rev

Brain Res

Cell

Neuropeptides

Neurosci Lett

Lancet

J Neurosci Methods

Sleep Med Rev

Neuroscience

Trends Neurosci

Behav Brain Res

Brain Res

Neuron

Biochem Biophys Res Commun

Orexins (hypocretins) directly excite tuberomammillary neurons

Eur J Neurosci

Concomitant loss of dynorphin, NARP, and orexin in narcolepsy

Neurology

The wake-promoting hypocretin-orexin neurons are in an intrinsic state of membrane depolarization

J Neurosci

Systems neuroscience
Neuronal activity of orexin and non-orexin waking-active neurons during wake–sleep states in the mouse