The hypocretins, also known as orexins, are two neuropeptide transmitters produced exclusively by a few thousand neurons in the hypothalamus. Studies in mice, dogs and humans have shown that loss-of- function of the hypocretin system results in narcolepsy/cataplexy. We have recently shown that optical stimulation of genetically defined Hcrt neurons using the light activated cation channel, Channelrhodopsin 2 (ChR2) increases the probability of sleep-to-wake transitions. However, the role of Hcrt neurons in awake animals is still poorly understood. Here, we will use optogenetic manipulation of Hcrt neurons to test whether phasic activity of these neurons during wakefulness is sufficient to stabilize arousal. First, we will introduce ChR2 in Hcrt neurons using a lentivirus and we will use different photostimulation patterns to manipulate Hcrt neuronal activity during wakefulness to test whether sustained activity extends waking. We will monitor photostimulation-induced changes in Hcrt release by microdialysis. We will also monitor locomotor activity, anxiety, feeding, behavior and sleep/wake parameters. To determine the mechanism by which Hcrt induces wakefulness, we will optogenetically stimulate three of the main postsynaptic targets of the Hcrt system: noradrenergic neurons in the locus coeruleus, dopaminergic neurons in the ventral tegmental area, and cholinergic neurons in the basal forebrain. In a third specific aim, we will seek evidence demonstrating that blocking phasic activity during a few minutes under the appropriate conditions is sufficient to induce cataplexy in wild-type mice. Unlike pharmacological studies, optogenetics offers unprecedented millisecond scale temporal resolution, which allows vigilance state-specific analysis of neurotransmitter function in species with unconsolidated sleep such as rodents. Our data will expand the use of state-of-the-art optogenetic methods in sleep studies and will provide mechanistic models on how the hypocretinergic system stabilizes arousal. These experiments may also lead to new and enhanced treatments for narcolepsy, insomnia and other sleep disorders.

Public Health Relevance

Our data will expand the use of state-of-the-art optogenetic methods in sleep studies and will provide mechanistic models on how the hypocretinergic system stabilizes arousal. These experiments may also lead to new and enhanced treatments for narcolepsy, insomnia and other sleep disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Research Project (R01)
Project #
5R01MH087592-05
Application #
8604634
Study Section
Biological Rhythms and Sleep Study Section (BRS)
Program Officer
Vicentic, Aleksandra
Project Start
2010-06-10
Project End
2015-01-31
Budget Start
2014-02-01
Budget End
2015-01-31
Support Year
5
Fiscal Year
2014
Total Cost
$359,396
Indirect Cost
$136,646
Name
Stanford University
Department
Psychiatry
Type
Schools of Medicine
DUNS #
009214214
City
Stanford
State
CA
Country
United States
Zip Code
94305
Giardino, William J; de Lecea, Luis (2014) Hypocretin (orexin) neuromodulation of stress and reward pathways. Curr Opin Neurobiol 29:103-8
Tourino, Clara; Eban-Rothschild, Ada; de Lecea, Luis (2013) Optogenetics in psychiatric diseases. Curr Opin Neurobiol 23:430-5
Adamantidis, Antoine R; Tsai, Hsing-Chen; Boutrel, Benjamin et al. (2011) Optogenetic interrogation of dopaminergic modulation of the multiple phases of reward-seeking behavior. J Neurosci 31:10829-35
Carter, Matthew E; Yizhar, Ofer; Chikahisa, Sachiko et al. (2010) Tuning arousal with optogenetic modulation of locus coeruleus neurons. Nat Neurosci 13:1526-33