SLEEP 2011 Abstract Supplement

A. Basic Science I. Pharmacology and Biochemistry
0004
PHARMACOLOGICAL CHARACTERIZATION OF OREXIN
RECEPTOR ANTAGONISTS
Winrow CJ 1 , Doran SM 1 , Gotter AL 1 , Pausch MH 1 , Kuduk SD 2 ,
Uslaner J 1 , Carroll SS 1 , Smith S 1 , Coleman PJ 2 , Renger JJ 1
1
Neuroscience, Merck Research Laboratories, West Point, PA, USA,
2
Medicinal Chemistry, Merck Research Laboratories, West Point, PA,
USA
Introduction: Orexin/Hypocretin neuropeptides are responsible for regulating
wakefulness, signaling through the activation of two receptors,
Orexin 1 Receptor (OX1R) and Orexin 2 Receptor (OX2R). Genetic
and pharmacological studies have indicated that antagonism of Orexin
Receptors could provide benefit for insomnia and other disorders with
disruptions of the sleep/wake cycle. Merck has engaged in the discovery
and development of Dual Orexin Receptor Antagonists (DORAs) as
a novel treatment for primary insomnia, with the lead compound MK-
4305 currently in Phase III clinical studies.
Methods: The sleep promoting effects and detailed pharmacological
characterization of a series of small molecule DORAs will be presented.
MK-4305 and other DORAs were evaluated in vitro by determining potency
across species and by assessment of downstream signaling pathways,
and in vivo using microdialysis, receptor occupancy, locomotor,
sleep and quantitative EEG (qEEG) assays in wild-type and transgenic
animals.
Results: DORA compounds demonstrate similar affinity and potency
for orexin receptors from mice, rats, rabbits, dogs, rhesus and humans,
and show distinct effects on downstream signaling mechanisms. MK-
4305 and DORAs from different structural classes dose-dependently
occupy orexin receptors in vivo, decrease homecage locomotor activity
and reduce wake activity across species, while proportionally increasing
slow wave sleep and rapid eye movement sleep to increase total sleep
time. These sleep effects fundamentally differ from sedating GABAergic
drugs, and unlike zolpidem and diazepam, DORAs do not impair
rotarod performance even when administered at >10-fold above sleeppromoting
doses. DORA compounds also significantly attenuated histamine
and dopamine efflux in the rat brain. Sleep architecture and qEEG
patterns were consistent and dose-dependent across species, showing
modulation of low and high frequency spectral power bands.
Conclusion: Modulation of orexin/hypocretin signaling with a dual
orexin receptor antagonist effectively promotes sleep and provides a
novel approach for the treatment of insomnia.
Support (If Any): This project was supported by Merck.
0005
CHEMICAL CHAPERONE MODULATION OF AGE-
RELATED DECLINES IN RECOVERY SLEEP
Brown M, Naidoo N
Sleep Medicine, University of Pennsylvania, Philadelphia, PA, USA
Introduction: Alterations in the quality, quantity and architecture of
sleep and recovery sleep have been shown to occur during aging. The
fruit fly Drosophila melanogaster displays a sleep-like state that shares
several characteristics of mammalian sleep, including circadian and homeostatic
regulation. Studies have shown that sleep deprivation can lead
to an increase in misfolded/unfolded proteins, a process that is detrimental
to cell survival. Three hours of sleep deprivation in D. melanogaster
upregulates the unfolded protein response (UPR). This process reduces
the accumulation of misfolded/unfolded proteins and shields the cell
from injury. A key mechanism of the UPR involves increasing the levels
of endogenous chaperones that bind to misfolded proteins. The effectiveness
of this signaling pathway is diminished by the aging process.
Our laboratory has shown that increasing endogenous chaperone levels
enhances recovery sleep in D. melanogaster. These results lead to the
hypothesis that application of an exogenous chaperone could rescue agerelated
recovery sleep dysfunctions.
Methods: We compared total sleep, sleep bout number and average
bout duration in young (9 days) adult (8 week) and old (12 week) wildtype
Canton-S flies at baseline and after 6 h of sleep deprivation during
lights off from ZT18 to ZT24. Animals were treated with a chemical
chaperone for 48 h followed by baseline sleep recordings. Recovery was
recorded 24 h after sleep deprivation. Protein expression levels were
quantified for all groups.
Results: Significant (p