1. Narcolepsy
Deb Perkins-Hicks

2. Narcolepsy: Neural Mechanisms of Sleepiness and Cataplexy
Christian R. Burgess and Thomas E. Scammell
Narcolepsy: Neural Mechanisms of Sleepiness and Cataplexy

3. What is Narcolepsy?
Chronic brain disorder causing fragmented wakefulness
1 in 2,000 people
Adolescence
Average 10 years to diagnosis

4. Symptoms Fall asleep even when fully involved in an activity
Mental cloudiness
Lack of energy
Extreme exhaustion
Atonia or sleep paralysis
Hallucinations
Microsleep
Disturbed sleep
Cataplexy

5. Causes Deficiency or absence of Oxexin Genetics HLA DQB1(*)0602 gene
90% of the orexin-producing neurons are lost in human narcolepsy with cataplexy
Genetics
HLA DQB1(*)0602 gene
TCR-alpha gene
20-40 times higher risk if family member has narcolepsy

6. Proposed causes Disruption of circadian rhythm Streptococcal infection
Autoimmune

7. Normal sleep cycle 8 hours 4-6 sleep cycles
100 to 110 min. long
NREM to REM sleep after 80 to 100 min.
Circadian rhythm

8. Narcolepsy sleep cycle
Excessive daytime sleepiness
Periods of drowsiness every 3-4 hours
NREM to REM sleep within a few min.
Circadian rhythm close to normal
May feel well rested upon awakening

9. Cataplexy Sudden muscle weakness Triggered by emotions
Few seconds to minutes
Weaken only eyelids and face or the whole body
Attacks can recur repeatedly for hours or days

10. Atonia pathways

11. Atonia pathways

14. Orexin Neurons Suppress Narcolepsy Via 2 Distinct Efferent Pathways
Emi Hasegawa, Masashi Yanagisawa, Takeshi Sakurai, and Michihiro Mieda
Orexin Neurons Suppress Narcolepsy Via 2 Distinct Efferent Pathways

15. Orexin innervations of monoaminergic and cholinergic neurons
Locus Coeruleus (LC) Noradreneric neurons
Dorsal raphe nucleus (DR) serotonergic neurons
Median raphe nucleus (MnR) serotonergic neurons
Tuberomammillary nucleus (TMN) histaminergic neurons
Laterodorsal tegmental nucleus (LDT) cholinergic neurons
Pedunculopontine tegmental nucleus (PPT) cholinergic neurons

17. Narcoleptic phenotype mice
Phenotypes similar to human narcolepsy:
orexin-/-mice – targeted deletion of prepro-orexin gene (exhibit fragmentation of sleep and cataplexic like behavior)
orexin/ataxin-3 mice – orexin neurons specifically ablated
Ox1r-/-Ox2r-/- mice – lack both orexin receptors

18. Search for wake-active monoaminergic/cholinergic nuclei that mediate the suppression of narcoleptic symptoms by orexin neurons

19. Recombinant adeno-associated viruses generated to express OX1R or OX2R
Ox1r-/-Ox2r-/- mice
Phenotype resembles narcolepsy in the dark phase
Fragmented wakefulness
Cataplexy
Shortened REM sleep latency
Excessive REM sleep time
Recombinant adeno-associated viruses generated to express OX1R or OX2R
Recorded EEG/EMG to score sleep/wakefulness states

20. Dorsal raphe
Aav-EF1α/OX2R::EGFP

21. Locus coeruleus
AAV-EF1α/OX1R::EGFP

22. Tuberomammillary
AVV-EF1α/OX2R::EGFP

23. Pedunculopontine tegmental
AVV-EF1α/OX1R::EGFP

24. Restoration of OX2R in DR prevents cataplexy-like episodes
LC, TMN, PPT – little or no change

25. DR - increased REM sleep with little change in latency
LC - REM sleep latency with little change in sleep time

26. Restoration of OX1R in LC improved wakefulness and reduced wakefulness episodes
DR, TMN, PPT – little or no change

27. Pearson correlation analysis
Compared the number of cells with restored orexin receptor expression to the amount of change in narcoleptic symptoms
Neuronal population DR LC

30. Result DR
Inhibition of cataplexy-like episodes highly correlated with the number of EGFP+ TPH+ cells
Little correlation with the number of EGFP+TPH- cells LC
Wakefulness episodes highly correlated with the number EGFP+TH+ cells
Little correlation with the number of EGFP+TH-cells

31. Restoration of orexin receptors in DR or LC using neuron type-selective promoter
Targeted serotonergic neurons to express OX2R
Targeted nonadrenergic neurons to express OX1R

36. OX2R expression in Serotonergic neurons
OX1R expression in Noradrenergic neurons

37. Pharmacogenic activation of DR serotonergic and LC noradrenergic neurons in narcoleptic mice

38. Artificial activation of
DR serontonergic neurons
LC noradrenergic neurons
Orexin/ataxin-3 mice – orexin neurons ablated postnatally
DREADD technology used to mutate muscarinic receptors
Clozapine-N-oxide (CNO)
AAV-Pet 1/hM3Dq microinjected into DR
AAV-PRSx8/hM3Dq microinjected into LC

43. Sawako Tabuchi, Tomomi Tsunematsu, Sarah W
Sawako Tabuchi, Tomomi Tsunematsu, Sarah W. Black, Makoto Tominaga, Megumi Maruyama, Kazuyo Takagi, Yasuhiko Minokoshi, Takeshi Sakurai, Thomas S. Kilduff, and Akihiro Yamanaka
Conditional Ablation of Orexin/Hypocretin Neurons: A New Mouse Model for the Study of Narcolepsy and Orexin System Function

44. Current animal models lack
Orexin peptides
Orexin receptors
Orexin neurons
Congenital vs. later onset
Infrequent cataplexy events

45. Creation of the orexin-tTA:TetO DTA mice (robust cataplexy, disrupted sleep and weight gain)

46. Removal of DOX from diet

47. Cont.
Orexin neurons in lateral hypothalamus decreased faster than the medial population
Loss of orexin cell bodies in hypothalamus
Decrease in orexin neuron nerve endings in DR and LC
Noradrenergic and serotonergic neurons not altered

48. Melanin Concentrating Hormone neurons unaffected by DOX removal

49. MCH

50. Microglial cells activated

54. Partial ablation of orexin neurons and cataplexy bout frequency

57. Diurnal distribution of cataplexy bouts as orexin neurons degenerate
Bouts greater during first half of dark period
Increased during last 2 h of light period

61. Partial lesion of orexin neurons induced by manipulation of DOX chow availability

67. Metabolic measurements in orexin-tTA; TetO DTA mice

73. THE END