Hypocretin receptor expression in canine and murine narcolepsy models and in hypocretin-ligand deficient human narcolepsy.
OBJECTIVE
To determine whether hypocretin receptor gene (hcrtR1 and hcrtR2) expression is affected after long-term hypocretin ligand loss in humans and animal models of narcolepsy.


METHODS
Animal and human study. We measured hcrtR1 and hcrtR2 expression in the frontal cortex and pons using the RT-PCR method in murine models (8-week-old and 27-week-old orexin/ataxin-3 transgenic (TG) hypocretin cell ablated mice and wild-type mice from the same litter, 10 mice for each group), in canine models (8 genetically narcoleptic Dobermans with null mutations in the hcrtR2, 9 control Dobermans, 3 sporadic ligand-deficient narcoleptics, and 4 small breed controls), and in humans (5 narcolepsy-cataplexy patients with hypocretin deficiency (average age 77.0 years) and 5 control subjects (72.6 years).


RESULTS
27-week-old (but not 8-week-old) TG mice showed significant decreases in hcrtR1 expression, suggesting the influence of the long-term ligand loss on the receptor expression. Both sporadic narcoleptic dogs and human narcolepsy-cataplexy subjects showed a significant decrease in hcrtR1 expression, while declines in hcrtR2 expression were not significant in these cases. HcrtR2-mutated narcoleptic Dobermans (with normal ligand production) showed no alteration in hcrtR1 expression.


CONCLUSIONS
Moderate declines in hcrtR expressions, possibly due to long-term postnatal loss of ligand production, were observed in hypocretin-ligand deficient narcoleptic subjects. These declines are not likely to be progressive and complete. The relative preservation of hcrtR2 expression also suggests that hypocretin based therapies are likely to be a viable therapeutic options in human narcolepsy-cataplexy.
Mishima
Kazuo
K
Department of Psychiatry, Stanford University, Center for Narcolepsy, Palo Alto, CA, USA.
Fujiki
Nobuhiro
N
Yoshida
Yasushi
Y
Sakurai
Takeshi
T
Honda
Makoto
M
Mignot
Emmanuel
E
Nishino
Seiji
S
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D004285:Dogs; D005260:Female; D005625:Frontal Lobe / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression / Q000235:genetics; D005838:Genotype; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D008875:Middle Aged; D009290:Narcolepsy / Q000235:genetics* / Q000473:pathology; D009479:Neuropeptides / Q000172:deficiency; D064446:Orexin Receptors; D000068797:Orexins; D011149:Pons / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*; D018013:Receptors, Neuropeptide / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity
C578630:HCRTR1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide