[Michel Jouvet, from the discovery of paradoxical sleep and muscle atonia to the role of neuropeptides]

This article focuses on the contributions made by Michel Jouvet about the neurons responsible for generating the muscle atonia of paradoxical sleep (REM sleep). He was the first to describe the neurons responsible for muscle atonia during paradoxical sleep using "pontine" cats (in which the forebrain has been removed down to the pons) and localized pontine lesions. Also discussed is the research going on in the 1980s, when Michel Jouvet was hunting for the hypnogenic factor. At that time, he thought that it was secreted by the hypophysis; but this factor finally turned out to be controlled by the hypocretin/orexin and melanin concentrating hormone neurones located in the lateral hypothalamus. Several unforgettable moments with Michel Jouvet are described which occurred between 1983 and his last moments with us.

[Narcolepsy: From the discovery of a wake promoting peptide to autoimmune T cell biology and molecular mimicry with flu epitopes]

Narcolepsy-cataplexy was first described in the late 19th century in Germany and France. Prevalence was established to be 0.05 % and a canine model was discovered in the 1970s. In 1983, a Japanese study found that all patients carried HLA-DR2, suggesting autoimmunity as the cause of the disease. Studies in the canine model established that dopaminergic stimulation underlies anti-narcoleptic action of psychostimulants, while antidepressants were found to suppress cataplexy through adrenergic reuptake inhibition. No HLA association was found in canines. A linkage study initiated in 1988 revealed in hypocretin (orexin) receptor two mutations as the cause of canine narcolepsy in 1999. In 1992, studies on African Americans showed that DQ0602 was a better marker than DR2 across all ethnic groups. In 2000, hypocretin-1/orexin A levels were measured in the cerebrospinal fluid (CSF) and found to be undetectable in most patients, establishing hypocretin deficiency as the cause of narcolepsy. Decreased CSF hypocretin-1 was then found to be secondary to the loss of the 70,000 neurons producing hypocretin in the hypothalamus, suggesting immune destruction of these cells as the cause of the disease. Additional genetic studies, notably genome wide associations (GWAS), found multiple genetic predisposing factors for narcolepsy. These were almost all involved in other autoimmune diseases, although a strong and unique association with T cell receptor (TCR) alpha and beta loci were observed. Nonetheless, all attempts to demonstrate presence of autoantibodies against hypocretin cells in narcolepsy failed, and the presumed autoimmune cause remained unproven. In 2009, association with strep throat infections were found, and narcolepsy onsets were found to occur more frequently in spring and summer, suggesting upper away infections as triggers. Following reports that narcolepsy cases were triggered by vaccinations and infections against influenza A 2009 pH1N1, a new pandemic strain that erupted in 2009, molecular mimicry with influenza A virus was suggested in 2010. This hypothesis was later confirmed by peptide screening showing higher activity of CD4⁺ T cell reactivity to a specific post-translationally amidated segment of hypocretin (HCRT-_NH2) and cross-reactivity of specific TCRs with a pH1N1-specific segment of hemagglutinin that shares homology with HCRT-_NH2. Strikingly, the most frequent TCR recognizing these antigens was found to carry sequences containing TRAJ24 or TRVB4-2, segments modulated by narcolepsy-associated genetic polymorphisms. Cross-reactive CD4⁺ T cells with these cross-reactive TCRs likely subsequently recruit CD8⁺ T cells that are then involved in hypocretin cell destruction. Additional flu mimics are also likely to be discovered since narcolepsy existed prior to 2009. The work that has been conducted over the years on narcolepsy offers a unique perspective on the conduct of research on the etiopathogeny of a specific disease.

[Narcolepsy and Other 'Central Disorders of Hypersomnolence']

Narcolepsy and Other 'Central Disorders of Hypersomnolence' Abstract. 'Excessive daytime sleepiness', 'hypersomnia' in the sense of prolonged sleep need, 'tiredness' or 'fatigue' are frequent complaints in primary care, requiring a careful separation in view of a correct diagnostic. After exclusion of various internistic and neurologic causes by clinical and laboratory investigations and after exclusion of sleep apnoea syndrome or other causes of disturbed sleep by polysomnography, the ambiguous group of 'Central Disorders of Hypersomnolence' remains, including narcolepsy with and without cataplexy, idiopathic hypersomnia, and non-organic hypersomnia. Due to the important therapeutic consequences, these diseases must be differentiated and distinguished from insufficient sleep and from chronic fatigue syndrome, often requiring interdisciplinary diagnostics including objective assessment of the reported complaints.

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Zusammenfassung. Narkolepsie ist eine lebenslange Schlaf-Wach-Störung, charakterisiert durch exzessive Tagesschläfrigkeit und Episoden mit plötzlichem Muskeltonusverlust bei starken Emotionen (Kataplexie). Weitere Symptome sind Schlafparalyse, Halluzinationen und fragmentierter Nachtschlaf. Die Diagnose der Narkolepsie wird primär klinisch gestellt und durch zwei biologische Marker unterstützt: erstens durch Dokumentation von verfrühtem REM-Schlaf in der Schlaflaboruntersuchung, und zweitens durch Verlust des hypothalamischen Peptids Hypocretin in der Liquoruntersuchung. Ferner besteht eine genetische Prädisposition bei Positivität für das HLA DQB1*0602-Allel. Die Symptome der Narkolepsie können mit anderen psychiatrischen, neurologischen oder Schlaf-Wach-Störungen verwechselt werden. Die richtige Diagnosestellung ist entscheidend für die Einleitung einer wirksamen Therapie; gleichzeitig kann bei Patienten ohne Narkolepsie eine unnötige Behandlung mit psychoaktiven Substanzen, manche davon mit einem hohen Missbrauchsrisiko, vermieden werden.