0280 Orexins play a dual role in immobility episodes on taiep rats a model of H-ABC

Abstract

Abstract Introduction Leukodystrophies are a heterogenous group of congenital myelin alterations with more than 30 classified diseases was described until now. Among them there are several mutations in the a and b tubulins the so called tubulinophaties, that affect the central nervous system. The hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC) is due to a mutation in the tubulin b 4a (TUBB4A) and the taiep rats is the only available model of this human disease with similar magnetic resonance changes and a punctual mutation in the TUBB4A. Taiep rats had immobility episodes (IEs) with a peak between at 9 months of age. Importantly, electroencephalographic recordings shown that IEs had a rapid eye movement (REM) sleep characteristic pattern supporting that are equal to human cataplexy episodes that are key sign of narcolepsy. It is possible to induced IEs when taiep rats are manipulated from the tail or the thorax. Narcolepsy in humans and narcoleptic dogs had a significant decreased in orexin levels in the cerebrospinal fluid (CSF) and a concomitantly decreased of orexin neurons in the lateral hypothalamus. Methods We used 21 male rats from taiep at 9 months of age. All rats were kept in standard conditions and were implanted for EEG, EMG and EOG recordings to characterize IEs. We administered orexin A and B agonists and characterized the sleep-wake cycle and frequency of IEs, the peptides were administered by a intracerebroventricular (i.c.v.) injections diluted in artificial CSF. We also measured the number or positive orexin neurons in the lateral hypothalamus through immunohistochemistry. Results The i.c.v. administration of [Ala11, D-Leu 15] orexin B agonist significantly decrease the frequency of IEs with 3 and 10 nM doses (P≤0.05 and P≤0.03, respectively), without affecting the sleep-wake pattern. However, the i.c.v. administration of Orexin A (17-33) an agonist did not affect the sleep-wake pattern or the frequency of IEs. It is relevant that the number of orexins neurons did not differ between taiep and control Sprague-Dawley (SD) male rats. Conclusion Our results showed that IEs had a REM sleep EEG characteristic pattern with cataplexic-like atonia, there are sensible to orexin B agonist, but the number of orexin positive neurons do not differ with respect to SD male rats. In conclusion taiep rats a model of H-ABC is an adequate model of cataplexy-like episodes due to myelin disease. Support (If Any) Partially supported by PRONACES-CONACYT grant 194171, and VIEP-BUAP 2021 to CA in Neuroendocrinología. KGE is fellowship from CONACYT No. 772626.