HCRTR2 and narcolepsy: Later, additional self-antigens, including the neuropeptide glutamic acid-isoleucine/a-melanocyte-stimulating hormone (NEI/aMSH) [83], the hypocretin receptor 2 (HCRTR2) [77], prostaglandin receptor D2 [84], and neurexin-1-alpha (NRXN1) [85], have been identified as targets of auto-Abs in narcolepsy patients.