Orexin-A Was Discovered Twice in the Same Year, and Neither Name Won
Most discovery stories come with one lab, one paper and one name.
Orexin-A doesn't. It was found in 1998 by two groups working independently, each of which named it, and both names are still in use.
Two papers, one molecule
One paper came from Sakurai and colleagues, published in Cell. They described a pair of peptides made in the hypothalamus, a region deep in the brain, and named them orexin-A and orexin-B.
They reported two further things. Both peptides derive from a single precursor, meaning one larger molecule that the two are cut from. And both act on two receptors of the G protein-coupled kind, a large class of receptors that sit on the surface of cells. They also localized that precursor to the lateral and posterior hypothalamus in rat brain.
The other came from de Lecea and colleagues, published in the Proceedings of the National Academy of Sciences. They described the same hypothalamic peptides and gave them a different name: the hypocretins.
Two groups, two journals, two names, one set of molecules. The source page for this compound says it in a single line: the two groups described the peptide independently in 1998, and both naming systems remain in use.
There is a quiet strength in that double origin. Two groups, working separately, reached the same hypothalamic peptides in the same year, so the discovery never rested on a single laboratory's result.
Even the titles read differently
The reference list on our research page carries both papers' full titles, and they are worth reading side by side.
The Cell paper describes a family of hypothalamic neuropeptides and receptors that regulate feeding behavior. The PNAS paper describes hypothalamus-specific peptides with neuroexcitatory activity.
Those are the papers' own words for what they had found, in the year they found it. Two groups looking at the same peptides arrived with two different first descriptions, and two different names to go with them.
A translation table that never went away
Naming contests usually end. One name gets adopted and the other survives in older papers.
This one never resolved. Orexin-A and hypocretin-1 are two names for one peptide, a 33-residue neuropeptide made in the hypothalamus.
The research page carries an FAQ entry that asks the obvious question: are orexin-A, hypocretin-1 and orexin-B the same thing? The first two are one peptide, described independently by two groups in 1998. The third, orexin-B, also called hypocretin-2, is a different peptide from the same precursor, with a different receptor preference. Evidence on orexin-B is not evidence on orexin-A.
Both names, inside the same body of work
The clearest sign that neither name won is in the measurement papers themselves.
The 2000 Lancet paper from Nishino and colleagues is titled "Hypocretin (orexin) deficiency in human narcolepsy," with both names in the title and one in parentheses. The Peyron paper in Nature Medicine refers to hypocretin peptides in its title. Mignot and colleagues' 2002 paper on spinal fluid measurement in Archives of Neurology puts hypocretin in its title too.
Our research page, describing the resulting marker, calls it orexin-A. The findings were published in one vocabulary and are summarized on this page in the other. Same peptide, two names, even inside the single most established use of it.
What the discovery turned into
A large body of measurement work grew out of these two papers, and it arrived quickly.
Two years after the discovery papers, Nishino and colleagues reported that hypocretin-1 was undetectable in the spinal fluid of most human patients with narcolepsy-cataplexy. Peyron and colleagues, the same year, found a generalized absence of hypocretin peptides in human narcoleptic brains examined after death, alongside one early-onset case carrying a mutation in the precursor. Mignot and colleagues then established measuring spinal fluid as a diagnostic test across narcolepsy and other hypersomnias, in 274 human subjects. Three papers, three different journals, all within four years of the discovery.
Low spinal fluid orexin-A is now the defining marker of narcolepsy type 1, and that finding is well replicated in humans. The research page describes this body of work as large, replicated and clinically entrenched.
One limit belongs with it, and it comes straight from the source. Those are measurement studies. They describe a peptide that is missing, and they do not test what giving one does. This piece makes no claim about that.
One molecule, two names, two numbers
There is one more place where the double history shows up, and it is a small, concrete one.
A CAS number is a registry identifier, a code assigned so that one number points to one chemical substance. Suppliers list orexin-A under one registry number, CAS 205640-90-0. The PubChem compound record for the same molecule carries a different one, CAS 205599-75-3. Both numbers designate orexin-A, so neither is wrong.
It would be tidy to say the two names produced the two numbers. The source page doesn't say that. It records the two facts side by side and leaves them unjoined, and so does this piece. What it does establish is narrower: the peptide has two names, it has two registry numbers, and a document quoting either number is describing the same peptide.
Two names from 1998, two numbers on file now, one molecule underneath. Our full research write-up covers what the published literature does and doesn't show about it.
Orexin-A is a research compound, supplied for laboratory research use only.