Orexin B (CAS 205640-91-1), also known as Hypocretin-2, is a synthetic 28-amino acid neuropeptide with a molecular weight of 2937.42 g/mol. Unlike Orexin A, Orexin B is a linear peptide with no intramolecular disulfide bridges and no pyroglutamyl modification. While Orexin A and Orexin B share 46% sequence homology within their C-terminal regions, their structural divergence leads to distinct receptor selectivity profiles. Produced via solid-phase peptide synthesis, Hypocretin-2 acts as an endogenous agonist with high selectivity for the OX2R receptor in preclinical neuroscience research.

Orexin B has been investigated as a ligand of the orexinergic system, and its differential receptor selectivity has been characterised for dissecting OX1R- versus OX2R-mediated signalling. In vitro receptor studies have characterised Orexin B downstream signalling at OX2R relative to OX1R in transfected cell line preparations, documenting the differential receptor selectivity profile of Orexin B compared with Orexin A and characterising OX2R-preferential calcium mobilisation as primary pharmacological readouts distinguishing Orexin B from its dual-receptor counterpart in pharmacological assays [1]. In vivo rodent studies have used Orexin B as a comparator tool to examine the relative contributions of OX1R and OX2R to sleep-wake regulation, arousal maintenance, and feeding behaviour, showing wake-inducing potency between Orexin A and Orexin B following direct administration in rats, characterising the OX2R-selective profile of Orexin B as a basis for dissecting receptor subtype-specific contributions to arousal state regulation and sleep-wake circuitry [2], making Orexin B a reference compound in orexin receptor pharmacology research as the OX2R-selective tool peptide for dissecting receptor subtype-specific contributions to sleep-wake regulation and arousal state transitions.

Orexin B is manufactured in a cGMP compliant laboratory to a guaranteed purity of 98% or above. Every batch is independently tested using HPLC and MS-UPLC analysis before dispatch. Vials are vacuum sealed and stored in a temperature controlled, monitored cold storage system. Certificates of Analysis are available on request.

Sold strictly for in vitro research purposes only. Not for human consumption. Intended for use by qualified researchers in laboratory settings only.

Editorial Team

Dr. Martina Rossi, PhD

Scientific Contributor and Reviewer

Reviewed and approved 14 June 2026

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