• Gene Information: OX1R and OX2R are encoded by the human HCRTR1 and HCRTR2 genes, respectively. Both belong to the class A rhodopsin-like G-protein-coupled receptor (GPCR) family. Sharing approximately 64% sequence identity, these paralogous genes arose via gene duplication, conserving key functional and structural transmembrane domains.
•  Protein Expression: OX1R and OX2R are predominantly expressed in the central nervous system. 
• Signaling Pathway: As GPCRs, OX1R and OX2R activate downstream intracellular cascades, modulating second messengers like calcium and cAMP to regulate neuronal activity. 
• Therapeutic Inhibition: Dual orexin receptor antagonists (DORAs), such as suvorexant and lemborexant, effectively treat insomnia by blocking wake-promoting pathways. Selective OX1R antagonists are investigated for treating addiction, anxiety, and compulsive disorders. Conversely, selective OX2R agonists are rapidly advancing as targeted disease-modifying therapies for narcolepsy type 1 to restore vigilance.

Gene targeting strategy for B-OX1R KO,OX2R KO mice. 

• The exons 1-7 of mouse Ox1r gene that encode the full-length protein were knocked out in B-OX1R KO,OX2R KO mice. 
• The exons 1-7 of mouse Ox2r gene that encode the full-length protein were knocked out in B-OX1R KO,OX2R KO mice.

Strain-specific analysis of Ox1r and Ox2r mRNA expression in wild-type C57BL/6 mice and B-OX1R KO,OX2R KO mice by RT-PCR. Brain RNA was isolated from wild-type C57BL/6 mice (+/+) and homozygous B-OX1R KO,OX2R KO mice (-/-), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse Ox1r and Ox2r primers.

Characterization of 24-hour sleep-wake profiles in B-OX1R KO,OX2R KO mice. (A) Schematic representation of the experimental design and timeline for electrophysiological monitoring. (B) Hourly temporal distribution of wake (left), non-rapid eye movement (NREM) sleep (middle), and rapid eye movement (REM) sleep (right) percentages across a 24-hour light-dark cycle in wild-type C57BL/6JNifdc and B-OX1R KO,OX2R KO mice. Shaded gray areas indicate the 12-hour dark phase. Values are expressed as mean ± SEM. Statistical significance was determined by two-way ANOVA. *P < 0.05, **P < 0.01, ***p < 0.001.

B-OX1R KO,OX2R KO mice display severe sleep fragmentation and direct wake-to-REM transitions without altering total sleep duration. (A) Total duration (in minutes) of Total Sleep Time (left), REM sleep time (middle), and NREM sleep time (right) over a 24-hour period in wild-type C57BL/6JNifdc mice and B-OX1R KO,OX2R KO mice. (B) Quantification of sleep-wake state transition frequencies during 24 hours. Values are expressed as mean ± SEM. Statistical significance was determined by two-way ANOVA. *P < 0.05, **P < 0.01, ***p < 0.001.