The study examines the expression pattern of mRNA encoding two orexin receptors (OX1R and OX2R) in the rat brain. OX1R mRNA is most abundant in the ventromedial hypothalamic nucleus (VMH), while OX2R mRNA is predominantly expressed in the paraventricular nucleus (PVN). High levels of OX1R mRNA are also detected in the tenia tecta, hippocampal formation, dorsal raphe, and locus coeruleus. OX2R mRNA is mainly expressed in the cerebral cortex, nucleus accumbens, subthalamic and paraventricular thalamic nuclei, and the anterior pretectal nucleus. The widespread distribution of orexin receptors suggests multiple functions for orexins, including feeding regulation and other neuroendocrine functions. The divergent distribution of OX1R and OX2R indicates that these receptors may mediate distinct functions for orexins.The study examines the expression pattern of mRNA encoding two orexin receptors (OX1R and OX2R) in the rat brain. OX1R mRNA is most abundant in the ventromedial hypothalamic nucleus (VMH), while OX2R mRNA is predominantly expressed in the paraventricular nucleus (PVN). High levels of OX1R mRNA are also detected in the tenia tecta, hippocampal formation, dorsal raphe, and locus coeruleus. OX2R mRNA is mainly expressed in the cerebral cortex, nucleus accumbens, subthalamic and paraventricular thalamic nuclei, and the anterior pretectal nucleus. The widespread distribution of orexin receptors suggests multiple functions for orexins, including feeding regulation and other neuroendocrine functions. The divergent distribution of OX1R and OX2R indicates that these receptors may mediate distinct functions for orexins.