Differential Distribution of orexin-A and orexin-B Immunoreactivity in the Rat Brain and Spinal Cord

Peptides. 1999 Dec;20(12):1455-70. doi: 10.1016/s0196-9781(99)00157-6.


The orexins are recently identified appetite-stimulating hypothalamic peptides. We used immunohistochemistry to map orexin-A and orexin-B immunoreactivity in rat brain, spinal cord, and some peripheral tissues. Orexin-A- and orexin-B-immunoreactive cell bodies were confined to the lateral hypothalamic area and perifornical nuclei. Orexin-A-immunoreactive fibers were densely distributed in the hypothalamus, septum, thalamus, locus coeruleus, spinal cord, and near the ventricles, but absent from peripheral sites investigated. In contrast, orexin-B-immunoreactive fibers were distributed sparsely in the hypothalamus. Orexin cells are strategically sited to contribute to feeding regulation, but their widespread projections suggest that orexins have other physiological roles.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibody Specificity
  • Brain / metabolism*
  • Carrier Proteins / chemistry
  • Carrier Proteins / metabolism*
  • Carrier Proteins / physiology
  • Eating / physiology
  • Hypothalamus / metabolism
  • Immunohistochemistry
  • Intracellular Signaling Peptides and Proteins*
  • Male
  • Molecular Sequence Data
  • Neuropeptides / chemistry
  • Neuropeptides / metabolism*
  • Neuropeptides / physiology
  • Orexins
  • Rats
  • Rats, Wistar
  • Spinal Cord / metabolism*
  • Tissue Distribution


  • Carrier Proteins
  • Intracellular Signaling Peptides and Proteins
  • Neuropeptides
  • Orexins