Orexin A-like immunoreactivity in the rat brain

Neurosci Lett. 1999 Feb 5;260(3):161-4. doi: 10.1016/s0304-3940(98)00977-x.


Distribution of orexin-A-like immunoreactivity (ORX-LI) in rat brains was investigated with the use of a rabbit polyclonal antibody against the full length peptide orexin A. Virtually all the ORX-LI cell bodies were observed in the lateral hypothalamus at the level of median eminence. The large majority of ORX-LI neurons appeared spherical or fusiform, 20-30 microm in diameter and issued two to five cell processes with few secondary branchings. Numerous ORX-LI fibers were observed in subregions of the hypothalamus. ORX-LI cell processes were sparsely distributed in the cortex, hippocampus and thalamus. Many varicose ORX-LI cell processes were situated close to the 3rd and lateral ventricles, some of which appeared to be protruding into the lumen. As a corollary, orexin A may be released into the ventricles and interact with neurons in distant targets, in addition to influencing the activity of neurons with which ORX-LI axons make synaptic contacts.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / metabolism
  • Brain / anatomy & histology
  • Brain / cytology
  • Brain Chemistry / physiology*
  • Carrier Proteins / metabolism*
  • Cell Size
  • Female
  • Immunohistochemistry
  • Intracellular Signaling Peptides and Proteins*
  • Male
  • Nerve Fibers / metabolism
  • Neurons / metabolism
  • Neurons / ultrastructure
  • Neuropeptides / metabolism*
  • Orexins
  • Rats
  • Rats, Sprague-Dawley
  • Synapses / metabolism


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