Distribution of cholecystokinin-like immunoreactivity in the rat main olfactory bulb

J Comp Neurol. 1985 Sep 22;239(4):373-83. doi: 10.1002/cne.902390403.


The anatomical localization of cholecystokinin-like immunoreactivity (CCK-I) within the rat main olfactory bulb was analyzed by using the peroxidase-antiperoxidase immunocytochemical technique. Neurons or neuronal processes containing CCK-I were localized within all laminae of the olfactory bulb except the olfactory nerve fiber layer. A large population of CCK-I neurons, with morphology, size, and distribution corresponding to that of the middle and external tufted cells, was observed within a zone extending from the deep periglomerular region through the superficial one-half to one-third of the external plexiform layer. A smaller number of immunoreactive perikarya were found in the deep external plexiform layer, the glomerular layer, and rarely within the inner plexiform layer. These CCK-I neurons appeared to correspond to internal tufted cells, periglomerular cells, and deep short-axon cells, respectively. Dense CCK-I staining of fibers and terminals was present within the internal plexiform layer and, less densely, within the neuropil of the granule cell layer. In addition, terminal-like CCK-I was localized within layer 1A of the anterior olfactory nucleus, the olfactory tubercle, and the most rostral piriform cortex. This observation provides corroboration for the identification of the principal CCK-I neuron in the rat olfactory bulb as the centrally projecting middle tufted cell. The present results, demonstrating the localization of CCK-I to both local circuit and projection neurons of the olfactory bulb and to terminal-like puncta in the internal plexiform and granule cell layers, suggest that CCK may be significantly involved in olfactory processing at several levels.

Publication types

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

MeSH terms

  • Animals
  • Axons / analysis
  • Brain Chemistry*
  • Cholecystokinin / analysis*
  • Cholecystokinin / immunology
  • Female
  • Immunoenzyme Techniques
  • Male
  • Nerve Endings / analysis
  • Neurons / analysis*
  • Olfactory Bulb / cytology*
  • Rats
  • Rats, Inbred Strains
  • Synapses / analysis
  • Tyrosine 3-Monooxygenase / immunology


  • Cholecystokinin
  • Tyrosine 3-Monooxygenase