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Species differences in tachykinin receptor distribution: Further evidence that the substance P (NK 1 ) receptor predominates in human brain
Author(s) -
Rigby Michael,
O'Donnell Ruth,
Rupniak Nadia M.J.
Publication year - 2005
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20664
Subject(s) - eledoisin , tachykinin receptor , receptor , neurokinin b , biology , marmoset , substance p , neurokinin a , endocrinology , medicine , human brain , gerbil , central nervous system , neuropeptide , neuroscience , biochemistry , paleontology , ischemia
Marked species differences in the distribution of central tachykinin receptors are reported but uncertainty remains about the ability of available ligands to detect NK 2 and NK 3 receptors in human brain. We compared the distribution of NK 1 , NK 2 , and NK 3 receptors in sections from rodent, primate, and human brain using the 125 I‐labeled ligands substance P (SP) for the NK 1 receptor, neurokinin A (NKA) for the NK 2 receptor, and neurokinin B (NKB) and eledoisin for NK 3 receptors. Duration of exposure to autoradiographic film was from 7 days for [ 125 I]SP up to 90 days for the other ligands. High levels of specific [ 125 I]SP binding were seen throughout the brains of all species studied. Specific [ 125 I]NKA binding was detected in brains from neonatal rat, and to a lesser level in adult rat, gerbil, and guinea pig; it was not detected in monkey or human brain, but was present in circular muscle of human duodenum, confirming that this ligand binds to human NK 2 receptors under our experimental conditions. Specific [ 125 I]NKB and [ 125 I]eledoisin binding was widespread in brain sections from rats, gerbils, and guinea pigs, and very low levels were also detected in marmoset, squirrel monkey, and rhesus monkey brain after prolonged (up to 90 days) exposure. We failed to identify specific eledoisin binding in human brain, even after prolonged exposures. These findings demonstrate that the NK 1 receptor is the predominant tachykinin receptor expressed in primate and human brain, but that low levels of NK 3 receptor are present in nonhuman, primate brain. J. Comp. Neurol. 490:335–353, 2005. © 2005 Wiley‐Liss, Inc.