Premium
[ 3 H]Neurokinin B and 125 I‐Bolton Hunter Eledoisin Label Identical Tachykinin Binding Sites in the Rat Brain
Author(s) -
Bergstrom L.,
Torrens Y.,
Saffroy M.,
Beaujouan J. C.,
Lavielle S.,
Chassaing G.,
Morgat J. L.,
Glowinski J.,
Marquet A.
Publication year - 1987
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1987.tb13136.x
Subject(s) - eledoisin , neurokinin b , neurokinin a , substance p , binding site , chemistry , population , medicine , endocrinology , receptor , stereochemistry , biology , biochemistry , neuropeptide , environmental health
[ 3 H]Neurokinin B ([ 3 H]NKB) of high specific activity (75 Ci/mmol) was synthesized for study of its binding to crude synaptosomes from the rat cerebral cortex. The specific binding of [ 3 H]NKB (75% of total binding) was temperature dependent, saturable, and reversible. Scatchard analyses and Hill plots showed the existence of a single population of noninteracting binding sites ( K D = 4.3 nM ; B max = 123 fmol/mg of protein). Competition studies indicated the following rank order of potencies among tachykinins: NKB > eledoisin (E) > kassinin > physalaemin > neurokinin A (NKA) > substance P (SP), a result suggesting that NKB might be the endogenous ligand for [ 3 H]NKB binding sites. It is of interest that 127 I‐Bolton Hunter (BH) NKA ( 127 I‐BHNKA) was much more potent than NKA in inhibiting the specific binding of [ 3 H]NKB, which raises certain questions concerning the use of 125 I‐BHNKA as a Iigand for NKA binding sites in the brain. These results, as well as those obtained with different SP analogues, show a close similarity to those obtained previously with 125 I‐BHE binding to cortical synaptosomes. This suggested that the two ligands labeled identical binding sites. In addition, using either [ 3 H]NKB or 125 I‐BHE as ligands, similar displacement curves were obtained with increasing concentrations of NKB and 127 I‐BHE. The similarity of the [ 3 H]NKB and 125 I‐BHE binding sites was further confirmed by comparison of their localization on rat brain sections by autoradiography. The distribution of binding sites for [ 3 H]NKB and 125 I‐BHE was identical throughout the brain, and the highest density of binding sites for the two ligands was found in layers IV and V of the cerebral cortex, the paraventricular nucleus of the hypothalamus (magnocellular part), and the ventral tegmental area.