title: [3H]neurokinin B and 125I-Bolton Hunter eledoisin label identical tachykinin binding sites in the rat brain.
abstract: [3H]Neurokinin B ([3H]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 [3H]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 (KD = 4.3 nM; Bmax = 123 fmol/mg of protein). Competition studies indicated the following rank order of potencies among tachykinins: NKB greater than eledoisin (E) greater than kassinin greater than physalaemin greater than neurokinin A (NKA) greater than substance P (SP), a result suggesting that NKB might be the endogenous ligand for [3H]NKB binding sites. It is of interest that 127I-Bolton Hunter (BH) NKA (127I-BHNKA) was much more potent than NKA in inhibiting the specific binding of [3H]NKB, which raises certain questions concerning the use of 125I-BHNKA as a ligand 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 125I-BHE binding to cortical synaptosomes. This suggested that the two ligands labeled identical binding sites. In addition, using either [3H]NKB or 125I-BHE as ligands, similar displacement curves were obtained with increasing concentrations of NKB and 127I-BHE. The similarity of the [3H]NKB and 125I-BHE binding sites was further confirmed by comparison of their localization on rat brain sections by autoradiography. The distribution of binding sites for [3H]NKB and 125I-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.
mesh_terms: D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D004600:Eledoisin / Q000031:analogs & derivatives* / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D007700:Kinetics; D008297:Male; D015287:Neurokinin B; D009479:Neuropeptides / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D018039:Receptors, Tachykinin; D013388:Succinimides / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism
chemical_list: C043034:Bolton Hunter-eledoisin ligand; D009479:Neuropeptides; D017981:Receptors, Neurotransmitter; D018039:Receptors, Tachykinin; D013388:Succinimides; D004600:Eledoisin; D015287:Neurokinin B