Visualization of neurokinin-3 receptor sites in rat brain using the highly selective ligand [3H]senktide.
The autoradiographic distribution of the neurokinin (NK)-3 receptor sub-type was visualized in the rat brain using [3H]senktide, a highly selective ligand, [3H]Senktide apparently binds to a single class of high affinity (Kd = 2.8 +/- 1.0 nM), low capacity (Bmax = 31.2 +/- 3.0 fmol/mg protein) sites in rat brain cortex. The ligand selectivity pattern reveals that eledoisin and senktide are potent competitors of both [3H]senktide and [125I]Bolton-Hunter eledoisin binding sites demonstrating the NK-3 nature of these sites. Autoradiographic data show that [3H]senktide binding sites are concentrated in mid-cortical layers, supraoptic nucleus, zona incerta, basolateral nucleus of the amygdala and interpeduncular nucleus. Much lower densities of binding are seen in most other areas such as the caudate-putamen and cerebellum. This distribution is similar, but not identical, to that previously reported for NK-3 sites using less selective ligands. It is most likely because less selective probes also bind to other classes of NK receptors. The higher selectivity of [3H]senktide is thus an important advantage for the precise characterization of NK-3 receptor binding parameters.
Douglas Hospital Research Centre, McGill University, Verdun, Qué., Canada.
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D000818:Animals; D001345:Autoradiography; D002540:Cerebral Cortex / Q000378:metabolism*; D008297:Male; D010446:Peptide Fragments / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018042:Receptors, Neurokinin-3; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D013373:Substance P / Q000031:analogs & derivatives* / Q000378:metabolism
D010446:Peptide Fragments; D018042:Receptors, Neurokinin-3; D017981:Receptors, Neurotransmitter; C054724:senktide; D013373:Substance P