Further demonstration that [Pro9]-substance P is a potent and selective ligand of NK-1 tachykinin receptors.
Previous studies have indicated that [Pro9]-substance P ([Pro9]-SP) possesses very good affinity for NK-1 binding sites and that, in contrast to substance P, it interacts selectively with these sites. Therefore, [3H][Pro9]-SP (75 Ci/mmol) was synthesized in order to study its binding to membranes of the rat brain. Specific binding of [3H][Pro9]-SP (75% of total binding) was temperature-dependent, saturable, and reversible. Scatchard analysis and Hill plots revealed the existence of a single population of noninteracting binding sites (KD and Bmax values: 1.48 nM and 29.7 fmol/mg of protein, respectively). Competition studies with several tachykinins and analogues indicated that the pharmacological profile of [3H][Pro9]-SP binding sites is identical to that of NK-1 binding sites. Rat brain sections labeled with either [3H][Pro9]-SP or [3H]SP, revealed a close similarity in the topographical distribution of [3H][Pro9]-SP and [3H]SP binding sites. Biochemical, pharmacological, and autoradiographic data obtained with [3H][Pro9]-SP did not provide any evidence for the existence of subtypes of NK-1 binding sites. [Pro9]-SP had neither agonist nor antagonist properties on NK-2 and NK-3 receptors. Indeed, it did not stimulate phosphoinositide turnover on the hamster urinary bladder (NK-2 assay) and was devoid of activity on the contraction of the rabbit pulmonary artery (NK-2 assay) and of the rat portal vein (NK-3 assay). As a result of its high selectivity, [Pro9]-SP thus appears an excellent tool for investigating the functional properties of NK-1 receptors.
Petitet
F
F
Collège de France, INSERM U 114, Paris.
Beaujouan
J C
JC
Saffroy
M
M
Torrens
Y
Y
Chassaing
G
G
Lavielle
S
S
Besseyre
J
J
Garret
C
C
Carruette
A
A
Glowinski
J
J
D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008297:Male; D008566:Membranes / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D018039:Receptors, Tachykinin; D013373:Substance P / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D013388:Succinimides / Q000378:metabolism; D015320:Tachykinins / Q000378:metabolism / Q000494:pharmacology; D014018:Tissue Distribution
C043194:Bolton Hunter reagent-substance P conjugate; D008024:Ligands; D017981:Receptors, Neurotransmitter; D018039:Receptors, Tachykinin; D013388:Succinimides; D015320:Tachykinins; C067285:substance P, Pro(9)-; D013373:Substance P