Differential modulation of 5-hydroxytryptamine1D binding sites by GTP and GTPgammaS.
Incubation of bovine caudate membranes with 10(-4) M GTP results in a competitive inhibition of 5-hydroxytryptamine1D (5-HT1D) receptor binding sites labeled by [3H]5-HT. By contrast, incubation of bovine caudate membranes with 10(-4) M GTPgammaS, a non-hydrolyzable analog of GTP, results in a decrease in both the apparent affinity (Kd) and density (Bmax) of 5-HT1D binding sites. The Kd is increased by 67 +/- 8%, (P less than 0.01, n = 12) while the Bmax is reduced by 52 +/- 10% in comparison with control values (P less than 0.05, n = 12). Pre-incubation studies indicate that GTPgammaS-induced changes in 5-HT1D receptors are persistent and time-dependent. These results indicate that GTPgammaS induces non-competitive changes in 5-HT1D receptor-G-protein interactions that are reflected as a decrease in the affinity and density of binding sites labeled by [3H]5-HT.
Department of Neurology, Stanford University Medical Center, CA 94304.
M A
MA
Harrington
S J
SJ
Peroutka
D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology*; D066298:In Vitro Techniques; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology*
D011985:Receptors, Serotonin; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate