Trapping of labelled ligands in intact cells: A pitfall in binding studies

Dopamine D2 and D3 Receptor Occupancy in Normal Humans Treated with the Antipsychotic Drug Aripiprazole (OPC 14597) A Study Using Positron Emission Tomography and [11C]Raclopride

“…This was more recently further investigated by Vickery et al (1999). Consequently, Laruelle (2000) and Wong (2002) hypothesize that this could be the explanation for the paradoxical increase in spiperone binding following amphetamine administration, because the lipophilic spiperone is able to penetrate into the neuron, where it is trapped (Maloteaux et al 1983 (Barton et al 1991). This difference has been attributed to the different lipophilicity of the two tracers.…”

3H-spiroperidol binding to human peripheral mononuclear cells: Methodological aspects

“…On the other hand, the possibilky that this "binding site" might resemble one of the novel clopamine receptors (D3,4,5; Sokoloff et al 1990;Van Tel et al 1991;Sunahara et al 1991) could not be definitely excluded. The "nonGpeeific, nonsaturable" part might represent an unspecific uptake into the cells (Fleminger et al 1982;Maloteaux et al 1983).…”

Characteristics of the binding of [3H]‐mepyramine to intact human U373 MG astrocytoma cells: evidence for histamine‐induced H1‐receptor internalisation

“…The potential difficulties in using cell-permeable radioligands for the measurement of binding to cell surface receptors were documented some years ago (Maloteaux et al, 1983) and initially we set out to circumvent them by synthesizing a nonpenetrant radioligand for the histamine HI-receptor, Pfjl-QMDP, a quaternary amine, (Treherne & Young, 1988a), in analogy to the use of PH]-N-methylscopolamine (Galper et al, 1982) and CGP-12177 (Hertel et al, 1983a) (Chang et al, 1979;Hill & Young, 1981), and such sites are present, although not always recognised as such, in the DDT1MF2 (Mitsuhashi & Payan, 1988), HeLa (Raymond et al, 1991;Arias-Montafio & Young, 1993) and P19 (Bloemers et al, 1993) (Leurs et al, 1989), which appears to be a member of the cytochrome P450 family (Liu et al, 1992). However, this site was not evident in brain membranes (Liu et al, 1992) (Hertel et al, 1983a;Waldo et al, 1983) and muscarinic receptors (Koenig & Edwardson, 1994, and references therein).…”

“…Hunyady et 1991), brain slices (Quach et al, 1981;, acetylcholine (Koenig & Edwardson, 1994, and recells in culture (Taylor & Richelson, 1979;Brown et al, 1986; ferences therein) and noradrenaline (Leeb-Lunberg et al, 1987;Nakahata & Harden, 1987;Dillon-Carter & Chuang, 1989;Hausdorff et al, 1990). However, although there have been Cowlen et al, 1990;Smit et al, 1992;Bristow & 7amani, 1993; numerous studies of the mechanisms involved in the desensi- Dickenson & Hill, 1993;McCreath et al, 1994), a number of tization of responses to histamine at Hi-receptors in intestinal which have provided evidence for changes at the level of the smooth muscle (Barsoum & Gaddum, 1935;Cantoni & Eastreceptor (Brown et al, 1986;Nakahata & Harden, 1987;Hishinuma & Uchida, 1988;Cowlen et al, 1990;Horio et al, 1990b; Leurs et al, 1990;Dickenson & Hill, 1993) which will cross the cell membrane and bind to intracellular IkkW Joumal of Pharmacoloa (1995) 116, 2715-2723 sites and become concentrated in compartments with a low pH, have been noted some years ago (Maloteaux et al, 1983). We have attempted to avoid these difficulties by synthesizing a quaternary amine radioligand for the H1-receptor, [3H]-(+)-N-methyl-4-methyldiphenhydramine ([3H]-QMDP), which should bind only to sites on the plasma membrane (Treherne & Young, 1988a (Wallace & Young, 1983;Treherne & Young, 1988b), which should allow extensive washing of cells, and (b) the availability of non-penetrant and penetrant HI-receptor antagonists, which might be used to determine binding to plasma membrane HI-receptors and plasma membrane+ intracellularreceptors, respectively.…”