Summary
The stereospecific blockade by raclopride and FLB472 (the R enantiomer of raclopride) of the specific in vivo binding of [3H]-spiperone, [3H]-N,N-propylnorapomorphine (NPA) and [3H]-raclopride was studied in seven brain regions (e.g., caudate nucleus, olfactory tubercle, septum, hippocampus, frontal cortex, substantia nigra, pituitary gland) of the male albino rat. The binding of all three ligands was dose-dependently blocked by raclopride and FLB472. The blockade by FLB 472 occurred at doses 50–100 times higher than that obtained by raclopride. The maximal blockade by raclopride of [3H]-spiperone binding differed between brain areas. Thus, the largest blockade was obtained in the substantia nigra (95%), septum (90%), caudate nucleus (60%) and olfactory tubercle (60%), while the blockade of [3H]-spiperone binding in the frontal cortex and pituitary gland did not exceed 30% and 50%, respectively. In contrast to [3H]-spiperone, the in vivo binding of [3H]-NPA and [3H]-raclopride was prevented by 90–100% in all brain areas examined. Taken together, the present findings indicate that the in vivo binding of three radioactive ligands to a central dopamine D-2 receptor can be stereoselectively blocked by the enantiomers of raclopride. The findings suggest that, under in vivo conditions, [3H]-raclopride and [3H]-NPA may label a closely related receptor site. However only some of the [3H]-spiperone binding sites may be identical to the [3H]-raclopride binding sites. The findings indicate furthermore that the relative overlap of D-2 sites shared by [3H]-spiperone and [3H]-raclopride may vary between brain regions.
Similar content being viewed by others
References
Altar CA, Wasley AM, Neale RF, Stone GA (1986) Typical and atypical antipsychotic occupancy of D-2 and S-2 receptors: an autoradiographic analysis in rat brain. Brain Res Bull 16: 517–525
Barone D, Luzzani F, Assaudri A, Galliani G, Mennini T, Garattini S (1985) In vivo stereospecific [3H]-spiperone binding in the rat brain: characteristics, regional distribution, kinetics and pharmacological properties. Eur J Pharmacol 116: 63–74
Battaglia G, Titeler M (1982) [3H]N-n-propylnorapomorphine and [3H]spiperone binding in brain indicate two states of the D-2-dopamine receptor. Eur J Pharmacol 81: 493–498
Benakis A, Brown JPH, Benard P (1984) Autoradiography study of [14C]-sulpiride in monkey. Eur J Drug Metab Pharmacokinet 9: 365–370
Creese I, Schneider R, Snyder SH (1977) [3H]-Spiroperidol labels dopamine receptors in pituitary and brain. Eur J Pharmacol 46: 377–381
DeJesus OT, Revenaugh JR, Dinerstein RJ, Friedman AM (1984) In vivo binding of spiroperidol and bromospiroperidol at low drug loadings. Life Sci 35: 2165–2168
De Paulis T, Kumar Y, Johansson L, Rämsby S, Hall H, Sällemark M, Ängeby-Möller K, Ögren S-O (1986) Potential neuroleptic agents. 4. Chemistry, behavioural pharmacology and blocking of [3H]-spiperone binding of 3,5-disubstituted N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-methoxy-salicylamides. J Med Chem 29: 61–69
Dubois A, Scatton B (1985) Heterogenous distribution of dopamine D-2 receptors within the rat striatum as revealed by autoradiography of [3H]-N-n-propylnorapomorphine binding sites. Neurosci Lett 57: 7–12
Dubois A, Savasta M, Curet O, Scatton B (1986) Autoradiographic distribution of the D-1 agonist [3H]SKF38393, in the rat brain and spinal cord. Comparison with the distribution of D-2 dopamine receptors. Neuroscience 129: 125–137
Farde L, Ehrin E, Eriksson L, Greitz T, Hall H, Hedström C-G, Litton J-E, Sedvall G (1985) Substituted benzamides as ligands for visualization of dopamine receptor binding in the human brain by positron emission tomography. Proc Natl Acad Sci USA 82: 3863–3867
Florvall L, Ögren S-O (1982) Potential neuroleptic agents. 2,6-Dialkoxybenzamide derivatives with potent dopamine receptor blocking activities. J Med Chem 25: 1280
Fuxe K, Agnati LF, Köhler C, Kuonen D, Ögren S-O, Andersson K, Hökfelt T (1981) Characterization of normal and supersensitive dopamine receptors: effects of ergot drugs and neuropeptides. J Neural Transm 51: 3–37
Gawell L, Hall H, Köhler C (1985) Preparation of tritium labelled benzamide dopamine D-2 ligands at high specific activity. J Labelled Comp 22: 1033–1043
Gredal O, Nielsen M (1987) In situ molecular size of agonist dopamine D-2 binding sites in the rat striatum. J Neurochem 48: 364–369
Hall MD, Jenner P, Kelly E, Marsden CD (1983) Differential anatomical location of [3H]-N-n-propylnorapomorphine and [3H]-spiperone binding sites in the striatum and substantia nigra of the rat. Br J Pharmacol 79: 599–610
Hall MD, Jenner P, Marsden CD (1983) Differential labelling of dopamine receptors in rat brain in vivo: comparison of [3H]-piribedil, [3H]-S 3608, and [3H]-N,n-propylnorapomorphine. Eur J Pharmacol 87: 85–94
Hall H, Wedel I (1986) Comparisons between the in vitro binding of two substituted benzamides and two butyorphenones to dopamine D-2 receptors in the rat striatum. Acta Pharmacol Toxicol (Copenh) 58: 368–373
Jenner P, Marsden CD (1979) The substituted benzamides-a novel class of dopamine antagonists. Life Sci 25: 479–486
Köhler C, Ögren S-O, Haglund L, Ängeby T (1979) Regional displacement by sulpiride of [3H]-spiperone binding in vivo. Biochemical and behavioral evidence for a preferential action on limbic and nigral dopamine receptors. Neurosci Lett 13: 51–66
Köhler C, Fuxe K, Ross SB (1981a) Regional in vivo binding of [3H]N-n-propylnorapomorphine in the mouse brain. Evidence for labelling of central dopamine receptors. Eur J Pharmacol 72: 397–402
Köhler C, Haglund L, Ögren S-O, Ängeby K (1981b) Regional blockade by neuroleptic drugs of in vivo [3H]-spiperone binding in the rat brain. Relation to blockade of apomorphine induced hyperactivity and stereotypies. J Neural Transm 52: 163–173
Köhler C, Ögren S-O, Fuxe K (1984) Studies on the mechanism of action of substituted benzamide drugs. Acta Psychiatr Scand 69 [Suppl 311]: 125–137
Köhler C, Hall H, Ögren S-O, Gawell L (1985) Specific in vitro and in vivo binding of [3H]-raclopride, a potent substituted benzamide drug with high affinity for dopamine D-2 receptors in the rat brain. Biochemical Pharmacol 34: 2251–2259
Köhler C, Hall H, Gawell L (1986) Regional in vivo binding of the substituted benzamide [3H]-eticlopride in the rat brain. Evidence for the selective labelling of dopamine receptors. Eur J Pharmacol 120: 217–226
Köhler C, Fahlberg K (1985) Specific in vivo binding of [3H]-spiperone to individual lobes of the pituitary gland of the rat. Evidence for the labelling of dopamine receptors. J Neural Transm 63: 39–52
Köhler C, Radesäter A-C (1986) Autoradiographic visualization of dopamine D-2 receptors in the monkey brain using the selective benzamide drug [3H]-raclopride. Neurosci Lett 66: 85–90
Kuhar MJ, Murrin LC, Malouf AT, Klemm N (1978) Dopamine receptor binding in vivo: the feasibility of autoradiographic studies. Life Sci 22: 203–210
Laduron P, Leysen J (1977) Specific in vivo binding of neuroleptic drugs in rat brain. Biochem Pharmacol 26: 1003–1007
Leysen J, Gommeren W, Laduron PM (1978) Spiperone: a ligand of choice for neuroleptic receptors. 1. Kinetics and characteristics of in vitro binding. Biochem Pharmacol 27: 307–316
Leysen JE, Niemegeers EGE, Tollenaere JP, Laduron PM (1978) Serotonergic component of neuroleptic receptors. Nature 272: 168–171
Ljungberg T, Ungerstedt U (1978) Classification of neuroleptic drugs according to their ability to inhibit apomorphine-induced locomotion and gnawing: evidence for two different mechanisms of action. Psychopharmacology 56: 239–247
Magnusson O, Fowler CJ, Köhler C, Ögren S-O (1986) Dopamine D-2 receptors and dopamine metabolism. Relationship between biochemical and behavioural effects of substituted benzamide drugs. Neuropharmacology 25: 187–197
Morgan DG, Marcusson JO, Finch CE (1984) Contamination of serotonin-2 binding sites by an α1-adrenergic component in assays with [3H]spiperone. Life Sci 34: 2507–2514
Ögren S-O, Hall H, Köhler C, Magnusson O, Lindbom L-O, Ängeby T, Florvall L (1984) Remoxipride, a new potential antipsychotic compound with selective anti-dopaminergic actions in the rat brain. Eur J Pharmacol 102: 459–474
Ögren S-O, Hall H, Köhler C, Magnusson O, Sjöstrand S-E (1986) The selective dopamine D-2 receptor antagonist raclopride discriminates between dopamine mediated functions. Psychopharmacology 90: 287–294
Seeman P (1980) Brain dopamine receptors. Pharmacol Rev 32: 229–313
Sibley DR, Mahan LC, Creese I (1983) Dopamine receptor binding on intact cells. Absence of a high affinity agonist-receptor binding state. Mol Pharmacol 23: 295–302
Stefanini E, Devoto P, Marchisio AM, Varnaleone F, Callu R (1980) [3H]-spiroperidol binding to a putative dopaminergic receptor in rat pituitary gland. Life Sci 26: 583–587
van der Werf JF, van Het Schip F, Sebens JB, Korf J (1984) Quantification of in vivo spiperone binding in the rat striatum after lesions produced by kainate or decortication. Eur J Pharmacol 102: 387–399
van der Werf JF, Sebens JB, Korf J (1986) Tracer and maximal specific binding of tritiated spiperone or N-n-propylnorapomorphine to quantify dopamine receptors in rat brain in vivo. Life Sci 39: 155–160
Author information
Authors and Affiliations
Additional information
Raclopride is identical to ()-(S)-3,5,dichloro-N-(1-ethyl-2-pyrrolidinyl)methyl-6-methoxysalicylamide tartrate [FLA870()]. The (R) enantiomer of this compound will in the present paper be referred to as FLB472.
Rights and permissions
About this article
Cite this article
Köhler, C., Karlsson-Boethius, G. In vivo labelling of rat brain dopamine D-2 receptors. J. Neural Transmission 73, 87–100 (1988). https://doi.org/10.1007/BF01243380
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01243380