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PubMed1980

In vivo [3H]spiperone binding to the rat hippocampal formation: involvement of dopamine receptors.

The existence of DA receptors in the rat hippocampus was demonstrated with an in vivo [3H]spiperone radioreceptor assay. Kinetic studies revealed that maximum binding of [3H]spiperone in hippocampus was much smaller than in striatum and frontal cortex but much higher than in cerebellum. In inhibition studies of [3H]spiperone binding, all neuroleptics tested were active in hippocampus as well as in striatum. In contrast, 5HT antagonists were definitely less potent in these two brain regions than in frontal cortex. Finally, even when 5HT receptors were blocked, dipropyl-ATN and haloperidol remained fully effective in hippocampus, striatum, but also in frontal cortex although to a lesser degree. From these results it was concluded that [3H]spiperone binds mainly to DA receptors in hippocampus as well as in striatum, whereas both 5HT and DA receptors are present in frontal cortex.

Animals↗
PubMed1985

In vivo stereospecific [3H]spiperone binding in rat brain: characteristics, regional distribution, kinetics and pharmacological properties.

The time course of [3H]spiperone distribution in the three major pools (specifically and non-specifically membrane-bound and soluble) of different brain areas, was studied in rats given a tracer amount of the drug. In addition, the stereospecificity, dissociation kinetics and pharmacological nature of the in vivo bound [3H]spiperone were investigated. The data show that [3H]spiperone binding sites in the striatum, olfactory tubercles and hypophysis differ clearly from those of the cortical regions. In the prevalently dopaminergic areas the amount of ligand bound to membranes is, up to 24 h post-treatment, proportional to the total 3H present. However a more correct analysis of the data was obtained in all the experiments when membrane-bound was measured instead of total radioactivity. Thus assay of the in vivo specifically bound [3H]spiperone appears essential for a correct evaluation of the density, affinity, regional distribution, pharmacological nature and kinetics of the drug-receptor interaction.

Animals↗
PubMed1985

Chronic proglumide increases [3H]spiperone binding in the rat brain.

The cholecystokinin (CCK) antagonist, proglumide, administered chronically (41.0-53.5 mg/kg per day, 14 days) to rats via osmotic mini-pumps, produced a significant 13% increase in the number of [3H]spiperone labeled binding sites (Bmax) in the striatum. There was no associated change in the affinity (Kd) of [3H]spiperone for the striatal binding sites. Given chronically at lower dose levels (10.4-13.6 or 21.8-29.8 mg/kg per day), or acutely in doses of 10, 20 or 40 mg/kg s.c., proglumide failed to alter the binding of [3H]spiperone to rat striatal tissue. These data indicate long-term proglumide administration increases the number of binding sites for [3H]spiperone, thought to be a ligand for dopamine D-2 receptors.

Animals↗
PubMed1988

Electrophysiological evidence that spiperone is an antagonist of 5-HT1A receptors in the dorsal raphe nucleus.

The neuroleptic spiperone, which binds to 5-HT1A, 5-HT2 and dopamine (DA) receptors, was studied for its effects on serotonin (5-HT) and DA neurons in dorsal raphe nucleus and substantia nigra pars compacta, respectively. We found that 1 mg/kg i.v. spiperone, but not LY53837 (a 5-HT2 antagonist), antagonized the inhibition induced by 5-HT1A agonists 8-hydroxy-dipropylaminotetralin (8-OH-DPAT) and buspirone in the dorsal raphe nucleus. Lower spiperone doses blocked DA receptors in substantia nigra pars compacta, but did not affect 5-HT neurons. Doses of 8-OH-DPAT completely silencing dorsal raphe neurons were ineffective in substantia nigra pars compacta. However, buspirone antagonized DA receptors in substantia nigra pars compacta with doses similar to those depressing dorsal raphe neurons. It is concluded that spiperone is an antagonist of 5-HT1A receptors in the dorsal raphe nucleus.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1989

Comparison of [3H]YM-09151-2 with [3H]spiperone and [3H]raclopride for dopamine d-2 receptor binding to rat striatum.

The Kd value of [3H]YM-09151-2, a potent and highly selective dopamine D-2 antagonist, for binding to rat striatum was about 20 pM (half of that for [3H]spiperone and one-fiftieth of that for [3H]raclopride). The Bmax of [3H]YM-09151-2 binding was about 30% higher than that of [3H]raclopride or [3]spiperone. The ratio (bout 3%) of non-specific to specific binding of [3H]YM-09151-2 was smaller than that of [3H]spiperone and [3H]raclopride. The Hill coefficient values of dopamine D-2 antagonists, SCH23390, mianserin and phentolamine for the inhibition of binding of [3H]YM-09151-2 were near 1.0, and their Ki values with [3H]YM-09151-2 were consistent with those for inhibiting [3H]raclopride and [3H]spiperone binding to D-2 receptors. Thus, [3H]YM-09151-2 may be the most suitable ligand for the labelling of dopamine D-2 receptors in the brain.

Animals↗
PubMed1996

Critical reevaluation of spiperone and benzamide binding to dopamine D2 receptors: evidence for identical binding sites.

There are several inconsistencies in the literature as regards the characteristics of benzamide and butyrophenone binding to dopamine D2-like receptors. The variations observed in Bmax, Kd and Ki values have led to hypotheses, such as the existence of a specific "benzamide binding site' and that dopamine D2 receptors exist in a monomer-dimer equilibrium, where benzamides are supposed to bind receptor monomers and butyrophenones receptor dimers. We have previously suggested that the discrepant results may instead be related to methodological difficulties associated with the use of very high-affinity radioligands (e.g. ligand depletion and failure to achieve equilibrium). The present study was designed to reinvestigate and critically reevaluate the binding characteristics of [3H]spiperone, [3H]nemonapride, [125I](S)-3-iodo-N-[(1-ethyl-2-pyrrolidinyl)methyl]-5,6- dimethylsalicylamide ([125I]NCQ-298) and [3H]raclopride to cloned human dopamine D2A and rat striatal dopamine D2 receptors in order to establish whether they label the same receptor population. We found that the Kd values of [3H]spiperone, [125I]NCQ-298 and [3H]nemonapride were about 20 pM and that of [3H]raclopride about 1 nM. We did not find any significant differences between the Bmax values determined with the various radioligands. Furthermore, the Ki values of spiperone and NCQ-298 (derived from cross-competition studies) for dopamine D2 receptors labelled with either [3H]spiperone or [125I]NCQ-298 were in good agreement with the corresponding Kd values. In conclusion, our results clearly demonstrate that when studied under correct experimental conditions, all four radioligands label an identical receptor population.

Animals↗
PubMed1989

In vitro binding characteristics of [3H]spiperone to the pituitary of the goldfish (Carassius auratus).

Homogenates of the pituitary of the goldfish (Carassius auratus) were incubated with [3H]spiperone under various experimental paradigms to evaluate the binding characteristics of the goldfish pituitary dopamine receptor. Binding was tissue specific as binding of [3H]spiperone to goldfish pituitary was greater than other tissue types examined, and the magnitude of binding was found to be dependent on pituitary (protein) content; also, specific binding was heat labile. Association was rapid and binding was reversible (dissociable) by addition of excess competing ligand (domperidone, a specific dopamine D2 receptor antagonist); the half-life (t1/2) of dissociation was 9.2 min and the estimated dissociation rate constant (k-1) was 7.56 x 10(-2) min-1); as well, the association rate was temperature dependent. Binding was saturable; saturation analysis using [3H]spiperone indicated a single class of binding sites with an estimated dissociation constant (Kd) and capacity of 7.39 +/- 1.23 x 10(-6) M and 31.56 +/- 2.72 x 10(-9) mol/mg protein, respectively. [3H]Spiperone binding was displaceable; displacement analysis using unlabeled domperidone indicated a single class of binding sites with estimated Kd and capacity of 2.94 +/- 0.54 x 10(-6) M and 19.47 +/- 3.12 x 10(-9) mol/mg protein, respectively. Binding was specifically inhibited by various dopamine antagonists and agonists. The density of binding sites differed significantly between regions of the goldfish pituitary; the number of binding sites in the pars distalis and neurointermediate lobes was estimated as 38.89 +/- 2.07 x 10(-9) mol/mg protein vs 109.45 +/- 25.33 x 10(-9) mol/mg protein, respectively; while the Kd's estimated as 3.73 +/- 0.248 x 10(-6) M vs 4.1 +/- 1.21 x 10(-6) M, respectively, were not significantly different. These data agree with previous in vivo and in vitro findings of the biological actions of dopamine agonists and antagonists in modifying gonadotropic hormone release in the goldfish and represent the first demonstration of the existence and binding characteristics of a dopamine/neuroleptic receptor in the pituitary of a nonmammalian vertebrate.

Animals↗
PubMed1979

Regional displacement by sulpiride of [3H]spiperone binding in vivo. Biochemical and behavioural evidence for a preferential action of limbic and nigral dopamine receptors.

The regional displacement by sulpiride of [3H]spiperone binding in vivo was studied in the rat. A low dose of sulpiride (20 mg/kg) displaced [3H]spiperone binding in certain limbic regions (olfactory tubercle, septum) and the substantia nigra but not in the nucleus accumbens or striatum. At this does sulpiride preferentially blocked apomorphine induced apomorphine Higher doses of sulpiride (150 and 250 mg/kg), which blocked apomorphine induced stereotypes and induced catalepsy were found to displace [3H]spiperone binding in all regions studied including the striatum and the nucleus accumbens. Haloperidol (0.1 and 1.0 mg/kg) displaced [3H]spiperone to approximately the same extent in all regions studied.

Animals↗
PubMed1982

Localization of [3H]spiperone binding sites in the intermediate lobe of the rat pituitary gland.

[3H]Spiperone binding sites in all three lobes of the rat pituitary gland were studied using an in vitro autoradiographic technique. [3H]Spiperone binding was present throughout the pituitary gland but there was a much higher density of autoradiographic silver grains over the cells of the intermediate lobe than elsewhere. The density of spiperone binding sites in pars intermedia was comparable to that in sections of the rat corpus striatum. [3H]Spiperone binding was displaced by the specific dopamine agonist ADTN.

Animals↗
PubMed1995

Differential effects of [3H]nemonapride and [3H]spiperone binding on human dopamine D4 receptors.

We compared some binding parameters of [3H]nemonapride and [3H]spiperone in human dopamine D4 (hD4) receptors with three different numbers of tandem repeat units. Although both of the radioligands showed similar affinity constants for each hD4 receptor variant, the maximal number of binding sites labeled by [3H]nemonapride was approximately 1.35-fold higher than that by [3H]-spiperone for all variants. Estimated Ki values for the inhibition of [3H]nemonapride binding by a series of dopaminergic ligands were highly correlated to respective values obtained for the inhibition of [3H]spiperone binding to each hD4 receptor. These results suggest that the hD4 receptor, as shown for the D2 receptor, may exist in multiple molecular forms as a monomer-dimer equilibria, and that [3H]spiperone may discriminate in the multiple molecular forms.

Benzamides↗
PubMed1990

3-(2'-[18F]fluoroethyl)spiperone, a potent dopamine antagonist: synthesis, structural analysis and in-vivo utilization in humans.

The synthesis of 3-(2'-[18F]fluoroethyl)spiperone (1c), a radiotracer useful for imaging the brain dopamine receptor system in vivo using positron emission tomography, is described. Precursors of 1c, the functional 3-N-alkyl derivatives of spiperone (4), were prepared by the alkylation of the amide group in spiperone (2a) by 1,2-disubstituted ethanes under phase transfer conditions. A comprehensive evaluation of the reaction of the derivatives 4a-h with no-carrier-added K18F/Kryptofix clearly indicated that the ketalized derivatives 4e-h were the choice of the precursors for 1c. The i.r., MS and NMR spectral data suggested that under phase transfer reaction conditions, the amide nitrogen was preferentially alkylated. To provide a firm basis for comparison with related analogues, an x-ray analysis was performed on a single crystal of 3-(2'-fluoroethyl)spiperone (1d). The tomographic behavior of 1c in human brain tissue was measured for more than 7 h and was consistent with the labeling of dopamine D-2 receptors.

Brain↗
PubMed1986

No-carrier-added 3-(2'-[18F]fluoroethyl)spiperone, a new dopamine receptor-binding tracer for positron emission tomography.

No-carrier-added (NCA)3-(2'-[18F]fluoroethyl)spiperone (5), a new dopamine receptor-binding radiopharmaceutical for positron emission tomography, was synthesized by two different methods. Alkylation of the amide nitrogen in spiperone by NCA [18F]fluorobromoethane in the presence of a strong base gave 5 (Method A). Experimental methods were also developed for the syntheses of functional 3-N-alkylderivatives of spiperone such as 3-(2'-bromoethyl)- or 3-(2'-methylsulfonyloxyethyl)spiperone (4a and 4b, respectively). These derivatives (4) reacted with NCA Ag18F, Cs18F or K18F/Kryptofix 222 in acetonitrile or DMSO to give 5 (Method B). Method B, using K18F/Kryptofix 222 in acetonitrile provided 5 in multimillicure amounts (30-40% isolated radiochemical yield) with a specific activity of 2-10/mumol (EOS) in less than 60 min. This one-step, one-pot synthesis is simple, and the high radiochemical yield of 5, as well as the 110 min half-life of 18F, permit multiple tomographic studies a day with one preparation. Tomographic results in monkey brain with 5 are consistent with the labeling of dopamine-D2 receptor systems.

Animals↗
PubMed2002

Decreased [(3)H]spiperone binding in the anterior cingulate cortex of schizophrenia patients: an autoradiographic study.

Abnormalities in the anterior cingulate cortex have been reported in patients with schizophrenia, and have been implicated in the pathophysiology of this disorder. In the present study, we have examined antipsychotic-sensitive binding sites in the left anterior cingulate cortex of schizophrenia patients and controls. Using quantitative autoradiography and [(3)H]spiperone as a ligand, both saturation and competition experiments were performed in post-mortem brain tissue obtained from six schizophrenia and six control cases. Saturation experiments revealed that the maximum number of [(3)H]spiperone binding sites was significantly reduced by 31% in the schizophrenia group as compared to the control group (65.3+/-5.6 fmol/mg tissue versus 94.2+/-7.3 fmol/mg tissue). Increased dissociation constant was also observed in the schizophrenia group (2.2+/-0.4 nM versus 1.3+/-0.2 nM), but was not statistically significant (P=0.07). Competition experiments were performed in order to examine the pharmacological profile of [(3)H]spiperone binding, and revealed that: (i) displacement of [(3)H]spiperone binding by clozapine and mianserin was significantly reduced in the schizophrenia group as compared to the control group (-26% and -16% respectively); (ii) the order of displacement potency of the drugs tested was: haloperidol>mianserin>butaclamol approximately risperidone>clozapine>2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene. Our results suggest a reduction of antipsychotic-sensitive binding sites in the anterior cingulate cortex of patients with schizophrenia. Such abnormality could lead to an imbalance in neurotransmitter regulation in the anterior cingulate cortex which may contribute to the emergence of some symptoms of schizophrenia.

Adult↗
PubMed1992

Effect of N-alkylation on the affinities of analogues of spiperone for dopamine D2 and serotonin 5-HT2 receptors.

Two series of N-substituted spiperone analogues were prepared and evaluated in vitro to measure their affinities for dopamine D2 and serotonin 5-HT2 receptors. Substitution of the amide nitrogen with an alkyl group of five carbon units or less resulted in analogues displaying a low selectivity for D2 compared to 5-HT2 receptors. However, a moderate improvement in selectivity for D2 receptors was observed with N-benzylspiperone. Substitution at either the ortho or para position of the benzyl group resulted in a further reduction in affinity for 5-HT2 receptors and improvement in the selectivity ratio. Examination of N-substituted analogues of spiperone may provide insights into the topography of the antagonist binding region of the 5-HT2 receptor. The results also suggest that an 18F-labeled analogue of N-(4-nitrobenzyl)spiperone (4p) may be a suitable tracer for studying D2 receptors with positron emission tomography since this compound displays a high selectivity for D2 receptors relative to that of spiperone and N-methylspiperone.

Alkylation↗
PubMed1998

Spiperone: influence of spiro ring substituents on 5-HT2A serotonin receptor binding.

Spiperone (1) is a widely used pharmacological tool that acts as a potent dopamine D2, serotonin 5-HT1A, and serotonin 5-HT2A antagonist. Although spiperone also binds at 5-HT2C receptors, it is one of the very few agents that display some (ca. 1000-fold) binding selectivity for 5-HT2A versus 5-HT2C receptors and, hence, might serve as a useful template for the development of novel 5-HT2A antagonists if the impact of its various substituent groups on binding was known. In the present investigation we focused on the 1, 3,8-triazaspiro[4.5]decanone portion of spiperone and found that replacement of the N1-phenyl group with a methyl group only slightly decreased affinity for cloned rat 5-HT2A receptors. However, N1-methyl derivatives displayed significantly reduced affinity for 5-HT1A, 5-HT2C, and dopamine D2 receptors. Several representative examples were shown to behave as 5-HT2 antagonists. As such, N1-alkyl analogues of spiperone may afford entry into a novel series of 5-HT2A-selective antagonists.

3T3 Cells↗
PubMed1990

In vitro pharmacological profile of 3-N-(2-fluoroethyl)spiperone.

The binding affinities of spiperone and 3-N-(2-fluoroethyl)spiperone (FESP) have been compared for several rodent brain receptor sites and for inhibition of monoamine release and uptake sites. FESP and spiperone have almost identical profiles, namely a high affinity for dopamine-D2 and serotonin-S2 receptors, a low affinity for alpha 1-adrenergic receptors, and negligible binding to other sites. These results suggest that available data on spiperone binding may be applied to the interpretation of PET data obtained with FESP.

Animals↗
PubMed1990

In vivo binding of spiperone and N-methylspiperone to dopaminergic and serotonergic sites in the rat brain: multiple modeling and implications for PET scanning.

Equilibrium models are derived and applied to in vivo binding of spiperone in the rat brain. The models express the concentration of the ligand in the striatum and frontal cortex as a function of the accumulation in the cerebellum. The models differ with respect to the description of specific binding. Nonlinear regression analysis shows that the in vivo specific binding of 3H-labeled spiperone in the frontal cortex (mainly serotonergic) can be described by a noninteracting sites model, whereas the specific binding in the striatum (mainly dopaminergic) can best be described by models that lead to sigmoid saturation curves. These results were tested and partly confirmed by determining the region-of-interest/cerebellar radioactivity ratio of 11C-labeled N-methylspiperone, with and without pretreatment with haloperidol. The estimated Bmax was 32 fmol/mg wet tissue in the frontal cortex and approximately 90 fmol/mg wet tissue in the striatum. The free plus nonspecific binding of spiperone was similar in the frontal cortex but lower in the striatum than in the cerebellum. The occurrence of sigmoidicity can be best explained by the existence of high-affinity/low-capacity sites in the cerebellum rather than mutual interactions of striatal sites. The consequence of the present analysis for positron emission tomography is that the striatal/cerebellar activity ratio is not an accurate parameter of specific binding features at tracer doses of spiperone or N-methylspiperone.

Animals↗