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2-thioxanthone thioacetic acid (TXSCH 2 COOH, T), which has a fluorometric character, was used for new fluorometric system upon Fe(II) analysis in biological samples as the main target. T-BSA binary complex was firstly consisted with non-covalent interactions between T and BSA at the equilibrium concentration as 1.77 × 10 -4. M. T-BSA binary complex emission was increased at the ratio of 24.40% due to stabilization property of BSA (pH:7), compared with T emission intensity. Fluorescence emission spectroscopy was used for the all measurements because of an economic, a sensitive and a practical method compared with other spectroscopic analysis. T-BSA-Fe(II) triple complex was also obtained by adding Fe(II) ion to T-BSA binary complex solution. Its characterization was performed to be investigated with optimum excitation wavelength, buffer concentration, pH and temperature as 297 nm, 10 -3 M Tris HCl (10 -2 M NaCI), pH:7.2 at 25 °C, respectively. The results of Fe(II) analysis in serum showed a certain response in fluorometric T-BSA-Fe(II) triple complex measurement system as 50.42 ± 5.8 µg/dL. The analyses of our fluorometric triple complex system were compared with the reference electrochemiluminescence method and similar results were obtained. Fluorometric measurements of T-BSA-Fe(II) triple complex, its characterization and Fe(II) analysis in this system have not been investigated in literature gives originality to our study.

Thioxanthone and its derivatives are the most remarkable molecules due to their vast variety of application such as radiation curing that is, until using them as a therapeutic drug. Therefore, in this study it was intended to use 2-Thioxanthone acetic acid with and without NaCl in Tris HCl buffer solution (pH:7.0) to represent the interaction with ct-DNA. The UV-vis absorption spectra of TXCH 2 COOH in the presence of ct-DNA showed hypochromism and the intrinstic binding constant (K b ) was determined as 6 × 10 3  L mol -1 . The fluoresence intensity of TXCH 2 COOH with ct-DNA clearly increased up to 101% which indicated that the fluorescence intensity was very sensitive to ct-DNA concentration. The binding constant (K) and the values of number of binding sites (n) and were calculated as 1.8 × 10 3  L mol -1 and 0.69, respectively. When the quenching constants (K sv ) of free TXCH 2 COOH and TXCH 2 COOH, which were bonded with ct-DNA were compared, slightly changed values of Ksv were seen. Moreover, displacement assay with Hoechst 33,258 and viscosity measurements in the presence and absence of NaCl salt also confirmed the binding mode which noted the electrostatic interaction following groove binding between TXCH 2 COOH and ct-DNA. Last but not least, the salt effect was examined on ct-DNA binding with TXCH 2 COOH. The results of the experiments indicated that the groove binding was strengthened by NaCl whereas in the high NaCl concentration, the binding ability of TXCH 2 COOH to ct-DNA was inversely affected., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Serotonin 5-HT2B receptor antagonists have been proposed as migraine prophylactic drugs, but previously available 5-HT2B receptor antagonists displayed multiple monoaminergic side effects and had to be withdrawn from the market. Here, we set out to identify a novel antagonist with high affinity and selectivity towards 5-HT2B receptors. To test the affinity of new compounds towards various receptors, we generated a broad series of cells functionally coupling human monoaminergic receptors to luciferase. Using the cell lines we revealed pimethixene (1-methyl-4-(9H-thioxanthen-9-ylidene)piperidine) as highly potent, albeit non-selective 5-HT2B receptor antagonist and optimized its chemical structure to create highly potent and selective 5-HT2B receptor antagonists. We selected the methoxythioxanthene BF-1 for further analysis. In comparison to pimethixene, it lacked high affinities to 5-HT1A, 5-HT2A, 5-HT2C, histamine H1, dopamine D1 and D2 as well as muscarinic M1 and M2 receptors. BF-1 was tested as potential migraine prophylactic drug by blocking meta-chlorophenylpiperazine, (mCPP) or BW723C86 (5-((thiophen-2-yl)methoxy)-α-methyltryptamine) induced neurogenic dural plasma protein extravasation in a guinea pig model that may resemble a migraine attack. BF-1 was significantly more potent in this assay compared to the well know non-selective 5-HT2B antagonists, methysergide ((6aR,9R)-N-[(2S)-1-Hydroxybutan-2-yl]-4,7-dimethyl-6,6a,8,9-tetrahydroindolo[4,3-fg]quinoline-9-carboxamide) or pizotifen (4-(1-methyl-4-piperidylidine)-9,10-dihydro-4H-benzo-[4,5]cyclohepta[1,2]-thiophene). Therefore, we propose BF-1 as a new compound that may be developed for prophylactic migraine treatment without the typical monoaminergic side effects., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Foodstuff could be a vector for naturally occurring and/or unwanted dangerous substances that can act either as they are or after their bioactivation. The scientific community agrees that the metabolic activity of chemicals should be taken into account for proper risk assessment. Unfortunately, the in vitro evaluation of a metabolic panel and analytical/biochemical detection in food-safety assessment are very expensive and challenging because of the abundance of data to analyze. In this context, properly validated computational protocols could be a useful tool for making metabolic and binding/activity predictions. This strategy has been applied to thioxanthone photoinitiators (TX), identified as food contaminants, especially in infant formulas, as reported by the European Food Safety Authority in 2005. Their lipophilicity suggests rapid hepatic metabolism, but the currently available data only concern 2-ITX. We have predicted phase I metabolites for the TX class of compounds and defined their binding affinity for the AR ligand-binding pocket using a local model based on available information about metabolism and AR activity. Some metabolites should undergo further in vitro or/and in vivo toxicological evaluations because they have proved to be suitable as ligands for AR.

In recent years, various biological processes have been found to be regulated by miRNA-mediated gene silencing. A small molecule that modulate the miRNA pathway will provide the biological tool for elucidating mechanisms of miRNA-mediated gene regulation, and can be the drug lead for miRNA related diseases. In this study, we demonstrated that an aminoalkoxy-substituted thioxanthone derivative interferes Dicer-mediated processing of pre-miRNA. Information about the interaction between these xanthone derivatives and pre-miRNAs will enable us to design and develop new small molecule-based inhibitors for miRNA pathway., (Copyright © 2012. Published by Elsevier Ltd.)

Rationale: Inflammation and oxidative stress are linked to the deleterious effects of cigarette smoke in producing chronic obstructive pulmonary disease (COPD). Myeloperoxidase (MPO), a neutrophil and macrophage product, is important in bacterial killing, but also drives inflammatory reactions and tissue oxidation., Objectives: To determine the role of MPO in COPD., Methods: We treated guinea pigs with a 2-thioxanthine MPO inhibitor, AZ1, in a 6-month cigarette smoke exposure model, with one group receiving compound from Smoking Day 1 and another group treated after 3 months of smoke exposure., Results: At 6 months both treatments abolished smoke-induced increases in lavage inflammatory cells, largely ameliorated physiological changes, and prevented or stopped progression of morphologic emphysema and small airway remodeling. Cigarette smoke caused a marked increase in immunohistochemical staining for the myeloperoxidase-generated protein oxidation marker dityrosine, and this effect was considerably decreased with both treatment arms. Serum 8-isoprostane, another marker of oxidative stress, showed similar trends. Both treatments also prevented muscularization of the small intrapulmonary arteries, but only partially ameliorated smoke-induced pulmonary hypertension. Acutely, AZ1 prevented smoke-induced increases in expression of cytokine mediators and nuclear factor-κB binding., Conclusions: We conclude that an MPO inhibitor is able to stop progression of emphysema and small airway remodeling and to partially protect against pulmonary hypertension, even when treatment starts relatively late in the course of long-term smoke exposure, suggesting that inhibition of MPO may be a novel and useful therapeutic treatment for COPD. Protection appears to relate to inhibition of oxidative damage and down-regulation of the smoke-induced inflammatory response.

1. 2-Isopropyl-9H-thioxanthen-9-one (2-ITX) is one of the most extensively used photoinitiators in inks found in paper and/or packaging materials for foodstuffs. Recently, traces of 2-ITX as a contaminant were discovered in baby milk and other foodstuffs at a level sufficient to pose a risk to human health. However, little is known about the toxicological profile of 2-ITX. 2. The high lipophilicity of this substance would suggest that it could be a good substrate for hepatic metabolizing enzymes and that these metabolites could have a role in the toxicological properties of 2-ITX. 3. The metabolism of 2-ITX, using both rat and human subcellular preparations, was studied and has resulted in the formation of eight polar metabolites (M1-M8) as revealed in the liquid chromatograpy/ultraviolet (LC/UV) and liquid chromatograpy/mass spectrometry (LC/MS) analyses. Their structures highlight a marked regioselectivity in the metabolism of 2-ITX; it is directed mainly toward the isopropyl moiety and the sulfur atom. 4. The unsaturated metabolite 6 causes the formation of a reactive epoxide metabolite 7. This finding was supported by identification in microsomal incubations of 1,2-diol metabolite 8 arising from the epoxide by hydrolysis and it was validated by incubating in the same conditions the synthetic epoxide 7: the formation of metabolite 8 was again observed. 5. On the basis of these data, we propose that the metabolite 6 could be included in toxicological studies of 2-ITX.

Xanthine oxidase-catalyzed hydroxylation reactions of the anticancer drug 6-mercaptopurine (6-MP) and its analog 2-mercaptopurine (2-MP) as well as 6-thioxanthine (6-TX) and 2-thioxanthine (2-TX) have been studied using UV-spectroscopy, high pressure liquid chromatography, photodiode array, and liquid chromatography-based mass spectral analysis. It is shown that 6-MP and 2-MP are oxidatively hydroxylated through different pathways. Enzymatic hydroxylation of 6-MP forms 6-thiouric acid in two steps involving 6-TX as the intermediate, whereas 2-MP is converted to 8-hydroxy-2-mercaptopurine as the expected end product in one step. Surprisingly, in contrast to the other thiopurines, enzymatic hydroxylation of 2-MP showed a unique hyperchromic effect at 264 nm as the reaction proceeded. However, when 2-TX is used as the substrate, it is hydroxylated to 2-thiouric acid. The enzymatic hydroxylation of 2-MP is considerably faster than that of 6-MP, while 6-TX and 2-TX show similar rates under identical reaction conditions. The reason why 2-MP is a better substrate than 6-MP and how the chemical nature and position of the functional groups present on the thiopurine substrates influence xanthine oxidase activity are discussed.

An investigation of the structure-affinity relationships for the binding of thioxanthene-related structures indicates that an intact thioxanthene ring is not required for binding at sigma(1) receptors, and that with the appropriate structural modifications, affinity can be enhanced to the subnanomolar level. Certain of the analogs displayed sigma(1)-fold selectivity for sigma(1) versus sigma(2) receptors.

The potential for drug-drug interactions in psychiatry and patients with epilepsy is very high. Moreover, antiepileptic drugs are widely used outside epilepsy as psychotropic agents and their spectrum of activity on behavior is of considerable interest to psychopharmacology. In both neurologic and psychiatric practice, pharmacotherapy combinations are commonly used to treat comorbid psychiatric and neurologic disorders, to reduce or control the adverse effects of a medication or to increase its efficacy. This paper focuses on the metabolic pharmacokinetic interactions between two classes of psychotropic drugs: antiepileptic and antipsychotic drugs. The degree of documentation varies for many interactions from clinical case-report experiences to well established research outcomes. The evidence and the clinical significance of these interactions are reviewed. In general, it is better to use as few drugs as possible, as multicolored politherapies increase the possible adverse effects of drug interactions and reduce patient compliance.

Dopamine receptors were studied in post-mortem brains from control and Huntington's disease patients, using the specific binding of [3H]spiperone to dopamine D-2 receptors and [3H]piflutixol to dopamine D-1 receptors. Both [3H]spiperone binding and [3H]piflutixol binding were reduced by 45-50% in Huntington's disease putamen. The loss of [3H]spiperone and [3H]piflutixol binding sites correlated with decreased GABA concentrations observed in Huntington's disease putamen. A selective loss (48%) of [3H]piflutixol binding was observed in Huntington's disease substantia nigra pars reticulata, [3H]piflutixol binding was unchanged in substantia nigra pars compacta. No differences in [3H]spiperone binding were observed between the groups in either region of substantia nigra. The results are discussed in relation to the pathophysiology of Huntington's disease, and to the presence of distinct dopamine receptors in human brain.

The release from the depot, hydrolysis and distribution in the organsim as well as the metabolism and elimination of intramuscularly injected clopenthixol decanoate in Viscoleo have been studied in dogs and rats with radioactive as well as non-labelled drug after single as well as repeated administration. The studies clearly demonstrate the depot effect of clopenthixol decanoate given intramuscularly in oil compared to orally administered clopenthixol. The amounts of drug remaining at the site of injection in dogs suggest monoexponential release of drug from the depot and a half-life of 4-5 days. Rapid hydrolysis to clopenthixol in the organism was indicated by in vitro experiments and in vivo findings. Clopenthixol was found to be the main compound in the organism after single as well as repeated doses. The clopenthixol formed by hydrolysis appeared to be metabolized in the same way as clopenthixol given orally i.e. by dealkylation of the side chain and by S-oxide and N-oxide formation. The elimination pattern with predominant fecal excretion also appeared to be the same after clopenthixol and its esterified derivative apart from the reflection in the latter case of the slow release from depot. A rapid exchange in the organism between tritium from the drugs and hydrogen from the body water was demonstrated. This has to be considered in studies with tritium labelled drugs, where estimation of total radioactivity gives the sum of tritium in drug, metabolites and water.

In dopamine (DA) receptor binding tests two different receptor populations can be measured. By using 3H-haloperidol or 3H-spiroperidol as ligands D-2 receptors are detected. When the thioxanthene neuroleptics 3H-cis (Z)-flupenthixol or 3H-piflutixol are used as ligands D-1 receptors coupled to adenylate cyclase can be detected. In displacement experiments butyrophenones (haloperidol and spiroperidol) and diphenylbutylpiperidines (pimozide) interact with D-2 receptors only, whereas thioxanthenes (cis [Z]-flupenthixol, cis [Z]-piflutixol and cis [Z]-clopenthixol) have equal affinity for D-1 and D-2 receptors. A similar differentiation is also seen in behavioral studies. The methylphenidate antagonistic effect of butyrophenones and diphenylbutylpiperidines is dramatically attenuated by concomitant treatment with an anticholinergic agent or a GABA agonist. The effect of thioxanthenes is almost unchanged. When mice are treated for 12 days with neuroleptics, supersensitivity to methylphenidate is induced. The supersensitivity is reversed by thioxanthenes, whereas butyrophenones and diphenylbutylpiperidines have no effect at all. These differences do not appear to be due to a change in the affinity for DA receptors because the ability of cis (Z)-flupenthixol, haloperidol, DA or apomorphine to displace 3H-piflutixol or 3H-spiroperidol is the same in supersensitive and control mice. The results clearly demonstrate that neuroleptics acting on both D-1 and D-2 receptors have a behavioral profile different from that of neuroleptics acting exclusively on D-2 receptors.

The rate of excretion of labelled hycanthone has been determined in bile and urine from three strains of rats (Sprague-Dawley, hooded and Gunn), and from dogs, cats, rabbits and monkeys. Bile was the major route of excretion in all species; the half-life for excretion of total radioactivity ranged from 1.6 to 3.0 hours. Relatively little of the radioactivity was found in the urine, except in the monkey and notably in the cat. Most of the radioactivity in the bile and urine was found in conjugated form, or as polar metabolites; cat urine, however contained a high percentage of hycanthone and less polar metabolites. Some fifteen metabolites have been seen in bile, and/or urine, and nine from in vitro incubations with microsomal preparations. Five of these, including hycanthone, have been chemically characterized, and two others tentatively identified.

Chronic treatment of rats with the MAOI clorgyline significantly reduced the density (Bmax) of cortical beta-adrenergic receptors but did not alter either the Bmax or dissociation constant (Kd) of 3H-spiperone binding to striatal DA receptors. Clorgyline co-treatment also did not significantly affect either behavioral supersensitivity to apomorphine or the increase in 3H-spiperone binding induced by chronic haloperidol. In contrast, repeated treatment with the DA uptake inhibitor amfonelic acid elicited behavioral subsensitivity and reduced striatal 3H-spiperone binding. Furthermore, amfonelic acid co-treatment prevented haloperidol-induced behavioral and receptor binding changes. The possible relevance of these findings in relation to drug choice in clinical trials of receptor sensitivity modification are discussed.

Characteristics of membrane receptor binding by 3H-cis-flupenthixol were examined in rat striatum. Using modifications of standard dopamine receptor binding techniques, it was possible to obtain 70% specific binding with 3H-cis-flupenthixol. Association and dissociation rates were very rapid, with equilibrium reached in 2 min and half-time of dissociation being 1 min. Analysis of saturation and competition studies using cis-flupenthixol and spiroperidol indicated that cis-flupenthixol binds to two striatal receptors with apparent KD's of 0.7 and 4.8 nM. It is suggested these represent D1 and D2 dopamine receptors respectively. The further characterization of the properties of cis-flupenthixol binding presented here should enable more detailed studies of multiple dopamine receptors to be designed.

The binding of 3H-cis flupenthixol (3H-FPT) to calf brain membranes was investigated in vitro. Highest levels of 3H-FPT binding were observed in striatum and nucleus accumbens, whilst no significant binding was observed in pituitary. The potencies of neuroleptics, dopaminergic ergot alkaloids and dopamine (DA) agonists in inhibiting 3H-FPT binding to calf striatal membranes were compared with their potencies in inhibiting 3H-spiperone (3H-SPIP) binding and DA-stimulated adenylate cyclase (AC). A high correlation was observed between drug potencies in inhibiting 3H-FPT binding and DA stimulated AC. However, potencies of the drugs inhibiting 3H-SPIP binding were only weakly correlated with their potencies in inhibiting either 3H-FPT binding or DA stimulated AC. A detailed analysis of the inhibition of 3H-FPT binding by butyrophenones revealed two classes of 3H-FPT binding sites. It is suggested that 3H-FPT binds predominantly to a class of dopaminergic sites associated with DA-stimulated AC.

Cis(Z)-clopenthixol decanoate in Viscoleo (Sordinol Depot, Cisordinol Depot, Clopixol Inj.) was given intramuscularly to nine schizophrenic patients with dosage intervals of 1 or 2 weeks. Serum concentrations of the two geometric isomers of clopenthixol and its N-dealkyl metabolite were recorded in two successive dosage intervals. Significant correlations were found for dose vs area under the serum concentration curve and vs serum concentrations measured on individual days. The last mentioned concentrations are good measures of the area under the serum concentration curve, which expresses the drug load of the patient. The serum concentration curves in two successive dosage intervals were very similar. Maximum serum concentration was seen 5-7 days after injection and the mean maximum/minimum fluctuation was 1.6 with the 2-week dosage interval. The finding of very low amounts of the trans(E)-isomers of clopenthixol and the N-dealkyl-metabolite shows that isomerization of the cis(Z)-compounds into the corresponding trans(E)-isomers does not take place within the organism.

Dopamine receptors in human parathyroid were studied in vitro using ligand binding techniques. With 3H-piflutixol as ligand, binding characteristic of the dopamine D1 receptor was observed. Administration of apomorphine, flupenthixol or metoclopramide to normal controls or acute schizophrenic patients at doses producing significant alterations in serum prolactin concentrations did not alter serum parathyroid hormone (PTH) concentrations. Whilst D1 binding sites are present in human parathyroid, the measurement of PTH after administration of dopaminergic drugs is unlikely to provide a test of D1 receptor function in man.

Hycanthone is a drug used for the clinical treatment of schistosomiasis, although inducing chromosomes breaks and mutagenesis when it enters the DNA double helix. Based on visual observation of characteristics of basophilia and anisotropy after toluidine blue staining, a preferential binding of hycanthone to heterochromatin could be demonstrated for the nuclei of the Malpighian tubules of Triatoma infestans. In other cellular systems like cattle kidney cells in culture, plant cells, and mouse lymphocytes, the drug could be demonstrated to bind heterochromatin and euchromatin, irrespective of the packing state of the latter. When penetrating the various heterochromatin types (with the exception of T. infestans), the drug induced a chromatin loosening that could favor incidence of chromatin breaks. The variation of hycanthone binding to DNA in different cell types is possibly related to differences in composition, stereo-arrangement and stability of the DNA-protein complexes involved.

A pharmacokinetic model incorporating 14 compartments and 29 transfer coefficients has been developed from experimental data obtained after intravenous administration of a single dose to describe the distribution of doxantrazole in the rate. The distribution calculated from the model agreed closely with that determined experimentally. In addition, the model was able to predict with considerable accuracy the distribution of doxantrazole after repeated dosing.

The interaction of beta-haloalkylamine derivatives of dopamine agonists and antagonists with 3H-spiperone binding (D2 sites) and 3H-flupenthixol binding (D1 sites) was studied. N-chloroethyl derivatives of phenothiazines and thioxanthenes were potent inhibitors of the binding of both ligands. The in vitro inhibition of binding produced by these compounds was irreversible. The drugs were however only weakly active in vivo. The results suggest that beta-haloalkylamine derivatives of neuroleptics may be useful compounds for studying dopamine receptors in vitro.

The binding characteristics of 3H-SCH 23390 in rat striatum prepared in potassium phosphate buffer are described. The amount of binding sites labeled by 3H-SCH 23390 decreased monoexponentially when exposed to increasing radiation dose. The molecular weight was determined to 78,000 daltons similar to the molecular mass of 3H-piflutixol binding to D-1 receptor previously reported, however lower than the molecular mass of dopamine D-1 agonist binding sites (Gredal & Nielsen 1987).

The development of dopamine D1 receptors in rat striatum during the early postnatal period is described, using [3H]piflutixol as ligand. Dopamine D1 receptors increase in number from day of birth until about 21 days of age, when they reach adult levels. This increase in number parallels the increase in several other dopamine markers in striatum during the same time period. The increase is reflected in an increase in Bmax of ligand binding to D1 receptors. All other properties of D1 receptors that were examined do not change throughout this developmental period and are essentially the same as those found in adult tissue. These include association and dissociation rates, affinity for piflutixol as determined by kinetic and saturation studies, and pharmacology. These studies provide a biochemical and pharmacological basis for further studies on the ontogeny of dopamine receptors and of striatum and on factors regulating development of this region.

Recovery of D1- and D2-dopamine receptors in Wistar rat corpora striata were assessed following N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ blockade). Absolute recovery declines during senescence approximately 25 and 40% for the D1- and D2-subtypes, respectively. Net biosynthetic reductions are comparable to the overall age-related decreases in receptor concentrations for this rat strain. EEDQ administration also induces catalepsy behavior and impairs ability of animals to remain on an inclined screen. Recovery of inclined screen performance is also reduced with age, but is not strictly proportional to recovery of receptor concentrations.

Genetic crosses between phenotypically resistant and sensitive schistosomes demonstrated that resistance to hycanthone and oxamniquine behaves like a recessive trait, thus suggesting that resistance is due to the lack of some factor. We hypothesized that, in order to kill schistosomes, hycanthone and oxamniquine need to be converted into an active metabolite by some parasite enzyme which, if inactive, results in drug resistance. Esterification of the drugs seemed to be the most likely event as it would lead to the production of an alkylating agent upon dissociation of the ester. An artificial ester of hycanthone was indeed active even in resistant worms, thus indirectly supporting our hypothesis. In addition, several lines of evidence demonstrated that exposure to hycanthone and oxamniquine results in alkylation of worm macromolecules. Thus, radioactive drugs formed covalent bonds with the DNA of sensitive (but not of resistant) schistosomes; an antiserum raised against hycanthone detected the presence of the drug in the purified DNA fraction of sensitive (but not of resistant) schistosomes; a drug-DNA adduct was isolated from hycanthone-treated worms and fully characterized as hycanthone-deoxyguanosine.

Comparison has been made of the effects on brain dopamine function of chronic administration of haloperidol or clozapine to rats for up to 12 months. In rats treated for 1-12 months with haloperidol (1.4-1.6 mg/kg/day), purposeless chewing jaw movements emerged. These movements were only observed after 12 months' treatment with clozapine (24-27 mg/kg/day). Apomorphine-induced (0.125-0.25 mg/kg) stereotyped behaviour was inhibited during 12 months treatment with haloperidol. Clozapine treatment was without effect. After 12 months, stereotypy induced by higher doses of apomorphine (0.5-1.0 mg/kg) was enhanced in haloperidol, but not clozapine, treated rats. Bmax for striatal 3H-spiperone binding was elevated throughout 12 months of haloperidol administration, but was not altered by clozapine treatment. Bmax for striatal 3H-NPA binding was only elevated after 12 months of haloperidol treatment; clozapine treatment was without effect. Bmax for 3H-piflutixol binding was not altered by haloperidol treatment, but was increased after 9 and 12 months of clozapine treatment. Dopamine (50 microM)-stimulated adenylate cyclase activity was inhibited after 1 month's haloperidol treatment but normal thereafter. Adenylate cyclase activity was not altered by chronic clozapine treatment. Striatal acetylcholine content was increased after 3 and 12 months of haloperidol or clozapine intake. These findings indicate that the chronic administration of the atypical neuroleptic clozapine does not produce changes in brain dopamine function which mirror those of the typical neuroleptic haloperidol. In particular, chronic administration of clozapine, unlike haloperidol, does not appear to induce striatal D-2 receptor supersensitivity. Unexpectedly, clozapine treatment, unlike haloperidol, altered D-1 receptor function.

The binding of 3H-cis flupenthixol (3H-FPT) to dopamine receptors in membrane preparations from control subjects and schizophrenics was studied. Using a fixed concentration of 3H-FPT, no differences were observed between controls and all schizophrenics, although 3H-FPT binding was increased in schizophrenics who apparently were drug-free at the time of death. Scatchard analysis of 3H-FPT binding revealed that in drug-treated schizophrenics both the number of binding sites (BM) and the dissociation constant (KD) were increased, whilst in drug-free schizophrenics only the BM was increased. Using domperidone to differentiate 3H-FPT binding to D1 and D2 dopamine sites, it was found that only D2 sites were increased in drug-free schizophrenics. The results are discussed with reference to previous studies on dopamine receptors in schizophrenia, and the effects of neuroleptic treatment. It is suggested that a selective increase in D2 receptors may be associated with the disease process in schizophrenia.

Certain polycyclic compounds with a coplanar ring structure (phenothiazines, thioxanthenes, 4-aminoquinolines, and amitriptyline), monocyclic sympathomimetic amines, and other drugs become concentrated in the eyes of animals following acute or chronic systemic administration. Some are known to cross the placental barrier and accumulate in the fetal eye. Following drug withdrawal, these substances disappear relatively slowly from ocular tissues compared with other tissues. The main reason for the accumulation of these compounds seem to be their affinity for the melanin of the uveal tract and pigment epithelium and they therefore do not accumulate in the eyes of albino animals. The mechanism of uptake by melanin probably involves a "charge transfer" reaction involving the transfer of an electron from drug to melanin, which acts as an "electron trap" and in consequence binds the donor compound firmly. The accumulation of a nontoxic drug in the eye is not necessarily of clinical significance, but ocular damage can occur in patients on long-term tricyclic agents when the amount, duration, and frequency of dosage are sufficiently high. The most serious form of ocular damage is pigmentary retinopathy, which, if caused by chloroquine, is irreversible. In contrast, phenothiazine retinopathy is reversible. Lesions may also be produced in anterior structures of the eye, usually the cornea and lens, by both chloroquine and the phenothiazines, but they are of a relatively minor nature. Possible mechanisms for the oculotoxicity of the phenothiazines and antimalarials are discussed, particularly in relation to melanin.

SCH 23390 potently displaced the specific binding of 3H-piflutixol to D-1 sites in striatal membranes but haloperidol was only weakly effective. SCH 23390 weakly displaced specific 3H-spiperone binding to D-2 sites, but haloperidol was potent. SCH 23390 was more effective than haloperidol in inhibiting dopamine stimulated striatal adenylate cyclase activity. These results confirm the D-1 selectivity of SCH 23390. However, SCH 23390 inhibited apomorphine-induced stereotypy and climbing behaviour in rats with equal potency to haloperidol. Haloperidol dose-dependently increased striatal HVA and DOPAC concentrations without altering dopamine content. Low doses of SCH 23390 elevated striatal DOPAC concentrations but higher doses were without effect; striatal dopamine and HVA overall was unaffected by administration of SCH 23390. Haloperidol did not affect basal 3H-acetylcholine release from striatal slices but reversed the apomorphine-induced inhibition of 3H-acetylcholine release. SCH 23390 did not affect basal 3H-acetylcholine release nor did it reverse the apomorphine-induced inhibition of 3H-acetylcholine release. The ability of SCH 23390 to inhibit motor behaviour in the rat may be due to its action on D-1 receptors since the drug does not cause typical changes in parameters of striatal D-2 receptor function.

Administration of cis-flupenthixol to rats for 18 months enhanced apomorphine-induced stereotyped behaviour, increased the number of specific [3H]spiperone binding sites in striatum and potentiated striatal dopamine stimulated cyclic AMP formation, but did not alter specific [3H]piflutixol binding. Following withdrawal of cis-flupenthixol intake, apomorphine-induced stereotypy returned to control values after 1 month and Bmax for [3H]spiperone binding returned to normal after 3 months. In contrast, the increased dopamine stimulated adenylate cyclase activity remained elevated 6 months after drug removal, but was normal 1 year after drug withdrawal.

The interactions of dopaminergic agonists and antagonists with 3H-antagonist labeled D1 dopamine receptors of rat striatum have been characterized. [3H]Flupentixol has been found to selectively label D1 dopamine receptors when its binding to D2 dopamine receptors is blocked by the inclusion of D2 selective concentrations of unlabeled spiroperidol or domperidone. Antagonist/3H-antagonist competition curves are of uniformly steep slope (nH = 1.0) suggesting the presence of a single D1 dopamine receptor. Agonist/3H-antagonist competition curves are extremely shallow (nH less than or equal to 0.5) for agonists of high relative efficacy, suggesting the presence of heterogeneous populations of agonist-binding states of the D1 dopamine receptor. Computer-modeling techniques were used to estimate affinities and relative site densities for these heterogeneous binding states. This analysis indicates that the ratio of agonist affinities for low and high affinity agonist-binding states is correlated with agonist relative efficacies in activating adenylate cyclase in membrane homogenates. Under the assay conditions employed, the addition of saturating concentrations of guanine nucleotides reduced, but did not abolish, the relative density of high affinity agonist-binding sites. These binding data can, at least in part, be explained by postulating two states of the D1 dopamine receptor, inducible by agonists but not by antagonists and modulated by guanine nucleotides.

The effects of age on the binding of dopaminergic ligands to rat striatal membranes were studied. When compared with four month old animals, at 22 months there was a significant decrease in the density of specific binding sites for the D-2 ligand [3H]spiperone while their affinity was unaltered. However, the specific binding of [3H]piflutixol to D-1 sites was unaltered between these age groups. The non-specific binding of [3H]piflutixol was significantly increased in aged preparations. Age-related loss of striatal D-2 dopamine receptors does not extend to the D-1 type. Alterations in non-specific [3H]piflutixol binding may reflect other pathophysiological changes associated with senescence.

The proposal that 3H-cis(Z)flupenthixol (3H-FPT) preferentially binds to striatal dopamine receptors associated with adenylate cyclase activity (D-1), distinct from dopamine receptors to which 3H-haloperidol (3H-hal) binds (D-2), has been investigated further. The dopamine agonists bromocriptine and ergotamine were 60-times more potent as displacers of 3H-hal than 3H-FPT binding. Other dopamine agonists (ergometrine, dopamine, apomorphine, 2-amino-6,7-dihydroxy-tetralin (ADTN), and ergocornine) also shared this profile, although a smaller ratio was found for these compounds. Substituted benzamides (clebopride greater than sultopride greater than sulpiride greater than metoclorpramide greater than tiapride) displace 3H-hal but have only a very slight displacing effect towards 3H-FPT, and did not inhibit dopamine-stimulated adenylate cyclase activity. The same pattern is shared by oxiperomide and molindone. Together, these results support the idea that 3H-FPT labels another class of dopamine receptors than does 3H-hal, and that the former class most likely is associated with adenylate cyclase.

Rats received either chlorpromazine (33-36 mg/kg/day), oxypertine (6.3-7.3 mg/kg/day), tetrabenazine (6.0-6.7 mg/kg/day) or reserpine (0.28-0.30 mg/kg/day) continuously for up to 12 months. Chlorpromazine and tetrabenazine reduced spontaneous locomotor activity of animals after 1 month of treatment. Thereafter, locomotor activity in animals treated with chlorpromazine returned to control levels, whereas treatment with tetrabenazine increased locomotion. Oxypertine enhanced spontaneous locomotor activity after 9 months of administration only, whereas treatment with reserpine did not alter this activity at any time during the study compared to age-matched controls. Treatment with tetrabenazine enhanced stereotyped behaviour induced by apomorphine (0.063-1.0 mg/kg s.c.) throughout the study. In contrast, stereotypy in animals administered chlorpromazine, oxypertine or reserpine was the same as in control animals throughout the 12 months of treatment. Levels of dopamine in the striatum were reduced after the first month of administration of chlorpromazine, but thereafter returned to control values. Treatment with oxypertine for up to 12 months did not alter concentrations of dopamine in the striatum, whereas administration of tetrabenazine and reserpine caused a decrease. All treatments with drugs consistently reduced the content of homovanillic acid in the striatum during the study. The Bmax for specific binding of [3H]spiperone in the striatum was increased by continuous treatment of animals with chlorpromazine, oxypertine or tetrabenazine, although the effects of oxypertine and tetrabenazine were only transient. Administration of reserpine did not alter the Bmax for specific binding of [3H]spiperone. The Bmax for specific binding of [3H]piflutixol in the striatum was unchanged by any treatment for up to 12 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Two major classes of dopamine receptors, called D-1 receptors and D-2 receptors, have been identified. [alpha-3H]Flupenthixol has been used as a radioligand for the study of D-1 receptors, which are thought to act through stimulation of adenylate cyclase activity. Previous studies in our laboratory have shown that the D-2 receptors in rat caudate labeled by [3H]spiroperidol also have a high affinity for alpha-flupenthixol. The present experiments show that although Scatchard analysis of the binding of [alpha-3H]flupenthixol is consistent with the presence of a homogeneous population of receptors, subpopulations of these sites can be distinguished by their differing affinities for spiroperidol, which has a Kd for D-1 receptors of about 0.3 microM and a Kd for D-2 receptors of approximately 50 pM. The number of D-1 receptors in rat striatum is approximately 4 times the number of D-2 receptors. D-1 receptors can be studied by including 10 nM spiroperidol in assays carried out with [alpha-3H]flupenthixol, thus blocking the binding of [alpha-3H]flupenthixol to D-2 receptors. The affinity of these receptors for dopamine is decreased by GTP, as has been observed in studies of other receptors whose effects are mediated through changes in adenylate cyclase activity. In the presence of spiroperidol, the Hill coefficients determined from dose-response curves of the inhibition of the binding of [alpha-3H]flupenthixol by antagonists or by agonists in the presence of GTP suggest that the binding reaction obeys simple Michaelis-Menten kinetics for a single class of binding sites.

The in vitro and in vivo availability of doxantrazole, a potential antiallergic compound has been evaluated. A solution was significantly less bioavailable than either tablet or suspension formulations and it is suggested that this is associated with the large volume of the solution vehicle altering the hydrophilicity of the gastrointestinal fluids. In vitro availability was determined from absorption rate constants and absorption profiles obtained using the Sartorius absorption and solubility simulators. A statistically significant correlation was found between the percentage absorbed in vitro at 1 h and both total urinary recovery and area under plasma curve values in vivo. It is considered that in vitro determination of diffusion through artificial lipid membranes may be a useful predictive method of in vivo availability.

Frozen rat striatal tissue was exposed to 10 MeV electrons from a linear accelerator. Based on the theory of target size analysis, the molecular weights of dopamine D-1 receptors (labelled by 3H-piflutixol) and dopamine D-2 receptors (labelled by 3H-spiroperidol) were 79,500 daltons and 136,700 daltons, respectively. The size of the dopamine-stimulated adenylate cyclase was 202,000 daltons. The estimated molecular sizes were deduced by reference to proteins with known molecular weights which were irradiated in parallel. The results showed that the molecular entities for 3H-piflutixol binding and 3H-spiroperidol binding were not identical. The present results do not allow conclusions as to whether D-1 and D-2 receptors are two distinct proteins in the membrane, or whether the receptors are located on the same protein. In the latter case the binding of 3H-spiroperidol needs the presence of a second molecule.

Rats received haloperidol, sulpiride, or clozapine in their daily drinking water for up to 1 year in clinically equivalent doses. After 12 months' drug intake, and while drug administration continued, striatal dopamine function was assessed. Haloperidol induced D-2 receptor hypersensitivity as shown by enhanced apomorphine-induced stereotypy, elevated Bmax for specific 3H-spiperone and 3H-NPA binding, and an increase in striatal acetylcholine content. D-1 receptor sites appeared unaffected, since dopamine-stimulated adenylate cyclase and specific 3H-piflutixol binding were not altered. In contrast, neither sulpiride nor clozapine enhanced apomorphine-induced stereotypy or increased Bmax for 3H-spiperone binding. Sulpiride, but not clozapine, increased Bmax for 3H-NPA binding; clozapine, but not sulpiride, elevated striatal acetyl choline concentrations. In general, both sulpiride and clozapine enhanced D-1 function as assessed by dopamine-stimulated adenylate cyclase or 3H-piflutixol binding. On acute administration sulpiride and clozapine appear to act at D-2 sites, but continuous chronic administration of these compounds does not result in the development of striatal D-2 receptor hypersensitivity. The absence of change in D-2 function during chronic treatment, coupled with an ability to enhance D-1 function, may contribute to the low incidence of tardive dyskinesia produced by these drugs in man.

The effects of striatal kainic acid lesions on [3H] cis-flupenthixol ([3H]FPT) and [3H]spiperone (3H-SPIP) binding to dopamine (DA) receptors in control and lesioned striata were examined. Significant reductions in both binding parameters were observed, [3H] FPT binding was depleted to a greater extent than [3H] SPIP binding. Reductions in both [3H] FPT and [3H] SPIP binding were significantly correlated with reductions in glutamic acid decarboxylase activity. After complete loss of GAD activity, 30-40% of [3H] SPIP binding sites remained in the lesioned striata, whereas all [3H] FPT binding sites were destroyed. The results are discussed in relation to the presence of distinct types of DA receptors in rat striatum, and ligand binding to these receptors.

Spectral evidence is presented that 0.01-0.03 mM solutions of the antiasthmatic drug doxantrazole contain the neutral or ionized form, depending on the solvent and, at least in 1 case, on concentration. In 1,4-dioxane, where only the neutral form exists, and in water, where the drug is ionized, no reaction between doxantrazole and calcium ion can be demonstrated spectroscopically. However, in 2-propanol at 0.01 mM and in 7:3 (v/v) 1,4-dioxane-water the doxantrazole anion can be shown to react with calcium. In more concentrated 2-propanol solutions most of the drug is in the neutral form, and no reaction with calcium is evident. It is suggested that in a biological system doxantrazole can react directly with calcium but such a reaction will depend on the state of the drug and the nature of its environment.

Administration of haloperidol (5 mg/kg i.p.), cis-flupenthixol (2.5 mg/kg i.p.) or sulpiride (2 X 100 mg/kg i.p.) daily for 21 days followed by a 3-day drug withdrawal period caused equivalent cerebral dopamine receptor supersensitivity as judged by enhanced apomorphine-induced stereotypy. These treatments also produced equivalent rises in the number of adenylate cyclase-independent dopamine receptors (D-2) in both striatal and mesolimbic tissue as assessed by specific [3H]spiperone and [3H]N,n-propylnorapomorphine (NPA) binding. No change in the dissociation constant (KD) was apparent in response to neuroleptic treatment. However, only repeated administration of cis-flupenthixol caused an increase in the number of adenylate cyclase-linked dopamine receptors (D-1) in striatum as assessed by enhanced [3H]piflutixol binding and increased dopamine-stimulated cyclic AMP formation. The dissociation constant for [3H]piflutixol binding was unchanged by cis-flupenthixol administration. No change in D-1 receptor numbers or dopamine stimulation of adenylate cyclase occurred in mesolimbic tissue. Repeated treatment with sulpiride or haloperidol was without effect on either [3H]piflutixol binding to D-1 receptors or cyclic AMP formation. In conclusion, increased apomorphine-induced stereotypy following subacute neuroleptic treatment correlates with changes in D-2 receptor numbers, but not with changes in D-1 receptors.