Blood to brain distribution of neuroleptics

Haloperidol, Olanzapine, and Risperidone Induce Morphological Changes in an In Vitro Model of Human Hippocampal Neurogenesis

BACKGROUND

Induced pluripotent stem cell (iPSC) based neuronal differentiation is valuable for studying neuropsychiatric disorders and pharmacological mechanisms at the cellular level. We aimed to examine the effects of typical and atypical antipsychotics on human iPSC-derived neural progenitor cells (NPCs).

METHODS

Proliferation and neurite outgrowth were measured by live cell imaging, and gene expression levels related to neuronal identity were analyzed by RT-QPCR and immunocytochemistry during differentiation into hippocampal dentate gyrus granule cells following treatment of low- and high-dose antipsychotics (haloperidol, olanzapine, and risperidone).

RESULTS

Antipsychotics did not modify the growth properties of NPCs after 3 days of treatment. However, the characteristics of neurite outgrowth changed significantly in response to haloperidol and olanzapine. After three weeks of differentiation, mRNA expression levels of the selected neuronal markers increased (except for MAP2), while antipsychotics caused only subtle changes. Additionally, we found no changes in MAP2 or GFAP protein expression levels as a result of antipsychotic treatment.

CONCLUSIONS

Altogether, antipsychotic medications promoted neurogenesis in vitro by influencing neurite outgrowth rather than changing cell survival or gene expression. This study provides insights into the effects of antipsychotics on neuronal differentiation and highlights the importance of considering neurite outgrowth as a potential target of action.

Application of in vitro PAMPA technique and in silico computational methods for blood-brain barrier permeability prediction of novel CNS drug candidates

Permeability assessment of small molecules through the blood-brain barrier (BBB) plays a significant role in the development of effective central nervous system (CNS) drug candidates. Since in vivo methods for BBB permeability estimation require a lot of time and resources, in silico and in vitro approaches are becoming increasingly popular nowadays for faster and more economical predictions in early phases of drug discovery. In this work, through application of in vitro parallel artificial membrane permeability assay (PAMPA-BBB) and in silico computational methods we aimed to examine the passive permeability of eighteen compounds, which affect serotonin and dopamine levels in the CNS. The data set was consisted of novel six human dopamine transporter (hDAT) substrates that were previously identified as the most promising lead compounds for further optimisation to achieve neuroprotective effect, twelve approved CNS drugs, and their related compounds. Firstly, PAMPA methods was used to experimentally determine effective BBB permeability (P_e) for all studied compounds and obtained results were further submitted for quantitative structure permeability relationship (QSPR) analysis. QSPR models were built by using three different statistical methods: stepwise multiple linear regression (MLR), partial least square (PLS), and support-vector machine (SVM), while their predictive capability was tested through internal and external validation. Obtained statistical parameters (MLR- R²_pred=-0.10; PLS- R²_pred=0.64, r²_m=0.69, r^/2_m=0.44; SVM- R²_pred=0.57, r²_m=0.72, r^/2_m=0.55) indicated that the SVM model is superior over others. The most important molecular descriptors (H₀p and SolvEMt_3D) were identified and used to propose structural modifications of the examined compounds in order to improve their BBB permeability. Moreover, steered molecular dynamics (SMD) simulation was employed to comprehensively investigate the permeability pathway of compounds through a lipid bilayer. Taken together, the created QSPR model could be used as a reliable and fast pre-screening tool for BBB permeability prediction of structurally related CNS compounds, while performed MD simulations provide a good foundation for future in silico examination.

A Novel Derivative of Thioridazine Shows Low Toxicity and Efficient Activity against Gram-Positive Pathogens

Thioridazine hydrochloride (HCl) has been suggested as a promising antimicrobial helper compound for the treatment of infections with antimicrobial-resistant bacteria. Unfortunately, the therapeutic concentration of thioridazine HCl is generally higher than what can be tolerated clinically, in part due to its toxic side effects on the central nervous system. Therefore, we aimed to synthesize a less toxic thioridazine derivative that would still retain its properties as a helper compound. This resulted in a compound designated 1-methyl-2-(2-(2-(methylthio)-10H-phenothiazin-10-yl)ethyl)-1-pentylpiperidin-1-ium bromide (abbreviated T5), which exhibited low blood–brain barrier permeability. The lowest minimal inhibitory concentration (MIC) against Staphylococcus aureus exposed to the novel compound was reduced 32-fold compared to thioridazine HCl (from 32 µg/mL to 1 µg/mL). The MIC values for T5 against five Gram-positive pathogens ranged from 1 µg/mL to 8 µg/mL. In contrast to thioridazine HCl, T5 does not act synergistically with oxacillin. In silico predictive structure analysis of T5 suggests that an acceptably low toxicity and lack of induced cytotoxicity was demonstrated by a lactate dehydrogenase assay. Conclusively, T5 is suggested as a novel antimicrobial agent against Gram-positive bacteria. However, future pharmacokinetic and pharmacodynamic studies are needed to clarify the clinical potential of this novel discovery.

d-Serine administration affects nitric oxide synthase 1 adaptor protein and DISC1 expression in sex-specific manner

Antipsychotic medications are inefficient at treating symptoms of schizophrenia (SCZ), and N-methyl d-aspartate receptor (NMDAR) agonists are potential therapeutic alternatives. As such, these agonists may act on different pathways and proteins altered in the brains of patients with SCZ than do antipsychotic medications. Here, we investigate the effects of administration of the antipsychotic haloperidol and NMDAR agonist d-serine on function and expression of three proteins that play significant roles in SCZ: nitric oxide synthase 1 adaptor protein (NOS1AP), dopamine D2 (D2) receptor, and disrupted in schizophrenia 1 (DISC1). We administered haloperidol or d-serine to male and female Sprague Dawley rats via intraperitoneal injection for 12 days and subsequently examined cortical expression of NOS1AP, D2 receptor, and DISC1. We found sex-specific effects of haloperidol and d-serine treatment on the expression of these proteins. Haloperidol significantly reduced expression of D2 receptor in male, but not female, rats. Conversely, d-serine reduced expression of NOS1AP in male rats and did not affect D2 receptor expression. d-serine treatment also reduced expression of DISC1 in male rats and increased DISC1 expression in female rats. As NOS1AP is overexpressed in the cortex of patients with SCZ and negatively regulates NMDAR signaling, we subsequently examined whether treatment with antipsychotics or NMDAR agonists can reverse the detrimental effects of NOS1AP overexpression in vitro as previously reported by our group. NOS1AP overexpression promotes reduced dendrite branching in vitro, and as such, we treated cortical neurons overexpressing NOS1AP with different antipsychotics (haloperidol, clozapine, fluphenazine) or d-serine for 24 h and determined the effects of these drugs on NOS1AP expression and dendrite branching. While antipsychotics did not affect NOS1AP protein expression or dendrite branching in vitro, d-serine reduced NOS1AP expression and rescued NOS1AP-mediated reductions in dendrite branching. Taken together, our data suggest that d-serine influences the function and expression of NOS1AP, D2 receptor, and DISC1 in a sex-specific manner and reverses the effects of NOS1AP overexpression on dendrite morphology.

Classics in Chemical Neuroscience: Haloperidol

The discovery of haloperidol catalyzed a breakthrough in our understanding of the biochemical basis of schizophrenia, improved the treatment of psychosis, and facilitated deinstitutionalization. In doing so, it solidified the role for chemical neuroscience as a means to elucidate the molecular underpinnings of complex neuropsychiatric disorders. In this Review, we will cover aspects of haloperidol's synthesis, manufacturing, metabolism, pharmacology, approved and off-label indications, and adverse effects. We will also convey the fascinating history of this classic molecule and the influence that it has had on the evolution of neuropsychopharmacology and neuroscience.

Detachment of surface membrane invagination systems by cationic amphiphilic drugs

Several cell types develop extensive plasma membrane invaginations to serve a specific physiological function. For example, the megakaryocyte demarcation membrane system (DMS) provides a membrane reserve for platelet production and muscle transverse (T) tubules facilitate excitation:contraction coupling. Using impermeant fluorescent indicators, capacitance measurements and electron microscopy, we show that multiple cationic amphiphilic drugs (CADs) cause complete separation of the DMS from the surface membrane in rat megakaryocytes. This includes the calmodulin inhibitor W-7, the phospholipase-C inhibitor U73122, and anti-psychotic phenothiazines. CADs also caused loss of T tubules in rat cardiac ventricular myocytes and the open canalicular system of human platelets. Anionic amphiphiles, U73343 (a less electrophilic U73122 analogue) and a range of kinase inhibitors were without effect on the DMS. CADs are known to accumulate in the inner leaflet of the cell membrane where they bind to anionic lipids, especially PI(4,5)P2. We therefore propose that surface detachment of membrane invaginations results from an ability of CADs to interfere with PI(4,5)P2 interactions with cytoskeletal or BAR domain proteins. This establishes a detubulating action of a large class of pharmaceutical compounds.

Drug-induced hypo- and hyperprolactinemia: mechanisms, clinical and therapeutic consequences

INTRODUCTION

The altered profiles of prolactin secretion in the anterior hypophysis, generated by pathological, pharmacological or toxicological causes, have special consequences on multiple functions in both genders.

AREAS COVERED

This selective review presents the main mechanisms controlling prolactin secretion, focusing on the interplay of various neurotransmitters or xenobiotics, but also on the role of psychic or posttraumatic stress. A detailed analysis of several pharmacotherapeutic groups with hyperprolactinemic effects emphasize on the relevance of the pharmacokinetic/pharmacodynamic mechanisms and the clinical significance of the long term administration.

EXPERT OPINION

Accurate monitoring and evaluation of the hyperprolactinemia induced by xenobiotics is strongly recommended. The typical antipsychotics and some of the atypical agents (amisulpride, risperidone, paliperidone), as well as some antidepressants, antihypertensives and prokinetics, are the most important groups inducing hyperprolactinemia. The hyperprolactinemic effects are correlated with their affinity for dopamine D2 receptors, their blood-brain barrier penetration and, implicitly, the requested dose for adequate occupancy of cerebral D2 receptors. Consequently, integration of available pharmacokinetic and pharmacodynamic data supports the idea of therapeutic switch to non-hyperprolactinemic agents (especially aripiprazole) or their association, for an optimal management of antipsychotic-induced hyperprolactinemia. Possible alternative strategies for counteracting the xenobiotics-induced hyperprolactinemia are also mentioned.

Effects of phenothiazine-class antipsychotics on the function of α7-nicotinic acetylcholine receptors

The effects of phenothiazine-class antipsychotics (chlorpromazine, fluphenazine, phenothiazine, promazine, thioridazine, and triflupromazine) upon the function of the cloned α₇ subunit of the human nicotinic acetylcholine receptor expressed in Xenopus oocytes were tested using the two-electrode voltage-clamp technique. Fluphenazine, thioridazine, triflupromazine, chlorpromazine, and promazine reversibly inhibited acetylcholine (100 μM)-induced currents with IC₅₀ values of 3.8; 5.8; 6.1; 10.6 and 18.3 μM, respectively. Unsubstituted phenothiazine did not have a significant effect up to a concentration of 30 μM. Inhibition was further characterized using fluphenazine, the strongest inhibitor. The effect of fluphenazine was not dependent on the membrane potential. Fluphenazine (10 μM) did not affect the activity of endogenous Ca²⁺-dependent Cl⁻ channels, since the extent of inhibition by fluphenazine was unaltered by intracellular injection of the Ca²⁺ chelator BAPTA and perfusion with Ca²⁺-free bathing solution containing 2 mM Ba²⁺. Inhibition by fluphenazine, but not by chlorpromazine was reversed by increasing acetylcholine concentrations. Furthermore, specific binding of [¹²⁵I] α-bungarotoxin, a radioligand selective for α₇-nicotinic acetylcholine receptor, was inhibited by fluphenazine (10 μM), but not by chlorpromazine in oocyte membranes. In hippocampal slices, epibatidine-evoked [³H] norepinephrine release was also inhibited by fluphenazine (10 μM) and chlorpromazine (10 μM). Our results indicate that phenothiazine-class typical antipsychotics inhibit, with varying potencies, the function of α₇-nicotinic acetylcholine receptor.

Effects of diverse psychopharmacological substances on the activity of brain prolyl oligopeptidase

Prolyl oligopeptidase (POP) has been connected to learning, memory and mood. Changes in serum or plasma POP activity have been linked to psychiatric disorders. POP has been thought to interfere in these conditions by cleaving neuroactive peptides or via the phosphatidylinositol second messenger system. However, little is known about the possible POP inhibition of commonly used psychoactive drugs. In this study, we measured the effects of various psychotropic drugs, including antidepressants, antipsychotics, mood stabilisers and anxiolytics, on the activity of the rat brain homogenate POP. Of the 38 compounds tested, 18 inhibited POP by at least 20% at 10 μM (buspirone, chlorpromazine, citalopram, clozapine, desipramine, duloxetine, escitalopram, flupenthixol, imipramine, ketanserin, lamotrigine, levomepromazine, prazosin, prochlorperazine, promazine, risperidone ritanserin and thioridazine). Thioridazine and valproate (VPA) acted at therapeutic plasma levels. Kinetically, VPA was a competitive inhibitor, thioridazine a non-competitive inhibitor and ketanserin a mixed type inhibitor. Being lipophilic, many of the psychoactive compounds are present in the brain at several-times higher concentrations than in plasma. At concentrations reported to be reached in the brain, chlorpromazine, clozapine, desipramine, imipramine, prochlorperazine and promazine inhibited POP by 30-50% suggesting that they could inhibit POP in vivo. However, when studied ex vivo, a single dose of 10 mg/kg thioridazine caused a deep sedation in the mice but did not inhibit the activity of POP. In conclusion, compared with conventional POP inhibitors, all psychopharmacological compounds tested are very weak inhibitors in vitro, and we doubt that their POP inhibition would be therapeutically meaningful.

Effects of quetiapine, risperidone, 9-hydroxyrisperidone and ziprasidone on the survival of human neuronal and immune cells in vitro

Because there are reports on cytotoxic and cytoprotective effects of antipsychotics, the aim of the present study was to evaluate the impacts of different concentrations (1.6-50 microg/mL) of atypical antipsychotics on the survival of human neuronal (neuroblastoma SH-SY5Y) and immune (monocytic U-937) cells and on energy metabolism (ATP level after the incubation with antipsychotics in the concentration of 25 microg/mL). Statistical analysis showed that incubation for 24 h with the antipsychotics quetiapine, risperidone, 9-hydroxyrisperidone and ziprasidone led to a significantly enhanced cell survival in both cell lines in the lower concentrations. Higher concentrations exerted in part cytotoxic effects with the exception of quetiapine, but therapeutically relevant concentrations of the drugs were not cytotoxic in our experiments. Measurement of ATP contents in the neuronal cell line showed significantly increased levels after a 24-h treatment with 25 microg/mL risperidone and 9-hydroxyrisperidone. The other substances produced no effects. Our results show that the antipsychotic substances under investigation exert concentration-dependent effects on cell survival in both cell lines examined.

Effects of haloperidol, clozapine and olanzapine on the survival of human neuronal and immune cells in vitro

Cytotoxic effects on neuronal as well as on immune cells have been reported for both typical and atypical antipsychotic drugs. We evaluated the effects of different concentrations of a typical (haloperidol) and two atypical (clozapine, olanzapine) antipsychotics on the survival of human neuronal (SH-SY5Y cells) and immune cells (U937 cells) by determining the metabolic activity after 24 h of incubation by the modified tetrazolium method. The dopaminergic neuroblastoma SH-SY5Y and the lymphoma U-937 cell line are well established models for in vitro investigations. To further elucidate possible mechanisms of action we also determined the ATP content in the cultured cells. After experimental treatment, significant effects were detected by Kruskal Wallis test for all treatment conditions. Post-hoc tests (Dunn's method) showed that haloperidol and clozapine at the two highest concentrations (25 and 50 microg/ml) caused a significant decrease of metabolic activity in both cell systems, which was also detectable after treatment with clozapine at a concentration of 12.5 microg/ml in U937 cells. In contrast, olanzapine induced a significant increase in metabolic activity of SH-SY5Y cells at all concentrations except for the concentration of 3.1 microg/ml, whereas the metabolic activity in U937 cells was increased at concentrations of 1.6 and 6.25 microg/ml. For the determination of ATP content, the LD(50) values of the metabolic activity were used, except for olanzapine for which no distinct LD(50) value was available. Significant changes were detected for all treatments and post-hoc tests revealed that haloperidol caused a significant decrease compared to the control condition in both cell systems. These findings suggest that antipsychotic substances of different classes exert differential metabolic effects in both neuronal and immune cell systems.

Sensitive liquid chromatography/tandem mass spectrometry method for the simultaneous determination of olanzapine, risperidone, 9-hydroxyrisperidone, clozapine, haloperidol and ziprasidone in rat brain tissue

One prerequisite for therapeutic effects of psychiatric drugs is the ability to pass the blood brain barrier. Hence, it is important to know the concentration of antipsychotic drugs in brain tissue. In general, determinations of lipophilic compounds from lipophilic matricies such as the brain are a challenge. Here we have adapted a plasma assay for antipsychotics for the target organ the brain. Using modified sample preparation and chromatographic strategies, the analytes were extracted from rat brain homogenate and analyzed by LC-MS/MS. The method used a Waters Atlantis dC-18 (30 mm x 2.1 mm i.d., 3 microm) column with a mobile phase of acetonitrile/5 mM ammonium formate (pH 6.1 adjusted with formic acid) and gradient elution. All analytes were detected in positive ion mode using multiple-reaction monitoring. The method was validated and the linearity, lower limit of quantitation, precision, accuracy, recoveries, specificity and stability were determined. This method was then successfully used to quantify the rat brain tissue concentration of the analytes after chronic treatment with these antipsychotic drugs.

Chemo brain - a psychotropic drug phenomenon?

The phenomenon of 'chemo brain' refers to a cluster of potentially long-lasting, cognitive deficiencies which are caused by systemic cancer treatments. While the oncology community has gradually acknowledged the existence of chemo brain as an unintended consequence of anti-neoplastic therapies, other fields of medicine have been less astute. Preliminary research evidence has suggested a role for many existing psychopharmaceuticals in fighting malignancies, based upon the capacity of these drugs to modify gene expression, cell turnover, and cell death (e.g., apoptosis). The author presents the hypothesis that the same mechanisms which suppress the growth and survival of cancer cells may pose similar hazards to non-diseased neurons, thereby inducing the cognitive changes which oncologists have come to associate with chemo brain. The article discusses the specific examples of valproic acid, clomipramine, and fluoxetine as treatments for solid tumors, primary brain tumors, and Burkitt's lymphoma, respectively. Clinicians, regardless of specialization, are encouraged to consider the potential reality of psychotropic chemo brain, in order to avoid or limit the use of medications which cause it, and in order to prioritize the delivery of rehabilitative strategies in an effort to mitigate or reverse its features.

Antipsychotics inhibit TREK but not TRAAK channels

Schizophrenia is a chronic mental illness affecting 0.4% of the population. Existing antipsychotic drugs are mainly used to treat positive symptoms such as hallucinations but have only poor effects on negative symptoms such as cognitive deficits or depression. TREK and TRAAK channels are two P domain background potassium channels activated by polyunsaturated fatty acids and mechanical stress. TREK but not TRAAK channels are regulated by Gs- and Gq-coupled pathways. The inactivation of the TREK-1 but not the TRAAK channel in mice results in a depression-resistant phenotype. In addition, it has been shown that antidepressants such as fluoxetine or paroxetine directly inhibit TREK channel activity. Here we show that different antipsychotic drugs directly inhibit TREK currents with IC(50) values of approximately 1 to approximately 20 microM. No effect is seen on TRAAK channel activity. We conclude that TREK channels might be involved in the therapeutic action of antipsychotics or in their secondary effects. Furthermore, TREK channels could play a role in the pathophysiology of psychiatric disorders such as depression and schizophrenia.

Effects of acute and subchronic d-amphetamine on ventral striatal concentrations of neurotensin and neuropeptide Y in rats treated with antipsychotic drugs

We have reported that acute d-amphetamine increases extracellular concentrations (efflux) of neurotensin-like immunoreactivity (NT-LI) and neuropeptide Y-LI (NPY-LI) in the ventral striatum (VSTR) of freely moving rats, effects that are abolished by chronic administration of haloperidol and risperidone admixed to food pellets. In this study we further investigated the d-amphetamine effects on NT-LI and NPY-LI efflux in VSTR and their content in selected brain regions. Rats received haloperidol, risperidone or vehicle for 30days and saline or d-amphetamine either on days 22-29 and/or day 30. Seven day d-amphetamine administration decreased basal NT-LI and NPY-LI efflux in vehicle-treated rats; pretreatment with haloperidol counteracted these effects, while pretreatment with risperidone had effect only on NT-LI. Acute d-amphetamine after the seven day d-amphetamine increased NT-LI only. Pretreatment with haloperidol or risperidone abolished the effects of acute d-amphetamine on NT-LI and NPY-LI. Acute and seven day d-amphetamine increased NT-LI and NPY-LI contents in striatum; seven day d-amphetamine also increased NT-LI in frontal and occipital cortex and both NT-LI and NPY-LI in hippocampus. Our results suggest that NT and NPY are involved in both the pathophysiology and the therapeutics of schizophrenia.

The neuroleptic drug, fluphenazine, blocks neuronal voltage-gated sodium channels

Fluphenazine (Prolixin(R)) is a potent phenothiazine-based dopamine receptor antagonist, first introduced into clinical practice in the late 1950s as a novel antipsychotic. The drug emerged as a 'hit' during a routine ion channel screening assay, the present studies describe our electrophysiological examination of fluphenazine at tetrodotoxin-sensitive (TTX-S) and resistant (TTX-R) voltage-gated sodium channel variants expressed in three different cell populations. Constitutively expressed TTX-S conductances were studied in ND7/23 cells (a dorsal root ganglion-derived clonal cell line) and rat primary cerebrocortical neurons. Recombinant rat Na(V)1.8 currents were studied using ND7/23 cells as a host line for heterologous expression. Sodium currents were examined using standard whole-cell voltage-clamp electrophysiology. Current-voltage relationships for either ND7/23 cell or Na(V)1.8 currents revealed a prominent fluphenazine block of sodium channel activity. Steady-state inactivation curves were shifted by approximately 10 mV in the hyperpolarizing direction by fluphenazine (3 microM for ND7/23 currents and 10 microM for Na(V)1.8), suggesting that the drug stabilizes the inactivated channel state. Fluphenazine's apparent potency for blocking either ND7/23 or Na(V)1.8 sodium channels was increased by membrane depolarization, corresponding IC(50) values for the ND7/23 cell conductances were 18 microM and 960 nM at holding potentials of -120 mV and -50 mV, respectively. Frequency-dependent channel block was evident for each of the cell/channel variants, again suggesting a preferential binding to inactivated channel state(s). These experiments show fluphenazine to be capable of blocking neuronal sodium channels. Several unusual pharmacokinetic features of this drug suggest that sodium channel block may contribute to the overall clinical profile of this classical neuroleptic agent.

Neuroleptic drugs in the human brain: clinical impact of persistence and region-specific distribution

After discontinuation of neuroleptic agents, their effects are still present for a long time. The exact underlaying mechanisms are still unclear. In two previous studies we measured the concentrations and region-specific distribution of haloperidol (Kornhuber et al. 1999) and levomepromazine (Kornhuber et al. 2006) in postmortem human brain tissues. The aim of the present paper is to compare the results of these two studies. Even after short-term treatment, haloperidol and levomepromazine concentrations reach high levels in human brain tissue. Haloperidol concentrations in brain tissue are 10-30 times higher than the optimum serum concentrations in the treatment of schizophrenia. The brain-to-blood concentration ratio of levomepromazine is about 10. The estimated elimination half-life of these drugs in brain tissue are 6.8 days (haloperidol), 7.9 days (levomepromazine) and 27.8 days for the metabolite desmethyl-levomepromazine, respectively. After two half-lives (about 2 weeks), a considerable amount of drug remains in brain tissue. Haloperidol concentrations appeared to be homogeneously distributed across different brain areas, whereas levomepromazine shows a region-specific distribution, with highest values in the basal ganglia. The persistence of neuroleptic drugs in the human brain might explain their prolonged effects and side effects. The region-specific distribution of levomepromazine may increase our understanding of both the preferential toxicity of neuroleptic drugs against basal ganglia structures and higher basal ganglia volumes in patients treated with neuroleptics.

A recursive-partitioning model for blood–brain barrier permeation

A series of bagged recursive partitioning models for log(BB) is presented. Using a LGO-CV, three sets of physical property descriptors are evaluated and found to have Q2 values of 0.51 (CPSA), 0.53 (Ro5x) and 0.53 (MOE). Extrapolating these models to Pfizer chemical space is difficult due to P-glycoprotein (P-gp) mediated efflux. Low correlation coefficients for this test set are improved (R2 = 0.39) when compounds known to be P-gp substrates or statistical extrapolations are removed. The use of simple linear models for specific chemical series is also found to improve the correlation over a limited chemical space.

Modulation of striatal dopamine release in vitro by agonists of the glycineB site of NMDA receptors; interaction with antipsychotics

The N-methyl-D-aspartate (NMDA) glutamate receptor possesses an obligatory co-agonist site for D-serine and glycine, named the glycineB site. Several clinical trials indicate that glycineB agonists can improve negative and cognitive symptoms of schizophrenia when co-administered with antipsychotics. In the present study we have investigated the effects of glycineB agonists on the endogenous release of dopamine from preparations of rat striatal tissue prisms in static conditions. The glycineB agonists glycine (1 mM) and D-serine (10 microM), but not D-cycloserine (10 microM), substantially increased the spontaneous release of dopamine, but significantly reduced the release of dopamine evoked by NMDA. The effect of glycine on spontaneous release was abolished by the non-competitive NMDA antagonists 5R,10S-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d] cyclohepten-5,10-imine (MK-801, 10 microM) and ifenprodil (5 microM), but was only partially suppressed by the competitive antagonist 4-(3-phosphonopropyl)-piperazine-2-carboxylic acid (CPP, 10 microM). The selective inhibitor of the glial glycine transporter GlyT1 N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine (NFPS, 10 microM) significantly increased the release of dopamine in an MK-801-sensitive manner. Interestingly, haloperidol (1 microM), but not clozapine (10 microM), prevented the effects of glycine. This study shows that glycineB modulators can control dopamine release by interacting with a distinctive NMDA receptor subtype with which some typical antipsychotics can interfere.

Region specific distribution of levomepromazine in the human brain

OBJECTIVE

The aim of this study was to examine concentrations of levomepromazine and its metabolite desmethyl-levomepromazine in different regions of human brain and in relationship to drug-free time.

METHODS

Drug concentrations were measured in up to 43 regions of 5 postmortem human brains of patients previously treated with levomepromazine. To enable statistical comparison across brain regions several smaller brain areas were put together to form larger brain areas (cortex cerebri, limbic system, cerebellum, basal ganglia, thalamus). Mean values of drug concentrations in these larger brain areas were used in a repeated measurement ANOVA to analyze for region specific distribution. The elimination half-life in brain tissue was estimated with a NONMEM population kinetic analysis using the mean value of all brain regions of an individual case.

RESULTS

Levomepromazine and desmethyl-levomepromazine appear to accumulate in human brain tissue relative to blood. Mean concentrations differed largely between individual brains, in part due to differences in dose of drug, duration of treatment and drug-free time before death. There was an apparent region-specific difference in levomepromazine concentrations with highest values in the basal ganglia (mean 316 ng/g) and lowest values in the cortex cerebri (mean 209 ng/g). The elimination half-life from brain tissue is longer than from blood and was calculated to be about one week. Similar results were obtained with desmethyl-levomepromazine.

CONCLUSIONS

Levomepromazine shows a region-specific distribution in the human brain with highest values in the basal ganglia. This might be the consequence of low expression of the metabolic enzyme Cyp2D6 in the basal ganglia. If this finding is true also for other neuroleptic drugs it might increase our understanding of preferential toxicity of neuroleptic drugs against basal ganglia structures and higher volumes of basal ganglia of neuroleptic-treated patients. Furthermore, patients exposed to levomepromazine cannot be considered to be free of residual effects of the drug for a number of weeks after withdrawal.

The influence of psychotropic drugs on cerebral cell death: female neurovulnerability to antipsychotics

Tissue transglutaminase (tTG) is a marker for apoptosis, and its protein level is known to be increased in post-mortem Alzheimer's and Huntington's disease brains. tTG is increased in the cerebrospinal fluid of patients with Alzheimer's disease. However, the influence of psychotropic medication on acute cell death has not been studied so far in vivo, although some experiments performed in vitro suggest that antipsychotic drugs are neurotoxic. The protein level of tTG was examined in the cerebrospinal fluid obtained from 29 patients under neuroleptic medication in the last 24 h before lumbar puncture (eight patients diagnosed with Alzheimer's disease and 21 patients with other neurological diseases), and compared with those from 55 patients without antipsychotic medication (25 Alzheimer's patients and 30 others). In addition, the influence of several other psychotropic drugs on apoptosis was analysed. A significant influence (P<0.01) of antipsychotic drugs for both the Alzheimer's and the non-Alzheimer's group was found with respect to tTG protein levels in cerebrospinal fluid. By contrast to the male subgroups, the female groups showed a strong influence of neuroleptics on cerebral cell death. Surprisingly, atypical antipsychotics did not differ from typical neuroleptics in neurotoxicity. By contrast, no influence of antidepressants, cholinesterase-inhibitors, nootropics, tranquilizers and tramadol on cerebral cell death was found. The results suggest that typical and atypical antipsychotic drugs may induce cerebral cell death, especially in female patients. Subjects with Alzheimer's disease might be even more vulnerable to any antipsychotic. Therefore, subsequent research should aim to identify atypical neuroleptics without neurotoxicity. A limit on the use of first- and second-generation antipsychotics in elderly patients is proposed. Finally, the possible connection between the observed increased cerebral cell death and tardive dyskinesia, the most threatening side-effect in antipsychotic therapy, is discussed.

Antipsychotic drugs antagonize human serotonin type 3 receptor currents in a noncompetitive manner

The serotonin type 3 (5-HT(3)) receptor is the only ligand-gated ion channel receptor for serotonin (5-HT). 5-HT(3) receptors play an important role in modulating the inhibitory action of dopamine in mesocorticolimbic brain regions. Neuroleptic drugs are commonly thought to exert their psychopharmacological action mainly through dopamine and serotonin type 2 (5-HT(2)) receptors. Except for clozapine, a direct pharmacological interaction of neuroleptics with 5-HT(3) receptors has not yet been described. Using the concentration-clamp technique, we investigated the effects of flupentixol, various phenothiazines, haloperidol, clozapine and risperidone on Na(+)-inward currents through 5-HT(3) receptors stably expressed in human embryonic kidney 293 cells, and through endogenous 5-HT(3) receptors of murine N1E-115 neuroblastoma cells. In addition, we studied their effects on Ca(2+) influx, measured as a change in intracellular Ca(2+) concentrations ([Ca(2+)](i)). All neuroleptic drugs, but not risperidone, antagonized Na(+)- and Ca(2+)-inward currents evoked by 5-HT (10 microM for 2 s and 1 microM, respectively) in a voltage-independent manner. Only clozapine was a competitive antagonist, while all other compounds turned out to be noncompetitive. Fluphenazine and haloperidol affected membrane anisotropy at concentrations below their IC(50) values, indicating that a change in membrane anisotropy might contribute to their antagonistic effect at the 5-HT(3) receptor. Only structure analogues of flupentixol and fluphenazine with a lipophilic side chain were potent antagonists against 5-HT-evoked Na(+) and Ca(2+) currents. Since 5-HT(3) receptors modulate mesolimbic and mesocortical dopaminergic activity, the functional antagonism of neuroleptics at 5-HT(3) receptors may contribute to their antipsychotic efficacy and may constitute a not yet recognized pharmacological principle of these drugs.

Determination of myocardium to plasma concentration ratios of five antipsychotic drugs: comparison with their ability to induce arrhythmia and sudden death in clinical practice

Reviewing available data shows that most of antipsychotic drugs are associated with arrhythmia and sudden death. Experimental studies have shown a HERG channel blockade, a dose-dependent increase in duration of action potential or of QT interval, with various degrees of indicators of serious arrhythmogenicity. However, it seems difficult to relate these in vitro and in vivo preclinical models to clinical findings, in part, because the relationship between concentrations used and in vivo tissue concentrations during treatment in man is not known. Consequently, we established the myocardium to plasma concentration ratios for a series of antipsychotic drugs by intraperitoneal administration of different level doses to the guinea pig. Then, we compared these values to their ability to induce arrhythmia or torsade de pointes in clinical practice. The myocardium to plasma concentration ratios were 2.2 for clozapine, 2.7 for olanzapine, 3.1 for sertindole, 4.5 for risperidone, and 6.4 for haloperidol. These data suggest that when the ratio is higher than 4, arrhythmia and sudden death may be expected. On the contrary, when the ratio is less than 3, little effect may be predicted. These results underscore the importance of interpreting HERG channel data and electrophysiological data in the context of other pharmacokinetic parameters such as myocardium to plasma distribution.

Correlation and prediction of a large blood-brain distribution data set--an LFER study

We report linear free energy relation (LFER) models of the equilibrium distribution of molecules between blood and brain, as log BB values. This method relates log BB values to fundamental molecular properties, such as hydrogen bonding capability, polarity/polarisability and size. Our best model of this form covers 148 compounds, the largest set of log BB data yet used in such a model, resulting in R(2)=0.745 and e.s.d.=0.343 after inclusion of an indicator variable for carboxylic acids. This represents rather better accuracy than a number of previously reported models based on subsets of our data. The model also reveals the factors that affect log BB: molecular size and dispersion effects increase brain uptake, while polarity/polarisability and hydrogen-bond acidity and basicity decrease it. By splitting the full data set into several randomly selected training and test sets, we conclude that such a model can predict log BB values with an accuracy of less than 0.35 log units. The method is very rapid-log BB can be calculated from structure at a rate of 700 molecules per minute on a silicon graphics O(2).

Antipsychotic radioreceptor assay: a modification identifying selective receptor effects

Radioreceptor assays offer the advantage of a single assay that can assess uniform exposure to multiple chemical compounds. The advent of atypical antipsychotic agents has led to new awareness of the multiple receptor subtypes through which antipsychotic agents may exert their effects, and a renewed interest in comparative drug trials of antipsychotics. The objective of this study was to show the development and validation of antipsychotic radioreceptor assays using clonal cell lines stably expressing isolated human receptors. Model assays were developed using the dopamine(2) (D(2)) and D(4) receptors. D(2) and D(4) activities measured by radioreceptor assay in plasma of antipsychotic-treated subjects were highly correlated with high-performance liquid chromatography determinations of antipsychotic concentrations. Similarly, for a variety of typical and atypical antipsychotic agents, the quotients of D(4)/D(2) activity in plasma of antipsychotic-treated subjects were highly correlated with the quotients of D(4)/D(2) affinities of these agents. Valid receptor-selective antipsychotic assays can be established and may have utility for dissecting the in vivo activity of atypical antipsychotics in relation to specific outcomes in clinical trials.

Haloperidol-induced neuronal apoptosis: role of p38 and c-Jun-NH(2)-terminal protein kinase

We examined patterns and mechanisms of cell death induced by haloperidol. Cortical cell cultures exposed to 10-100 microM: haloperidol for 24 h underwent neuronal death without injuring glia. The degenerating neurons showed hallmarks of apoptosis, featuring cell body shrinkage, nuclear chromatin condensation and aggregation, nuclear membrane disintegration with intact plasma membrane, and prominent internucleosomal DNA fragmentation. Neither glutamate antagonists nor antioxidants prevented the haloperidol-induced neuronal apoptosis. The c-Jun-NH(2)-terminal protein kinase and p38 mitogen-activated protein kinase were activated within 1 h and were sustained over the next 3 h following exposure of cortical neurons to 30 microM haloperidol. Haloperidol-induced neuronal apoptosis was partially attenuated by 10-30 microM PD169316, a selective inhibitor of p38 mitogen-activated protein kinase. Inclusion of 1 microg/ml cycloheximide, a protein synthesis inhibitor, or 100 ng/ml insulin prevented activation of both kinases and subsequent neuronal death. The present study demonstrates that cortical neurons exposed to haloperidol undergo apoptosis depending on activation of p38 mitogen-activated protein kinase and c-Jun-NH(2)-terminal protein kinase sensitive to cycloheximide and insulin.

Inhibition by various antipsychotic drugs of the G-protein-activated inwardly rectifying K(+) (GIRK) channels expressed in xenopus oocytes

To investigate the effects of various chemical classes of antipsychotic drugs: haloperidol, thioridazine, pimozide and clozapine, on the G-protein-activated inwardly rectifying K(+) (GIRK) channels, we carried out Xenopus oocyte functional assays with GIRK1 and GIRK2 mRNAs or GIRK1 and GIRK4 mRNAs. In oocytes co-injected with GIRK1 and GIRK2 mRNAs, application of each of the various antipsychotic drugs immediately caused a reduction of inward currents through the basally active GIRK channels. These responses were not observed in the presence of 3 mM Ba(2+), which blocks the GIRK channels. In addition, in uninjected oocytes, none of the drugs tested produced any significant current response. These results indicate that all the antipsychotic drugs tested inhibited the brain-type GIRK1/2 heteromultimeric channels. Furthermore, similar results were obtained in oocytes co-injected with GIRK1 and GIRK4 mRNAs, indicating that the antipsychotic drugs also inhibited the cardiac-type GIRK1/4 heteromultimeric channels. All the drugs tested inhibited, in a concentration-dependent manner, both types of GIRK channels with varying degrees of potency and effectiveness at micromolar concentrations. Only pimozide caused slight inhibition of these channels at nanomolar concentrations. We conclude that the various antipsychotic drugs acted as inhibitors at the brain-type and cardiac-type GIRK channels. Our results suggest that inhibition of both types of GIRK channels by these drugs underlies some of the side effects, in particular seizures and sinus tachycardia, observed in clinical practice.

Pharmacokinetics and tissue distribution of olanzapine in rats

The single dose pharmacokinetics of olanzapine in rats, following an oral dose and its distribution in the brain and other tissues after repeated oral and intra-peritoneal (i.p.) administration, were studied. Olanzapine in plasma, brain, liver, lung, kidney, spleen and fat was assayed at predose, 0.25, 0.5, 1, 2, 5, 12, 24, 36, 48 h postoral dose of 6 mg/kg and after daily oral and i.p. doses of 0.25, 1, 3, and 6 mg/kg/day of olanzapine for 15 consecutive days by a sensitive and specific HPLC method with electrochemical detection. Olanzapine was readily absorbed and distributed in plasma and tissues as the peak concentrations were reached within approximately 45 min after the oral dose. The terminal half-life of olanzapine in plasma was 2.5 h and in tissues it ranged from 3 to 5.2 h. The area under the concentration-time curve (AUC(last)) was lowest in plasma and largest in liver and lung. The AUC(last) of olanzapine was eight times larger in brain and three to 32 times larger in other tissues than that in plasma. After repeated oral doses, the plasma and tissue concentrations of olanzapine were generally higher than those after repeated i.p. doses. The liver and spleen had the highest concentrations after oral and i.p doses, respectively. In both cases, the tissue concentrations were four- to 46-fold higher than that in plasma and correlated with administered doses. Likewise, plasma concentrations strongly correlated with the simultaneous brain and tissue concentrations (r(2)>0.908, p<0.0001). On average, the brain levels were 6.3-13.1 and 5.4-17.6 times higher than the corresponding plasma level after oral and i.p. doses, respectively. The tissue to plasma level ratio of olanzapine was higher in other tissues. The data indicated that olanzapine is rapidly absorbed and widely distributed in the tissues of rats after oral and i.p. administration. The plasma concentration appears to predict the simultaneous concentration in brain and other tissues. There was no marked localized accumulation of olanzapine in any of the regions of the rat brain.

The effect of haloperidol on the histaminergic neuron system in the rat brain

In this study, the effect of haloperidol on histamine (HA) levels, histidine decarboxylase (HDC) activities and the bindings of [3H]-(R)-alpha-methylhistamine ([3H]-(R)-alpha-MeHA) to histamine H3 receptors were investigated in the rat brain. Administration of 10 mg/kg of haloperidol decreased HA levels in the rat striatum and diencephalon, but increased HDC activities in rat striatum and diencephalon, although that of 5 mg/kg did not change them. Meanwhile, haloperidol inhibited the bindings of [3H]-(R)-alpha-MeHA to H3 receptor sites in the rat striatal membrane with a Ki value of 10.5 +/- 0.45 microM. These findings suggest that only a high dose of haloperidol increases HA synthesis and release as a histamine H3 receptor antagonist in the rat brain.

Relationship between immobilised artificial membrane chromatographic retention and the brain penetration of structurally diverse drugs

Retention factors were determined for a set of 26 drugs, for which brain/blood concentration data are available, using immobilised artificial membrane (IAM) chromatography. The compound set represented acidic, basic and neutral drugs from various structural classes. The relationship between IAM retention and lipophilicity (n-octanol-water partition coefficient Koct), molecular size and acid/base character of the drugs and the relationship between brain distribution and IAM retention and the other parameters were analysed. IAM retention was increased with increases in lipophilicity and solute size, and decreased by the ionisation of acidic groups. Ionisation of basic groups had no significant effect. A three-parameter regression model with log Koct, molecular weight and an indicator parameter for the presence of carboxyl group explained 93% of the variation in log kIAM. The concentration ratio between brain and blood (log BB) was only weakly correlated with the IAM chromatographic retention or n-octanol-water partitioning. Three-parameter models taking ionisation and size into account, in addition to either log Koct or log kIAM, explained about 85% of the variation of log BB in the test set. Although IAM chromatography offers no advantage in these models, it seems to provide a better model than n-octanol-water partitioning for the membrane distribution of ionised compounds.

Prolactin plasma levels and D2-dopamine receptor occupancy measured with IBZM-SPECT

By the application of 123([123I]IBZM), an iodine-labelled dopamine D2-receptor antagonist, brain D2 receptors in humans can be visualized with single photon emission computed tomography (SPECT). The ratio of IBZM binding to striatal regions versus binding to frontal cortex (ST/FC ratio) provided a semiquantitative measurement of D2 receptor binding in the striatum. This study investigated the relationship between receptor occupancy and plasma prolactin levels in 12 male patients treated with haloperidol, benperidol or clozapine. Prolactin levels were positively correlated with D2 receptor occupancy, reflecting at least in part a comparable dopamine receptor antagonism in different dopaminergic pathways.

Detection of psychoactive drugs using 19F MR spectroscopy

In vivo 19F resonance spectroscopy measurements of trifluorinated neuroleptics (fluphenazine and trifluoperazine) and later trifluorinated antidepressants (fluoxetine and fluvoxamine) began with animal experiments in 1983. Using rats which have been treated with high oral doses of fluphenazine over a period of three weeks in the beginning of these experiments the measurement time was very long (up to 10 h). The application of better techniques using surface coils led to marked improvement of the signal noise ratio and measurement times in animal experiments could be reduced to minutes. These results encouraged us and other groups to perform experiments in humans to detect and try to estimate brain levels of trifluorinated neuroleptics and antidepressants. The present data of several research groups demonstrate that 19F MR spectroscopy has the potential of becoming a valuable tool for monitoring drug levels at the site of action. The extension of the animal studies to humans might facilitate a better treatment of schizophrenic and depressive patients.

Chronic haloperidol, but not clozapine, produces altered oral movements and increased extracellular glutamate in rats

Rats administered chronic haloperidol or clozapine in their drinking water for 6 months were monitored for changes in oral movements using a computerized video analysis system. Haloperidol-treated animals exhibited late onset increases in small amplitude oral movements and an increase in the percentage of oral movements in the 1-2 Hz range, accompanied by a decrease in oral movements in the higher frequency range (> 6 Hz) as determined by fast fourier analysis. In contrast, clozapine-treated rats showed a decrease in medium-sized amplitude oral movements, but did not demonstrate significant changes in the distribution of oral movements across frequencies. Extracellular concentrations of gamma-aminobutyric acid (GABA) and glutamate in the ventrolateral striatum were then assessed by intracranial microdialysis during oral drug administration and 3 days after drug withdrawal. Extracellular GABA and glutamate levels were not significantly different between groups during drug administration. However, 3 days after drug withdrawal, there was a significant increase in glutamate in the haloperidol-treated rats. No changes were noted for glutamate levels in clozapine-treated rats or for GABA levels in either group following withdrawal. These results confirm the atypical profile of clozapine in an animal model of tardive dyskinesia and suggest that alterations in striatal glutamatergic function follow typical, but not atypical, antipsychotic drug administration.

Regional brain distribution of risperidone and its active metabolite 9-hydroxy-risperidone in the rat

Risperidone is a new benzisoxazole antipsychotic. 9-Hydroxy-risperidone is the major plasma metabolite of risperidone. The pharmacological properties of 9-hydroxy-risperidone were studied and appeared to be comparable to those of risperidone itself, both in respect of the profile of interactions with various neurotransmitters and its potency, activity, and onset and duration of action. The absorption, plasma levels and regional brain distribution of risperidone, metabolically formed 9-hydroxy-risperidone and total radioactivity were studied in the male Wistar rat after single subcutaneous administration of radiolabelled risperidone at 0.02 mg/kg. Concentrations were determined by HPLC separation, and off-line determination of the radioactivity with liquid scintillation counting. Risperidone was well absorbed. Maximum plasma concentrations were reached at 0.5-1 h after subcutaneous administration. Plasma concentrations of 9-hydroxy-risperidone were higher than those of risperidone from 2h after dosing. In plasma, the apparent elimination half-life of risperidone was 1.0 h, and mean residence times were 1.5 h for risperidone and 2.5 h for its 9-hydroxy metabolite. Plasma levels of the radioactivity increased dose proportionally between 0.02 and 1.3 mg/kg. Risperidone was rapidly distributed to brain tissues. The elimination of the radioactivity from the frontal cortex and striatum--brain regions with high concentrations of 5-HT2 or dopamine-D2 receptors--became more gradual with decreasing dose levels. After a subcutaneous dose of 0.02 mg/kg, the ED50 for central 5-HT2 antagonism in male rats, half-lives in frontal cortex and striatum were 3-4 h for risperidone, whereas mean residence times were 4-6 h for risperidone and about 12 h for 9-hydroxy-risperidone. These half-lives and mean residence times were 3-5 times longer than in plasma and in cerebellum, a region with very low concentrations of 5-HT2 and D2 receptors. Frontal cortex and striatum to plasma concentration ratios increased during the experiment. The distribution of 9-hydroxy-risperidone to the different brain regions, including frontal cortex and striatum, was more limited than that of risperidone itself. This indicated that 9-hydroxy-risperidone contributes to the in vivo activity of risperidone, but to a smaller extent than would be predicted from plasma levels. AUCs of both active compounds in frontal cortex and striatum were 10-18 times higher than those in cerebellum. No retention of metabolites other than 9-hydroxy-risperidone was observed in any of the brain regions investigated.

Phenothiazine treatment and respiratory distress syndrome in a child

An 11-year-old boy who was treated with a relatively high dose of methotrimeprazine meleate (Levemepromazine) a phenothiazine antipsychotic drug, was admitted to the pediatric intensive care unit suffering from respiratory distress syndrome. He required intensive treatment and support for 13 days. The persistent effects of methotrimeprazine meleate on various organs are typical of the prolonged biological action of the phenothiazine metabolites. The association of phenothiazine overdose and respiratory distress syndrome merits consideration.

Drug distribution between blood and brain as a determinant of antipsychotic drug effects

Concentrations of the neuroleptics haloperidol, bromperidol, fluphenazine, chlorpromazine and its metabolites nor-1- and nor-2-chlorpromazine, thioridazine and its metabolites mesoridazine, sulforidazine, and northioridazine, and promazine were estimated in serum and brain of rats by high performance liquid chromatography (HPLC) with electrochemical detection following 5 days of chronic administration of drug at typical doses (haloperidol, bromperidol, and fluphenazine 1 mg/kg/day; chlorpromazine, promazine, and thioridazine 25 mg/kg/day). The observed ratio of brain-to-serum concentration of drug varied widely (0.18-62.5) among neuroleptics studied. High potency agents had more favorable brain-to-blood distribution than low potency agents, and a strong correlation (r = 0.734, p < 0.05) was observed between the brain-to-serum ratios of the neuroleptics and standard clinical doses of drug. This finding suggests that drug distribution is a significant determinant of clinical potency. For most neuroleptics, including drugs with high (fluphenazine, haloperidol) and low potency (thioridazine) such as dopamine D2 antagonists, concentration of drug in the brain was similar. If the results are applicable to patients, they suggest that the degree of dopamine D2 blockade achieved during treatment may vary by drug. Chlorpromazine and promazine were notable for producing high concentrations of drug in the brain at typical doses, suggesting that optimal doses might be lower than those in common use. These results may be important in designing and interpreting studies of the effects of neuroleptic drugs in animals and patients.

Regional differences in chronic neuroleptic effects on extracellular dopamine activity

The extracellular levels of dopamine (DA) and DA metabolites in the caudate-putamen (CPu) and the nucleus accumbens (NA) of rats following administration of haloperidol (HAL) decanoate and fluphenazine (FLU) decanoate for 8 months were assessed using intracranial microdialysis 1 month after final injection. Both HAL- and FLU-treated animals showed persisting plasma neuroleptic levels at time of sacrifice. Extracellular basal levels of homovanillic acid (HVA) in the CPu were significantly elevated in the FLU-treated animals, while basal levels of 3,4-dihydroxyphenylacetic acid (DOPAC) in the CPu were significantly elevated in the HAL-treated animals. Basal levels of DA and the serotonin metabolite, 5-hydroxyindoleacetic acid (5HIAA) in the CPu were not significantly different between groups. No significant between-group differences were found for basal levels of any of the analytes in the NA. Neuroleptic-treated animals showed an enhanced response to direct infusion through the dialysis probe of amphetamine (1 microM) and nomifensine (10 microM) in the CPu but not the NA. These results suggest that chronic neuroleptic treatment produces enhanced extracellular DA activity in nigrostriatal, but not mesolimbic DA pathways.

Differences between antipsychotic drugs in persistence of brain levels and behavioral effects

After a single dose of the butyrophenone neuroleptic haloperidol, behavioral effects and detectable drug levels in rat brain can last for several weeks. To determine if such persistence is a general property of neuroleptics, we compared drug levels and effects after IP administration of two butyrophenones (haloperidol and bromperidol), a high potency (fluphenazine) and a low potency (chlorpromazine) phenothiazine. Drug levels in brain tissue were measured by high pressure liquid chromatography and behavioral effects monitored as inhibition of apomorphine-induced stereotypy. Estimated near terminal elimination half-lives (t 1/2) from brain for acutely administered chlorpromazine (20 mg/kg) and fluphenazine (1 mg/kg) were 0.41 and 0.62 days, respectively, and neither drug was detectable after 4 days. Fluphenazine given daily for 5 days showed an only slightly slower elimination (t 1/2 = 1.1 days). In contrast, near-terminal elimination half-lives from brain for haloperidol and bromperidol (both at 1 mg/kg, IP) were much longer (6.6 and 5.8 days, respectively), and each was detectable for 21 days after dosing. Inhibition of apomorphine-induced stereotypy correlated highly (r = 0.95) with brain levels of haloperidol. For fluphenazine, given once or repeatedly, early inhibition was replaced within 1 week by supersensitivity to apomorphine which persisted for up to 3 weeks. These findings, indicating marked differences in clearance and recovery times after dosing with butyrophenones and phenothiazines, have clear implications for studies of the effects of neuroleptic drugs in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine blocking activity of clomipramine in patients with obsessive-compulsive disorder

While many data suggest that Obsessive-Compulsive Disorder (OCD) is an illness accompanied by dysregulation of the serotonergic system, interesting clinical evidence and animal studies also suggest possible dysregulation of the dopaminergic (DA) system. In order to determine whether clomipramine (CMI), an antiobsessional agent, is capable of altering DA function, we performed a neuroleptic radioreceptor assay (NRRA) on plasma samples from OCD patients before and after treatment in a double-blind, placebo controlled trial of CMI. CMI produced mild but significant DA D-2 receptor binding activity in an in vitro assay. The degree of dopamine binding activity did not correlate with clinical response to clomipramine. Because it has been suggested that another drug with antiobsessional efficacy, fluoxetine, may also have dopamine blocking properties, it may be speculated that antidopaminergic activity in combination with serotonergic effects is involved in antiobsessional activity of effective agents for some patients.

Noninvasive in vivo detection of a fluorinated neuroleptic in the human brain by 19F nuclear magnetic resonance spectroscopy

A fluorinated long-acting neuroleptic (fluphenazine decanoate) was detected in the human brain by fluorine nuclear magnetic resonance spectroscopy (MRS). The MRS system used had a 3 Tesla magnetic field, corresponding to a frequency of 118 MHz for the fluorine nucleus (Bruker Medspec 3 Tesla, 60-cm magnet bore width). The spectra were obtained with a surface coil having a 10-cm diameter, which was centered alternatively on the frontal lobe and basal ganglia, and on the occipital lobe. The impregnation and elimination kinetics of fluphenazine were monitored during three sessions (4 hours, 5 days, and 11 days after injection of the compound). This technique can be usefully applied to the in vivo study of the pharmacokinetics and site of action of psychiatric compounds in man.

Antagonism of presynaptic dopamine receptors by phenothiazine drug metabolites

Electrically evoked release of dopamine from the caudate nucleus is reduced by the dopamine receptor agonists, apomorphine and bromocriptine, and facilitated by neuroleptic drugs, which act as dopamine autoreceptor antagonists. The potencies of chlorpromazine, fluphenazine, levomepromazine and their hydroxy-metabolites in modulating electrically evoked release of dopamine were examined by superfusion of rabbit caudate nucleus slices pre-incubated with 3H-dopamine. O-Desmethyl levomepromazine, 3-hydroxy- and 7-hydroxy metabolites of chlorpromazine and levomepromazine facilitated electrically evoked release of 3H-dopamine, having potencies similar to that of the parent compounds. 7-Hydroxy fluphenazine was less active than fluphenazine in this system. These results indicate that phenolic metabolites of chlorpromazine and levomepromazine, but not of fluphenazine, may contribute to effects of the drugs mediated by presynaptic dopamine receptors.

Chronic neuroleptic treatment in rats produces persisting changes in GABAA and dopamine D-2, but not dopamine D-1 receptors

The effects of continuous treatment with haloperidol (HAL) or fluphenazine (FLU) for 10 months on dopamine and GABA receptors in the rat brain was examined using in vitro autoradiography. Rats treated with HAL, but not FLU, showed an increase in D-2 receptor binding in the caudate-putamen as revealed by [3H]spiperone. Labeling of D-1 receptors by [3H]SCH23390 revealed no changes in either drug-treated group. Both drug-treated groups, however, exhibited a significant increase in [3H]muscimol binding in substantia nigra, pars reticulata (SNR). These dopaminergic-GABAergic receptor alterations may be related to previously reported changes in oral movement activity seen in these neuroleptic-treated animals.

Striatal dopamine receptor occupancy during and following withdrawal from neuroleptic treatment: correlative evaluation by positron emission tomography and plasma prolactin levels

The percentage occupation of striatal dopamine D2 receptors has been evaluated in 25 patients using 76Br-bromospiperone positron emission tomography (PET) and prolactin plasma levels (PRL) during oral neuroleptic treatment (11 studies), 1-90 days following discontinuation of such treatment (16 studies), and 1-120 days after last intramuscular administration of depot neuroleptics (nine studies). The PET-estimated occupation was highly significantly correlated in a sigmoid-like fashion to the logarithm of the chlorpromazine-equivalent dose of oral neuroleptics (suggesting a strict dose-occupation relationship during oral neuroleptic treatment and supporting the D2-mediated hypothesis of neuroleptic action), while PRL was weakly related to daily dosage. Following withdrawal, return to normal receptor availability, as estimated by PET, occurred within 5-15 days (suggesting that protracted effects of neuroleptics after withdrawal are not due to sustained D2 receptor occupation), but PRL values fell even more rapidly. Efficient treatment with depot neuroleptics resulted in marked PET-estimated D2 receptor occupation, stable over the whole 4-week drug-administration interval, suggesting that longer intervals could be appropriate; PRL values bore no relationship to PET-estimated occupation, indicating variable intersubject tolerance to neuro-endocrine dopamine blockade. Overall, PET was much more sensitive than PRL to estimate striatal D2 receptor occupation in vivo.

Decreasing sensitivity to neuroleptic agents in developing rats; evidence for a pharmacodynamic factor

Developing rats are far more sensitive than adults to the behavioral effects of haloperidol. The present results support the hypothesis that this change may reflect age-related changes in brain responses such as alterations in drug-receptor or drug-effector mechanisms. Dose-response studies of catalepsy and ptosis were conducted in male Sprague-Dawley rats aged 30, 56, or 100 days. Resulting dose-effect curves were approximately parallel and showed rightward shifts with highly significant progressive increases of ED50. Similar developmental decreases in drug sensitivity (3-6x) were found following systemic (PO or IP) administration of haloperidol or the phenothiazine neuroleptic perphenazine, which differ markedly in structure, potency, distribution, and metabolism. Age-related decreases in drug sensitivity (3-4x) were also found using intracerebroventricular (ICV) administration of both agents in an attempt to bypass potential "pharmacokinetic" influences. Since the age-dependent decrease in sensitivity to both neuroleptics was found during the rising phase of drug action (1st hour) and ranked: PO greater than IP greater than ICV, some change in absorption and distribution of both drugs may occur in addition to the apparently important maturational decrease in target-organ sensitivity indicated by the responses to direct ICV injection and by the similarity of results obtained with dissimilar agents.

Neuroleptic drugs in the treatment of acute psychosis: how much do we really know?

The efficacy of neuroleptic antipsychotic drugs has been well demonstrated and neuroleptics are the standard treatment of acute psychosis. However, important aspects of neuroleptic treatment, including course of response, optimal doses, and mechanism of action, remain poorly studied or controversial. Placebo-controlled studies of the onset of the response of acute psychosis to neuroleptics are few and yield conflicting results. Studies of the relationship of doses and blood levels to the therapeutic effects of neuroleptics suggest that the optimal range of doses and levels is narrow and that commonly used doses are too high. Finally, studies of the mechanism of action of neuroleptics suggest that the dopamine hypothesis is based on unsupported assumptions concerning drug effects, drug distribution, and effective doses of drug. Alternative hypotheses, that the antipsychotic effects of the neuroleptics are mediated, at least in part, through alpha 1-adrenergic or serotonin 5-HT2 receptor antagonism, are reviewed. The evidence regarding these issues and controversies is discussed, and specific approaches to increase our understanding and enhance our use of the neuroleptics are suggested.