Search

The recent development of high throughput compound screening has allowed drug repurposing to emerge as an effective avenue for discovering novel treatments for cancer. FDA-approved antipsychotic drugs fluspirilene, penfluridol, and pimozide are clinically used for the treatment of psychotic disorders, primarily schizophrenia. These compounds, belong to diphenylbutylpiperidine class of antipsychotic drugs, are the potent inhibitors of dopamine D(2) receptor and calcium channel. A correlation has been found that patients treated for schizophrenia have lower incidences of certain types of cancer, such as respiratory, prostate, and bladder cancers. These compounds have also been shown to inhibit cancer proliferation in a variety of cancer cells, including melanoma, lung carcinoma, breast cancer, pancreatic cancer, glioma, and prostate cancer, among others. Antipsychotic drugs induce apoptosis and suppress metastasis in in vitro and in vivo models through mechanisms involving p53, STAT3, STAT5, protein phosphatase 2A, cholesterol homeostasis, integrins, autophagy, USP1, wnt/β-catenin signaling, and DNA repair. Additionally, pre-clinical evidence suggests that penfluridol and pimozide act synergistically with existing chemotherapeutic agents, such as dasatinib, temozolomide, and cisplatin. Some studies have also reported that the cytotoxic activity of the antipsychotics is selective for dividing cells. Based on this growing body of evidence and the availability and previous FDA-approval of the drugs, the compounds appear to be promising anti-cancer agents.

The persistent increase of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) infections negatively impacts Tuberculosis treatment outcomes. Host-directed therapies (HDT) pose an complementing strategy, particularly since Mtb is highly successful in evading host-defense by manipulating host-signaling pathways. Here, we screened a library containing autophagy-modulating compounds for their ability to inhibit intracellular Mtb-bacteria. Several active compounds were identified, including two drugs of the diphenylbutylpiperidine-class, Fluspirilene and Pimozide, commonly used as antipsychotics. Both molecules inhibited intracellular Mtb in pro- as well as anti-inflammatory primary human macrophages in a host-directed manner and synergized with conventional anti-bacterials. Importantly, these inhibitory effects extended to MDR-Mtb strains and the unrelated intracellular pathogen, Salmonella enterica serovar Typhimurium (Stm). Mechanistically Fluspirilene and Pimozide were shown to regulate autophagy and alter the lysosomal response, partly correlating with increased bacterial localization to autophago(lyso)somes. Pimozide’s and Fluspirilene’s efficacy was inhibited by antioxidants, suggesting involvement of the oxidative-stress response in Mtb growth control. Furthermore, Fluspirilene and especially Pimozide counteracted Mtb-induced STAT5 phosphorylation, thereby reducing Mtb phagosome-localized CISH that promotes phagosomal acidification. In conclusion, two approved antipsychotic drugs, Pimozide and Fluspirilene, constitute highly promising and rapidly translatable candidates for HDT against Mtb and Stm and act by modulating the autophagic/lysosomal response by multiple mechanisms.

The persistent increase of multidrug-resistant (MDR)Mycobacterium tuberculosis(Mtb) infections negatively impacts Tuberculosis (TB) treatment outcomes. Host-directed therapies (HDT) pose an complementing strategy, particularly sinceMtbis highly successful in evading host-defense by manipulating host-signaling pathways. Here, we screened a library containing autophagy-modulating compounds for their ability to inhibit intracellularMtb-bacteria. Several active compounds were identified, including two drugs of the diphenylbutylpiperidine-class, Fluspirilene and Pimozide, commonly used as antipsychotics. Both molecules inhibited intracellularMtbin pro- as well as anti-inflammatory primary human macrophages in a host-directed manner and synergized with conventional anti-bacterials. Importantly, these inhibitory effects extended to MDR-Mtbstrains and the unrelated intracellular pathogen,Salmonella entericaserovar Typhimurium (Stm). Mechanistically Fluspirilene and Pimozide were shown to regulate autophagy and alter the lysosomal response, partly correlating with increased bacterial localization to autophago(lyso)somes. Pimozide’s and Fluspirilene’s efficacy was inhibited by antioxidants, suggesting involvement of the oxidative-stress response inMtbgrowth control. Furthermore, Fluspirilene and especially Pimozide counteractedMtb-induced STAT5 phosphorylation, thereby reducingMtbphagosome-localized CISH that promotes phagosomal acidification.In conclusion, two approved antipsychotic drugs, Pimozide and Fluspirilene, constitute highly promising and rapidly translatable candidates for HDT againstMtbandStmand act by modulating the autophagic/lysosomal response by multiple mechanisms.

Penfluridol has robust antipsychotic efficacy and is a first-generation diphenylbutylpiperidine. Its effects last for several days after a single oral dose and it can be administered once a week to provide better compliance and symptom control. Recently; strong antitumour effects for penfluridol were discovered in various cancer cell lines; such as breast; pancreatic; glioblastoma; and lung cancer cells via several distinct mechanisms. Therefore; penfluridol has drawn much attention as a potentially novel anti-tumour agent. In addition; the anti-cancer effects of penfluridol have been demonstrated in vivo: results showed slight changes in the volume and weight of organs at doses tested in animals. This paper outlines the potential for penfluridol to be developed as a next-generation anticancer drug.

We studied the blocking action of neuroleptic drugs, haloperidol, pimozide, and fluspirilene, on three types of cloned low voltage-activated (T-type) Ca2+ channels, α1G, α1H, and α1I, functionally expressed in Xenopus oocytes. Fluspirilene and pimozide (members of the diphenylbutylpiperidine group) and haloperidol (belonging to butyrophenones) inhibited Ca2+ currents with different values of the Kd constant and maximum intensity of blocking. Effects of the neuroleptics were voltage-dependent and were accompanied by slowing-down of the kinetics of the currents. The mechanism of blocking is probably based on interaction between the neuroleptics and the channels in the activated and inactivated states. The difference in efficiency and specificity of blockade of various T-channel subtypes by neuroleptics should be considered when estimating the therapeutic significance of the tested pharmacological agents.

Pimozide is a conventional antipsychotic of the diphenylbutylpiperidine class that has been clinically used for over 30 years. The obvious side effect of this drug is weight gain. However, the mechanism of pimozide-induced weight gain is still unknown. In the present study, we identified pimozide as a novel fatty acid binding protein 4 (FABP4) inhibitor using molecular docking simulation as well as biochemical characterizations. BMS309403, a well-known FABP4 inhibitor, elevated the basal protein levels of PPARγ, therefore stimulating adipogenesis in adipocytes. The present study showed that the inhibitory effect of pimozide on FABP4 promoted adipocyte differentiation with the potency proportional to their propensities for weight gain. These effects in adipogenesis by pimozide may help to explain the weight gain that is frequently observed in patients treated with pimozide.

1. High voltage-activated calcium currents were recorded in nerve growth factor (NGF)-differentiated PC12 cells with the whole-cell patch clamp technique. After exposure to NGF for 3-10 days the PC12 cells developed neurone-like processes and calcium currents which were pharmacologically separable into L- and N-types (defined by sensitivity to nifedipine and omega-conotoxin GVIA respectively). 2. After blocking the L-type calcium channels with nifedipine (10 microM), omega-conotoxin GVIA blocked approximately 85% of the remaining calcium current with an IC50 of 3 nM and a Hill coefficient of 1. The block by conotoxin GVIA was irreversible on the time scale of these experiments. These results suggested that the majority of the nifedipine-insensitive calcium current was N-type. 3. Fluspirilene, a substituted diphenylbutylpiperidine with potent neuroleptic properties, reversibly inhibited the N-type component in a dose-dependent manner with an IC50 of 30 nM. The Hill coefficient of the block was 0.25. The fraction of current blocked was the same at all test potentials examined (-30 to +40 mV). 4. These data indicate that the neuroleptic properties of fluspirilene may be due, at least in part, to an inhibition of neuronal N-type calcium channels. This finding raises the possibility that modulation of N-type calcium channel activity by drugs derived from substituted diphenylbutylpiperidines may provide a novel way of altering neurotransmitter release and hence brain function.

The function of low voltage-activated T-type Ca2+ channels in ACTH-stimulated cortisol production by bovine adrenal zona fasciculata cells (AZF) was explored in patch clamp and secretion studies. Nearly all AZF cells expressed only a low voltage-activated T-type Ca2+ current (IT) that was blocked by the diphenylbutylpiperidine (DPBP) Ca2+ antagonists penfluridol and pimozide with IC50S of 0.3 and 0.5 microM, respectively. Dihydropyridine (DHP) Ca2+ antagonists, including nimodipine, nisoldipine, and felodipine, also blocked T-type Ca2+ current with IC50S ranging from 3.5-8.8 microM. Inhibition of IT by DPBP and DHP antagonists was voltage and use dependent. ACTH (1 nM) stimulated large (> 50-fold) increases in cortisol production by AZF cells, which were inhibited by Ca2+ antagonists at concentrations similar to those which blocked IT. Inhibition of cortisol production by Ca2+ antagonists was specific; ACTH-induced insulin-like growth factor-I production by AZF cells was not affected by DPBP antagonists. The L channel-specific DHP Ca2+ agonist (-)Bay K 8644 did not enhance basal or ACTH-stimulated cortisol synthesis. These results demonstrate that functional T-rather than L-type Ca2+ channels are required for ACTH-stimulated cortisol synthesis. They also suggest that these low voltage-activated channels, acting as the primary pathway for Ca2+ entry into AZF cells, couple ACTH-stimulated membrane depolarization to steroid hormone production.

The effect of verapamil, which belongs to the group of drugs collectively reffered to as ‘organic Ca 2+ channel blockers’, was investigated on the basal and stimulated release of the neurotransmitters dopamine and GABA in rat striatum synaptosomes. Verapamil inhibits the Na + -dependent release of GABA in response to depolarization with an IC 50 of 25 μM, whereas it is unable to modify the Na 2+ -independent, Ca 2+ -dependent fraction of GABA release induced by high K + depolarization. Verapamil does not modify the basal release of GABA but stimulates the basal release of dopamine in a dose-dependent manner (ED 50 5μM). This verapamil-induced outflow of dopamine is independent of Ca 2+ and occurs in the presence of tetrodotoxin, indicating that it is not mediated by voltage-sensitive Ca 2+ or Na + channels of the presynaptic membrane. Dopamine release induced by verapamil is cumulative with that induced by depolarizing agents (high K + or veratridine). As verapamil, pimozide, a neuroleptic of the diphenylbutylpiperidine type, increases the basal and stimulated release of dopamine. We conclude that the opposite effects of verapamil of GABA and dopamine release are due to differences in the releasable fractions of these 2 types of neurotransmitters. Besides, none of these effects are directly linked with the blockade of voltage-operated Ca 2+ channels of the presynaptic membrane.

The effects of diphenylbutylpiperidine (DPBP) antipsychotics on Ca2+ currents and prolactin (PRL) synthesis were studied in rat pituitary growth hormone (GH) cell lines (GH3 and GH4C1). In whole-cell patch-clamp experiments, DPBPs including fluspirilene, penfluridol, and pimozide at concentrations ranging from 0.25 to 5 microM each blocked current through low threshold T-type as well as high threshold L-type channels. Each of the drugs preferentially blocked T-type current, and complete inhibition was observed at concentrations as low as 1 microM. Inhibition of L-type channels by DPBPS was enhanced at depolarized holding potentials and promoted by prolonged channel activation. At concentrations similar to those which blocked Ca2+ currents, each of the three DPBPs markedly reduced basal PRL production by GH cells. PRL synthesis stimulated by the dihydropyridine Ca2+ agonist R5417 or thyrotropin releasing hormone (TRH) was also inhibited. The inhibitory effects of the DPBPs were observed at the level of gene transcription. Penfluridol and fluspirilene inhibited basal, Ca2(+)- and TRH-stimulated expression of a fusion gene construct containing the 5'-flanking sequence of the rat PRL gene linked to the luciferase gene. The effect was concentration-dependent with the IC50 values for both drugs of less than 1 microM. Nimodipine also reduced basal, R5417, and TRH-stimulated expression of the reporter gene construct. Similar results were obtained with a reporter gene construct containing the 5'-flanking sequence of the rat GH gene. The GH luciferase construct was only slightly responsive to R5417 and TRH; however, these responses were reduced by fluspirilene and nimodipine at concentrations of less than 1 microM. These studies demonstrate that the DPBP antipsychotics block T- as well as L-type Ca2+ channels in GH cells and inhibit PRL production at the level of transcription. They also indicate that functioning Ca2+ channels are necessary for TRH-stimulated PRL gene transcription.

Three structural classes of commonly used amiloride analogs, molecules derivatized at the terminal guanidino-nitrogen, the five-position pyrazinoyl-nitrogen, or di-substituted at both of these positions, inhibit binding of the L-type Ca2+ channel modulators diltiazem, gallopamil, and nitrendipine to porcine cardiac sarcolemmal membrane vesicles. The rank order of inhibitory potencies among the various derivatives tested is well defined with amiloride being the least potent. Saturation binding studies indicate that inhibition of ligand binding results primarily from effects on Kd. Ligand dissociation measurements suggest that amiloride derivatives do not associate directly at any of the known sites in the Ca2+ entry blocker receptor complex. In addition, these compounds do not compete at the "Ca2+ coordination site" within the channel. However, studies with inorganic and substituted diphenylbutylpiperidine Ca2+ entry blockers reveal that amiloride analogs interact at a site on the channel where metal ions bind and occlude the pore. Photolysis experiments performed with amiloride photoaffinity reagents confirm that a specific interaction occurs between such probes and the channel protein. Upon photolysis, these agents produce concentration- and time-dependent irreversible inactivation of Ca2+ entry blocker binding activities, which can be protected against by either verapamil or diltiazem. 45Ca2+ flux and voltage-clamp experiments performed with GH3 anterior pituitary cells demonstrate that amiloride-like compounds inhibit L-type Ca2+ channels directly. Moreover, these compounds block contraction of isolated vascular tissue in pharmacological assays. Electrophysiological experiments indicate that they also inhibit T-type Ca2+ channels in GH3 cells. Taken together, these results demonstrate unequivocally that amiloride analogs display significant Ca2+ entry blocker activity in both ligand binding and functional assays. This property, therefore, can seriously complicate the interpretation of many in vitro and in vivo studies where amiloride analogs are used to elicit inhibition of other transport systems (e.g. Na-Ca and Na-H exchange).

The effects of local anesthetics were examined on a family of transiently expressed neuronal calcium channels. Fomocaine, a local anesthetic containing a morpholine ring, preferentially blocked alpha1E channels (Ki = 100 microM), and had a lower affinity (3- to 15-fold) for alpha1A, alpha1B, and alpha1C channels. Block was incompletely reversible, followed 1:1 kinetics, and did not affect steady-state inactivation properties. Fomocaine block was sensitive to the concentration of permeant ion and enhanced in the presence of external pore blockers, suggesting a site of action in the conducting pathway. Flecainide, which carries a piperidine ring, and the diphenylbutylpiperidine antipsychotic, penfluridol, caused qualitatively similar block, suggesting that morpholine rings are compatible with the piperidine receptor site. In contrast, procaine, which contains an alkyl chain, caused reversible low affinity block of the different calcium channels (Kd values between 2 and 5 mM) and was least effective on alpha1E and did not compete with fomocaine, suggesting that local anesthetics interact with at least two distinct receptor sites. Compared to coexpression with the Ca channel beta1b subunit, block at the piperidine receptor site was significantly weakened with the beta2a subunit suggesting that the nature of the beta subunit contributes to drug binding. Amino acid changes in the cytoplasmic linker between domains I and II resulted in decreased fomocaine and penfluridol blocking affinity. Furthermore, the blocking affinity observed with alpha1B, was conferred on alpha1A by substitution of the domain I-II linker of alpha1B into alpha1A. Taken together, the data suggest that beta subunit binding and the domain I- II linker contribute to the piperidine receptor site on neuronal calcium channels.

A novel series of diphenylbutylpiperidine derivatives in which a benzo-five or six membered heterocycle was linked at the 4-position of the piperidine moiety were designed and synthesized. Structure–activity relationship (SAR) studies of these compounds indicated that some molecules show promising autophagy inducing activity. Replacement of the fluorine atom by a CF3 group on the diphenyl part resulted in significant enhancement of the autophagy inducing effect. In the addition, a group of diphenylpentyl nitriles also showed similar bioactivities.

[3H]Fluspirilene, a neuroleptic molecule of the diphenylbutylpiperidine series, binds to skeletal muscle transverse tubule membranes with a high affinity corresponding to a Kd of 0.11 +/- 0.04 nM, A 1:1 stoichiometry was found between [3H]fluspirilene binding and the binding of (-)-[3H]desmethoxyverapamil [(-)[3H]D888], one of the most potent Ca2+ channel inhibitors. Ca2+ channel inhibitors such as D888, verapamil, gallopamil, bepridil, or diltiazem antagonize [3H]fluspirilene binding besides antagonizing (-)[3H]-D888 binding. Neuroleptics, especially those of the diphenylbutylpiperidine family, also antagonize both (-)[3H]D888 binding and [3H]fluspirilene binding. There is an excellent correlation between affinities found from [3H]fluspirilene binding experiments and those found from (-)[3H]D888 binding experiments. Analysis of the properties of these cross-inhibitions indicates that [3H]fluspirilene binds to a site that is not identical to that for phenylalkylamine derivatives (gallopamil, verapamil, diltiazem, and bepridil). Voltage-clamp experiments have shown that fluspirilene is an efficient inhibitor of the voltage dependent Ca2+ channel, achieving a half-maximal effect near 0.1-0.2 nM and nearly complete blockade at 1 nM. Fluspirilene blockade has little voltage dependence.

Twenty-two hospitalized schizophrenic patients, participating in a large-scale phase II double-blind dose-effect study (30, 60, and 120 mg weekly) of penfluridol, a new diphenylbutylpiperidine neuroleptic, were maintained on a regular dosage regimen for 13 wk. Several blood samples were taken during the last dosage interval. Results show that the peak concentration develops within 12 hr after the last dose. A rapid decline, probably due to tissue re-equilibration, then occurs and is followed by a much slower falloff. Detectable concentrations 168 hr after administration are consistent with the long duration of action of penfluridol. Statistically significant differences between doses were found in the analysis of variance of plasma concentrations at all sampling times and in mean steady-state plasm concentrations. Wide differences in plasma concentrations were noted in patients receiving the same absolute dose, but a good relationship was defined between mean steady-state concentration and the dose expressed as mg per either kg of body weight or square meter of body surface area.

Fluspirilene binds with high affinity to a single class of sites in purified porcine cardiac sarcolemmal membrane vesicles at a Kd of 0.6 nM and a Bmax that is in approximately 1:1 stoichiometry with other Ca2+ entry blocker receptors. Fluspirilene binding is modulated by various classes of L-type Ca2+ channel effectors. Metal ion channel inhibitors (e.g. Cd2+) stimulate binding primarily by increasing ligand affinity, whereas channel substrates (e.g. Ca2+) inhibit binding. Dihydropyridine, aralkylamine, and benzothiazepine Ca2+ entry blockers partially inhibit binding with Ki values equivalent to their respective Kd values, indicating close coupling between binding sites for the former agents and the diphenylbutylpiperidine site. All of these agents function as mixed inhibitors and affect both Kd and Bmax of fluspirilene binding. Only other substituted diphenylbutylpiperidines (e.g. pimozide) inhibit binding competitively. Diphenylbutylpiperidines, on the other hand, block nitrendipine, D-600, and diltiazem binding through a noncompetitive mechanism with Ki values much reduced from their measured Kd values, suggesting that coupling between the diphenylbutylpiperidine site and receptors for diverse Ca2+ entry blockers is more indirect. In addition, high affinity sites have been detected for fluspirilene in bovine aortic sarcolemmal vesicles, rat brain synaptic membranes, and GH3 rat anterior pituitary cell plasma membranes. Fluspirilene also effectively blocks Ca2+ flux through L-type Ca2+ channels in GH3 cells. Together, these results suggest that fluspirilene binds with high affinity to a unique fourth site in the Ca2+ entry blocker receptor complex and that substituted diphenylbutylpiperidines represent a new structural class of potent L-type Ca2+ channel inhibitors.

We evaluated the effect of several classes of calmodulin inhibitors on the activity of calmodulin prepared from C6 astrocytoma cells and studied the activity of these drugs as inhibitors of the growth of C6 cells in tissue culture. There was a good correlation between the activity of the drugs as inhibitors of calmodulin and their activity as inhibitors of cell growth. The most potent compounds were calmidazolium and melittin as compared to the phenothiazines, trifluoperazine, chlorpromazine, chlorpromazine-sulfoxide or the diphenylbutylpiperidine, pimozide. The mechanism by which the inhibition of calmodulin leads to the death of cells could not be attributed entirely to inhibition of the calmodulin-sensitive cyclic nucleotide phosphodiesterase. Calmodulin is a heat stable, calcium-binding protein involved in numerous biological processes. Recent evidence indicates that calcium and calmodulin may be important for cellular proliferation. For example, this protein changes in concentration during the cell cycle; is involved in the disassembly of the mitotic apparatus; is increased in concentration in rapidly growing hepatomas and in transformed fibroblasts. Weiss and co-workers demonstrated that phenothiazines and structurally similar drugs are capable of binding to and inhibiting the activity of calmodulin. It has been recently observed that certain drugs that inhibit the activity of calmodulin also inhibit the growth of malignant cells in vitro and in vivo. In these studies, however, there was no direct correlation of the effect of the drugs on the calmodulin from the cell type under investigation with cytotoxicity. To learn more about the relationship between a drug's ability to inhibit calmodulin and its antiproliferative activity, we correlated the effect of drugs on the activity of calmodulin prepared from the C6 astrocytoma cell line with their effect on cellular proliferation. Since many inhibitors of calmodulin readily cross the blood-brain barrier and since no acceptable treatment for malignancies of the central nervous system exist, we chose this cell line as a model for elucidating the potential antineoplastic effects of calmodulin inhibitors.

Antischizophrenic neuroleptic drugs of the diphenylbutylpiperidine class, which includes pimozide, fluspirilene, penfluridol, and clopimozide, inhibit [3H]nitrendipine binding with IC50 values of 13-30 nM. This inhibition involves receptors for the verapamil/prenylamine class of calcium channel antagonists. These diphenylbutylpiperidines also inhibit potassium-induced calcium-dependent contractions of rat vas deferens at concentrations of 40-350 nM. Other phenothiazine and butyrophenone neuroleptics lack such potent calcium-antagonist actions. Diphenylbutylpiperidines also differ from other neuroleptics in their ability to relieve negative symptoms of schizophrenia, such as emotional withdrawal, as well as the positive symptoms which respond to all neuroleptics. We suggest that these unique antischizophrenic actions are related to a blockade by diphenylbutylpiperidines of voltage-operated calcium channels.

Dihydropyridines are potent agents on [3H]nitrendipine binding sites in heart and brain membranes. Like the phenylalkylamines, they are slightly more active on heart than on brain [3H]nitrendipine binding sites. On the other hand, the diphenylalkylamines, the diphenylpiperazines and the antischizophrenic drugs of the diphenylbutylpiperidine type are more potent on brain [3H]nitrendipine binding sites. The findings suggest tissue heterogeneity of [3H]nitrendipine binding sites and the possible development of diphenylbutylpiperidine-diphenylbutylpiperazine analogues that could selectively act on brain calcium channel antagonist binding sites.

Neuroleptic molecules of the diphenylbutylpiperidine series (DPBP), such as fluspirilene, penfluridol, pimozide and clopimozide, antagonize binding of (−)[ 3 H]desmethoxyverapamil ((−)[ 3 H]D888) and (+)[ 3 H]PN 200-110 to rabbit brain, heart and smooth muscle membranes. The diphenylbutylpiperidine binding site in all these tissues is distinct but is allosterically related to the 1,4-dihydropyridine binding site and to the binding site. High and low affinity binding sites for (−)D888 were identified. (−)[ 3 H]D888 binding at both types of sites was inhibited following the saturation of a single type of diphenylbutylpiperidine binding site. Half-maximal inhibition (K 0.5 ) of brain, heart and smooth muscle membranes binding by different diphenylbutylpiperidines was in the range of 10–100 nM. These K 0.5 values were one to two orders of magnitude higher than those found for the high affinity diphenylbutylpiperidine receptor in skeletal muscle membranes. The K 0.5 values found in binding experiments in smooth muscle were similar to the (IC 50 ) values for half-maximal inhibition by diphenylbutylpiperidine of voltage-dependent 45 Ca 2+ influx through the slow Ca 2+ channel.

Forty patients have been treated for two months with fluspirilene, a new injectable diphenylbutylpiperidine administered intramuscularly once per week. Chronic cases improved satisfactorily and acute cases did rather better, particularly in relation to delusions. When the average dose was low ( 5.4 mg) extra-pyramidal effects were uncommon, but if 12 mg was given, more side-effects were encountered. Two patients on fluspirilene 4 mg weekly had dystonic reactions. If marked hypertension was present, the systolic pressure fell by about 60 mm Hg.

A procedure is described for TLC detection and differentiation of the butyrophenone-diphenylbutylpiperidine group and phenothiazine derivatives at the microgram level. A two-dimensional TLC method to separate butyrophenone and diphenylbutylpiperidine compounds is reported. A variety of possible detection reagents were examined. The solvent systems and spray reagents described should be useful for the identification of these drugs in various dosage forms.

Spectral sensitivity functions and the transient decrease of sensitivity to short wavelengths after the offset of yellow light (Mollon and Polden, 1977) were measured by increment threshold techniques in patients suffering from acquired colour vision deficiencies, caused either by drugs or by hereditary retinal degenerations. Compared with normal observers (n =11) Diphenylbutylpiperidine (IMAP®, 1.5mg/week over 18 months) reversibly decreases the blue cone mechanism’s sensitivity by a factor of 50 (during yellow adaptation of 1400 Td) and also abolishes transient tritanopia. Except for a mild deutan defect in the FM 100-hue test all ophthalmological investigations yielded normal results. Similar changes in the course of transient tritanopia were observed after long-term treatment with Carbamazepine (400mg/day) and Phenacetin (100mg/day). The three-peaked spectral sensitivity function, obtained with monochromatic test flashes of 400 ms duration in presence of white adapting lights (15.360 Td) was surprisingly little affected. A control group of patients with ophthalmoscopically evident hereditary macular degenerations showed comparably small changes in the course of transient tritanopia and in their spectral sensitivity function (Zrenner, Nowicki and Adamc- zyk, 1986).

Intracerebroventricular injection into rats of mast-cell degranulating peptide (MCD), dendrotoxin I (DTX I ) and 4-aminopyridine (4-AP), three blockers of a subclass of K + channels, elicited epileptiform wave bursts and convulsions. Three different types of L-type Ca 2+ channel inhibitors (+)PN 200-110, a 1,4-dihydropyridine, (−)D 888 , a phenylalkylamine, and fluspirilene, a diphenylbutylpiperidine, were potent blockers of the convulsant-induced hyperexcitatory effects when they were administered preventively. D-AP 5 , a N-methyl-D-aspartate antagonist, was active on the 4-AP-induced seizures but was without effect on the MCD- and dendrotoxin-induced seizures.

The interaction of putative Ca2+ channels of Drosophila head membranes with molecules of the phenylalkylamine series was studied from binding experiments using (-)-[3H]D888 and (+/-)-[3H]verapamil. These ligands recognize a single class (Kd = 0.1-0.4 nM; Bmax = 1600-1800 fmol/mg of protein) of very high affinity binding sites. The most potent molecule in the phenylalkylamine series was (-)-verapamil with a Kd value as exceptionally low as 4.7 pM. Molecules in the benzothiazepine and diphenylbutylpiperidine series of Ca2+ channel blockers as well as bepridil inhibited (-)-[3H]D888 binding in a competitive way with Kd values between 12 and 190 nM, suggesting a close correlation, as in the mammalian system, between these receptor sites and those recognizing phenylalkylamines. A tritiated (arylazido)phenylalkylamine with high affinity for the Drosophila head membranes, phenylalkylamine receptor Kd = 0.24 nM), was used in photoaffinity experiments. A protein of Mr 135,000 +/- 5,000 was specifically labeled after ultraviolet irradiation.