Interactions between dipfluzine-based complexes and cytochrome P450 enzymes: Information on salt, cocrystal, and salt cocrystal complexes.

In the new drugs, greater than 90 % of active pharmaceutical ingredients (APIs) or marketed drugs have poor solubility and bioavailability, which restrict the development of pharmaceutical preparations. The use of crystalline molecular complexes (CMCs) involving API and biocompatible precursors to improve solubility has become a shortcut for new drug development. Most of the new drugs registered in CMC form are from postmarketing drugs, and the interaction between these drugs and cytochrome P-450 (CYP) enzymes is well documented. However, it is unclear whether the interactions between CMCs of postmarketing drugs and CYP enzymes should be re-evaluated. To clarify this problem, three dipfluzine (Dip)-based CMCs, including Dip-benzoic acid (BA) cocrystal, Dip-2-hydroxybenzoate (2HB) salt and Dip-4-hydroxybenzoate (4HB) salt-cocrystal, were chosen to investigate the interaction with CYP enzymes. Metabolites of Dip-based CMCs and cocktail probe drugs were measured via LC-MS/MS in the incubation reaction system comprising recombinant CYP enzymes (rCYPs) and human liver microsomes. Dip-based CMCs not only alter Dip-mediated inhibition or activation of CYP enzymes but also change the degree to which rCYPs are involved in Dip metabolism. Specifically, the inhibitory effects of Dip and Dip-HCl were increased compared with Dip-BA and Dip-2HB for CYP1A2; Dip-BA, Dip-2HB and Dip-4HB for CYP3A4; and Dip-BA for CYP2E1. The inhibitory effects of Dip and Dip-HCl were reduced compared with Dip-2HB and Dip-4HB for CYP2C19 and Dip-4HB for CYP2E1. The effects of the alterations of Dip CMCs on the interaction between Dip and CYP enzymes are not attributed to a simple superposition of Dip and the respective precursor and may be due to the presence of interaction forces between Dip and precursor molecules. These results are the first to provide preliminary experimental evidence that CMCs change the interaction between API and CYP enzymes. Moreover, these results further suggest the importance of re-evaluating interactions with CYP enzymes when CMC strategies are used to design new drugs and even for CMCs of postmarketing drugs with known metabolic characteristics.

Vasodilation activity of dipfluzine metabolites in isolated rat basilar arteries and their underlying mechanisms.

Identifying the metabolites of a drug has become an indispensable task in the development of new drugs. Dipfluzine (Dip) is a promising candidate for the treatment of cerebral vascular diseases and has 5 metabolites (M1∼M5) in rat urine and liver microsomes, but their biological activity is still unknown. Because selective cerebral vasodilation is a main role of Dip, we investigated the vasodilation of Dip and its 5 metabolites in isolated Sprague-Dawley (SD) male rat basilar arteries preconstricted with high-K+ or 5-HT. The results showed that only M1 possessed concentration-dependent inhibitory activity on the vasoconstriction of arteries with or without the endothelium, and M1 has a more potent vasodilatory effect than Dip on both contraction models. Like Dip, the vasodilatory mechanisms of M1 may be not only related to receptor-operated and voltage-dependent calcium ion channels of smooth muscle cells but also to the release of NO and EDHF from endothelial cells and the opening of Ca2+-activated K+ channels and ATP-sensitive potassium ion channels. Unlike Dip, the vasodilation mechanism of M1 is also related to the opening of voltage-sensitive K+ channel. Together with more selectivity to non-VDCC than Dip, this may partially explain why M1 has stronger vasodilatory effects than Dip. The mechanisms of vasodilation of Dip and M1 may result from the combined action of these or other factors, especially blocking non-endothelium dependent non-VDCC and endothelium dependent IKCa channels. These results point to the possibility that M1 provides synergism for the clinical use of Dip, which may inform the synthesis of new drugs.

Identification of the rat liver cytochrome P450 enzymes involved in the metabolism of the calcium channel blocker dipfluzine hydrochloride.

This study aimed to identify the specific cytochrome P450 (CYP450) enzymes involved in the metabolism of dipfluzine hydrochloride using the combination of a chemical inhibition study, a correlation analysis and a panel of recombinant rat CYP450 enzymes. The incubation of Dip with rat liver microsomes yielded four metabolites, which were identified by liquid chromatography-coupled tandem mass spectrometry (LC/MS/MS). The results from the assays involving eight selective inhibitors indicated that CYP3A and CYP2A1 contributed most to the metabolism of Dip, followed by CYP2C11, CYP2E1 and CYP1A2; however, CYP2B1, CYP2C6 and CYP2D1 did not contribute to the formation of the metabolites. The results of the correlation analysis and the assays involving the recombinant CYP450 enzymes further confirmed the above results and concluded that CYP3A2 contributed more than CYP3A1. The results will be valuable in understanding drug-drug interactions when Dip is coadministered with other drugs.

Pharmacokinetic evaluation of dipfluzine and its three metabolites in rat plasma using liquid chromatography-mass spectrometry.

A validated LC-MS/MS method to determine the content of dipfluzine (Dip) and its three metabolites (M1, M2, and M5) simultaneously within rat plasma samples was developed. After a single liquid-liquid extraction, the assay was performed by using a C18 column and positive electrospray ionisation mode (ESI) in the multiple reaction monitoring (MRM) mode with transitions of m/z 417.3→167.3, 251.2→165.2, 199.1→121.3, and 183.2→105.1 for Dip, M1, M2, and M5, respectively. Sulfamethoxazole (SMZ) was used as internal standard (IS). The method was linear ranged from 0.5-518, 0.5-524, 1.0-1036, and 0.5-514 ng/ml for Dip, M1, M2, and M5, respectively and all correlation coefficients were greater than 0.9919. The intra- and inter-day precision values obtained were less than 11.5% and the accuracy was between -3.2 and 9.7% for each analyte. The extraction recoveries of their three concentrations for Dip and its three metabolites were all higher than 71.9%. The technique was successfully applied to a pharmacokinetic study of Dip and its metabolites after a single oral administration of Dip (20 mg/kg) to rats. The results indicated that the metabolite formation was rapid and generated M5 as the predominant metabolite, followed by M1 and M2. The maximum plasma concentrations (Cmax) were 59±7, 37±4, 3±0.2, and 55±5 ng/ml; the time to maximum plasma concentration (Tmax) were 65±12, 95±12, 190±25, and 90±0 min and the areas under the concentration-time curves (AUC0→∞) were 17573±704, 8328±355, 5602±753, and 16101±429 ng min/ml for Dip, M1, M2, and M5, respectively. These results suggested that Dip was extensively metabolized and rapidly absorbed. The half-life (t1/2) of Dip, M1, M2, and M5 were 329±15, 767±75, 2364±434, and 378±36 min, respectively, which indicated that Dip and M5 were eliminated quickly. M2 reached its Tmax later and exhibited a longer t1/2 than the other metabolites, which indicated that there might be some type of flip-flop mechanism at work in the pharmacokinetics of M2.

Preparation, characterization, and evaluation of dipfluzine-benzoic acid co-crystals with improved physicochemical properties.

PURPOSE: To prepare and characterize the co-crystal of dipfluzine and benzoic acid. To investigate the feasibility of the co-crystal for improving solubility and a faster dissolution rate in vitro and evaluate the bioavailability and tissue distribution of co-crystal in vivo. METHODS: A novel dipfluzine-benzoic acid co-crystal prepared using the solvent-assisted co-grinding and the solvent ultrasonic methods were identified and characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), as well as Raman, solid-state nuclear magnetic resonance (ssNMR), and terahertz (THz) spectroscopy. Pharmacokinetics and tissue distribution were tested in vivo using murine models. Statistics analysis for dissolution data of co-crystal in vitro and animal experiment data in vivo were evaluated using t-test. RESULTS: Results of PXRD and DSC identified the dipfluzine-benzoic acid co-crystals were formed with a molar ratio of 1:2. The IR, Raman, and ssNMR spectra verified the formation of O-H · · · O and O-H · · · F hydrogen bonds. The complex constant, K, was evaluated to be 10(9) orders of magnitude with Δ r G < 0. The co-crystal solubility, the rate of drug dissolution and the relative bioavailability were approximately 500 times, five times and double that of dipfluzine, respectively. Increased solubility of co-crystal did not reduce distribution in the brain; the mean concentrations in the brain increased, but the differences had no statistic significance (p > 0.05). CONCLUSIONS: The co-crystal of dipfluzine-benzoic acid improved the physicochemical properties of dipfluzine, such as solubility and dissolution rate. Furthermore, the increased relative bioavailability of co-crystal indicated the potential use in further clinical study.

Use of the co-grinding method to enhance the dissolution behavior of a poorly water-soluble drug: generation of solvent-free drug-polymer solid dispersions.

The solid dispersion (SD) technique is the most effective method for improving the dissolution rate of poorly water-soluble drugs. In the present work, SDs of the Ca2+ channel blocker dipfluzine (DF) with polyvinylpyrrolidone K30 (PVP) and poloxamer 188 (PLXM) were prepared by the powder solid co-grinding method under a solvent-free condition. The properties of all SDs and physical mixtures were investigated by X-ray diffraction, Fourier-transform infrared, differential scanning calorimetry, scanning electron microscopy, dissolution test, and particles size determination. Eutectic compounds were produced between the DF and PLXM matrix during the co-grinding process, whereas glass suspension formed in the SDs with PVP carrier. Hydrogen bond formation was not observed between DF and carriers and DF was microcrystalline state in the PVP and PLXM matrices. The solubility of DF in different concentration of carriers at 25, 31, and 37°C was investigated; the values obtained were used to calculate the thermodynamic parameters of interaction between DF and carriers. The Gibbs free energy (ΔrGθ) values were negative, indicating the spontaneous nature of dispersing DF into the carriers. Moreover, entropy is the drive force when DF disperses into the matrix of PVP, while, enthalpy-driven dispersing encounters in the PLXM carrier. All the SDs of DF/carriers showed a considerably higher dissolution rate than pure DF and the corresponding physical mixtures. The cumulative dissolution rate at 10 min of the SD with a 1 : 3 DF/carrier ratio increased 5.1-fold for PVP and 5.5-fold for PLXM.

Simultaneous determination of a novel diphenylpiperazine calcium channel blocker and its four metabolites in rat liver microsomes by liquid chromatography tandem mass spectrometry.

Dipfluzine hydrochloride (Dip), a novel diphenylpiperazine calcium channel blocker, has revealed the characteristics of a promising candidate for the treatment of cerebral vascular diseases in preclinical studies. Our research identified and quantified Dip and its 4 metabolites (M1, M2, M4 and M5) in rat liver microsomes by liquid chromatography tandem mass spectrometry. The results showed that Dip was firstly metabolized to M1 and M5 by 1- and 4-dealkylation from a piperazine nitrogen, and then the latter was subsequently metabolized to M2 and M4. The concentrations of Dip, M1, M2 and M5 were 557.3 ± 26.3, 854.3 ± 46.0, 2796.7± 126.9, 2473.3 ± 82.6 and 4.0 ± 0.4, 2.4 ± 0.1, 318.2 ± 8.7 and 27.4 ± 1.5 ng/ml in male and female rats, respectively. M4 (404.2 ± 22.2 ng/ml) was detected only in males not in females, suggesting that there is gender difference in the metabolism of Dip.

[Synthesis and spectral characteristic of pharmaceutical dipfluzine hydrochloride-benzoic acid co-crystal].

Pharmaceutical co-crystals can improve the chemical and physical properties of active pharmaceutical ingredient (API), which is new idea and expected to provide new stable structures. Pharmaceutical co-crystals have the potential to be much more useful in pharmaceutical products than salts, solvates or hydrates, polymorphs and stoichiometric solvates (pseudo-polymorphs). In our study, dipfluzine hydrochloride-benzoic acid co-crystal was synthesized by solid co-grinding. The samples were subjected to IR, DSC, XRD, Raman and THz spectral analysis. The results indicated that dipfluzine hydrochloride-benzoic acid complex was new phase compared with the single API and CCF. THz-TDS characterization indicated that hydrogen bond formed between API and CCF, which confirmed the formation of co-crystal.

Acute toxicity and toxicokinetics of dipfluzine hydrochloride, a novel calcium channel blocker.

Dipfluzine hydrochloride, diphenylpiperazine calcium channel blocker, is a promising candidate to treat ischemic stroke. The purpose of the study is to evaluate the acute toxicity and toxicokinetics of dipfluzine hydrochloride after single intravenous doses in rats. Acute toxicity study was performed in rats at doses of 5, 6, 10, 15, 25, 30, 35, and 40mg/kg. Concentrations of dipfluzine in plasma and tissues were determined with a reverse-phase HPLC method after single doses of 5, 15 and 30mg/kg. The results demonstrated that no-observed-adverse-effect level (NOAEL), lowest-observed-adverse-effect level (LOAEL), maximal tolerance dose (MTD), and minimal lethal dose (MLD) were respectively 5, 6, 30, 35mg/kg for i.v. administration of dipfluzine hydrochloride. The toxicokinetic study revealed that the severity of toxicity was linear with the level of systemic exposure. The highest tissue exposure was detected in lung tissue and it may primarily contribute to the pulmonary congestion in dead rats. Longer elimination half-lives of dipfluzine in kidney, brain, liver, and pancreas imply a possible accumulation of dipfluzine in these tissues for long-term exposure. In addition, a temporary impairment in liver and heart was observed for clinical chemistry in 30mg/kg dose group. The findings will help to design further studies to characterize the repeat-dose toxicity of dipfluzine hydrochloride.

Mechanism of anti-apoptotic action of dipfluzine on neuronal damage of the rat hippocampal CA1 region subjected to transient forebrain ischemia.

AIM: To explore the relations between anti-apoptotic role of dipfluzine (DIP) and the death signaling transduction pathway initiated by CD95 molecules, and the transcription factor involved in the transcription regulation of CD95 molecules in the hippocampal CA1 region after transient forebrain ischemia. METHODS: The rat forebrain transient ischemia model was established through 15 min ischemia followed by 3 days reperfusion by using the four-vessel method. The rats were divided randomly into five groups: sham control group, ischemia/reperfusion (I/R) group, DIP treated groups (20, 40 and 80 mg x kg(-1) body weight, ig, separately). Western blotting and RT-PCR were performed to detect the expression changes of Fas, FasL, caspase 10 p20, caspase 8, I-kappaB-alpha, and p-I-kappaB-alpha molecules in protein and mRNA levels, separately, and immunohistochemistry for molecular localization of Fas and FasL in rat hippocampus. RESULTS: The expression of Fas, FasL, and caspase 10 p20 in protein and mRNA levels increased after I/R, which was inhibited significantly after treatment with 20 and 40 mg x kg(-1) of DIP (P < 0.01). In 80 mg x kg(-1) of DIP group, the expression of Fas and FasL protein was not significantly different from that of I/R group (P > 0.05). The expression of caspase 8 and I-kappaB-alpha showed no significant differences in all groups (P > 0.05), and no gene expression was observed for p-I-kappaB-alpha protein in the study. DIP significantly affected molecular distribution of Fas and FasL protein in CA1 subregion of hippocampus. CONCLUSION: DIP inhibits the death signaling transduction pathway initiated by CD95 molecules in rat hippocampal CA1 subregion, and NF-kappaB transcription factor may not be involved in the transcription regulation of CD95 molecules after transient forebrain ischemia.

[Metabolic pathways of dipfluzine in rats].

AIM: To investigate the metabolic pathways of dipfluzine in rats. METHODS: After an oral dose of dipfluzine (80 mg x kg(-1)) to rats, urine was collected for 12 h. The metabolites of dipfluzine in urine were chromatographed and identified by LC/DAD/MS methods. RESULTS: In the rat urine, there were 1-(4-fluorophenyl)-4-piperazinylbutanone and its glucuronide, 4-hydroxybenzophenone and its glucuronide, 4-fluoro-gamma-hydroxybenzenebutanoic acid and its glucuronide and sulfate, diphenylmethanol and its glucuronide, dipfluzine, and benzophenone. CONCLUSION: In rats, dipfluzine was mainly metabolized in the pathways of N-desalkylation at 1- and 4-positions of piperazine ring. Some of metabolites were further conjugated with glucuronic acid and/or sulfuric acid.

[Effects of dipfluzine on expressions of E-selectin, P-selectin, and ICAM-1 in brain ischemia-reperfusion rats].

AIM: To evaluate the effects of dipfluzine on the expressions of E-selectin, P-selectin, and ICAM-1 and the infiltration of polymorphonuclear leukocytes in brain ischemia-reperfusion rats. METHODS: The model of focal cerebral ischemia was established with the Zea-Longa occluding suture. Dipfluzine (0.25, 0.5 and 1 mg x kg(-1)), flunarizine 0.5 mg x kg(-1) and solvent were injected separately into lingual vein at 30 min after ischemia. The occluding suture was slowly taken away to cause reperfusion at 1 h after ischemia. Rats were decapitated under anesthesia at 24 h after ischemia-reperfusion and brains were immediately removed to do the following procedures. Effects of dipfluzine on morphology of the brain tissue were observed through hematoxylin-eosin (HE) staining. By immunohistochemistry and flow cytometry technique and biochemical method, effects of dipfluzine on P-selectin, E-selectin, ICAM-1 and myeloperoxidase (MPO) were observed. RESULTS: Dipfluzine could relieve pathological damages in the brain tissue after ischemia-reperfusion, and reduce the expressions of E-selectin, P-selectin and ICAM-1 and activities of MPO in dose-dependent manner. CONCLUSION: Dipfluzine depresses the expressions of P-selectin, E-selectin, and ICAM-1, which are correlated with their effects on the activities of MPO, suggesting that dipfluzine has anti-inflammation effect in certain extent and could protect brain tissue from ischemia-reperfusion injury.

[Effect of dipfluzine on acute ischemic brain edema in gerbils].

OBJECTIVE: To examine the effect of dipfluzine (Dip), a novel calcium channel blocker first developed in China, on acute ischemic brain edema. METHODS: One hundred and thirty gerbils, 65 males and 65 females, weighing 68 +/- 10 g, were used. Eighty gerbils randomly divided into four groups of 20 animals: sham operation group, Dip 25 mg/kg group, and Dip 50 mg/kg group. All of the 120 gerbils were injected with solution or Dip at different concentrations intraperitoneally. The skin of neck was incised one hour after injection. Except in the sham operation group, bilateral carotid artery ligation (BCAL) was performed in the other 70 gerbils to cause brain edema. Another 10 gerbils were used as normal controls without undergoing injection and operation. One hour after the operation, all of the animals were killed and the whole brain tissue was taken to detect the water and Na(+) and K(+) contents. The brain tissues of other 50 gerbils were used to produce homogenate to determine the Na(+), K(+)-ATPase activity. RESULTS: The water and Na(+) contents in hippocampus of model control group were 77.4% and 279 +/- 22 micro mol/g dry tissue respectively, significantly higher than those in sham operation group (74.8% and 220 +/- 22 micro mol/g dry tissue). The K(+) content in the hippocampus of the model control group was 381 +/- 28 micro mol/g dry tissue respectively, significantly lower than that in the sham operation group (430 +/- 30 micro mol/g dry tissue). The Na(+), K(+)-ATPase activity in the plasmalemma of brain cells in model control group was 179 +/- 62 micro mol pi/mg protein/min, significantly lower than that in sham operation group (1006 +/- 130 micro mol pi/mg protein/min, P < 0.01). The water contents of hippocampus in Dip 25 mg/kg group and Dip 50 mg/kg group were 75.4 +/- 0.5% and 74.8 +/- 0.9% respectively, significantly lower than that in model control group (all P < 0.01). The Na(+) contents in hippocampus of Dip 25 mg/kg group and Dip 50 mg/kg group were 235 +/- 39 micro mol/g dry tissue and 223 +/- 36 micro mol/g dry tissue respectively, significantly lower than that in model control group (279 +/- 22 micro mol/g dry tissue, all P < 0.01). The K(+) content in hippocampus of Dip 25 mg/kg group and Dip 50 mg/kg group were 427 +/- 32 micro mol/g dry tissue and 434 +/- 29 micro mol/g dry tissue respectively, significantly higher than that in model control group (P < 0.05 and P < 0.01). The Na(+), K(+)-ATPase activity in the plasmalemma of brain cells in Dip 25 mg/kg group and Dip 50 mg/kg group was 649 +/- 45 and 1 198 +/- 218 micro mol pi/mg protein/min respectively, significantly higher than that in model control group (r = 0.9981, P < 0.01). The correlation between brain water content and Na(+), K(+)-ATPase activity was significant (r = -0.999 7, P < 0.01). CONCLUSION: Dip attenuates dose-dependently the increased H(2)O and Na(+) contents, prevents the decrease in potassium level, and accelerates the restoration of lowered Na(+), K(+)-ATPase activity resulted from cerebral ischemia, thus preventing ischemic brain edema.

Effects of dipfluzine on delayed afterdepolarizations and triggered activity induced by ouabain in guinea pig papillary muscles.

AIM: To investigate the effects of dipfluzine (Dip) on delayed afterdepolarizations (DADs) and triggered activity (TA) induced by ouabain and high Ca2+ in guinea pig papillary muscles. METHODS: Stable and reproducible DADs and TA in guinea pig papillary muscles were induced by ouabain (1 micromol/L) and high Ca2+ (5.4 mmol/L). DADs and TA were recorded using intracellular glass microelectrode technique. RESULTS: (1) DADs and TA were markedly inhibited by pretreatment with Dip (10, 30 micromol/L). The amplitude and duration of DADs were reduced by Dip (30 micromol/L) from 10.5 mV +/- 2.2 mV and 230 ms +/- 19 ms to 3.6 mV +/- 0.3 mV and 152 ms +/- 14 ms, respectively, and the induced time of DADs was prolonged from (21+/-5) to (66+/-11) min. TA was not observed. (2) Dip (10, 30 micromol/L) had significant therapeutic effects on DADs and TA. The amplitude and duration of DADs were reduced by Dip (30 micromol/L) from 10.4 mV +/- 1.2 mV and 218 ms +/- 22 ms to 3.3 mV +/- 0.6 mV and 159 ms+/-26 ms. The occurrence of TA was also abolished. CONCLUSION: Dip has inhibitory effects on DADs and TA induced by ouabain and high Ca2+ in guinea pig papillary muscles, which might be related to alleviation of intracellular calcium overload through inhibiting calcium channel and/or calcium release from sarcoplasmic reticulum. The effects of Dip on DADs and TA might produce anti-arrhythmic effects.

Effect of dipfluzine on L-type calcium current in guinea pig ventricular myocytes.

AIM: To study the effect of dipfluzine (Dip) on L-type calcium current in guinea pig ventricular myocytes. METHODS: Single myocytes were dissociated by enzymatic dissociation method. The current was recorded with the whole-cell configuration of the patch-clamp technique. RESULTS: Dip (0.3 - 30 micromol/L) reduced the voltage-dependently activated peak value of I(Ca-L) in a concentration-dependent manner. The characteristics of I-V relationship were not greatly altered by Dip, and the maximal activation voltage of I(Ca-L) in the presence of Dip was not different from that of control. Steady-state activation of I(Ca-L) was not affected markedly, and the half activation potential V(0.5)) and the slope factor (kappa) in the presence of Dip 3 micromol/L were not markedly different from those of the control. V(0.5) value was (-12.8 +/- 1.7) mV in the control and (-13.2 +/- 2.4) mV in the presence of Dip 3 micromol/L. The kappa value was (7.1 +/- 0.4) mV in the control and (7.5 +/- 0.5) mV in the presence of Dip 3 micromol/L (n = 7 cells from 3 hearts, P > 0.05). Dip 3 micromol/L markedly shifted the steady-state inactivation curve of I(Ca-L) to the left, and accelerated the voltage-dependent steady-state inactivation of calcium current. V(0.5) value was (-19.7 +/- 2.4) mV in the control and (-31 +/- 6) mV in the presence of Dip 3 micromol/L. The kappa value was (3.6 +/- 0.3) mV in the control and (1.8 +/- 0.2) mV in the presence of Dip 3 micromol/L (n = 4 cells from 2 hearts, P < 0.05). Dip 3 micromol/L markedly delayed half-recovery time of Ca2+ channel from inactivation from (40 +/- 11) to (288 +/- 63) ms (n = 4, P < 0.01). CONCLUSION: Dip mainly acts on the inactivated state of L-type calcium channel, accelerates the inactivation of calcium channel, and slows the recovery of calcium channel from inactivated state in guinea pig ventricular myocytes, through which the I(Ca-L) is inhibited.

Antagonistic effects of dipfluzine, flunarizine, and cinnarizine on 5-hydroxytryptamine-evoked contraction in pig basilar artery.

AIM: To investigate the effects of dipfluzine (Dip), a new derivative of cinnarizine (Cin), first developed by China, upon 5-hydroxytryptamine (5-HT)-induced contractions in cerebral arteries. METHODS: Compared Dip, flunarizine (Flu), and Cin antagonistic effects and actions on 2-component contractions evoked by 5-HT in isolated pig basilar artery. RESULTS: Dip showed a greater concentration-dependent antagonistic effect on 5-HT-evoked contraction than Cin and Flu in pig basilar artery rings. The order of potency (IC50) was Dip (4.0 mumol.L-1) > Flu (15.6 mumol.L-1) > Cin (25.2 mumol.L-1). All the Dip, Flu, and Cin inhibited 2-components of 5-HT-induced contraction. The antagonistic effects of Dip and Cin on the initial fast-phase contraction (FPC) were greater than that on the sustained tonic-phase contraction (STC), but Flu showed no difference between inhibiting effects on 2-component contractions. CONCLUSION: Dip was more potent than both of Flu and Cin on cerebrovascular dilation, associated mainly with the inhibition of intracellular calcium release.

Effects of dipfluzine on cortical somatosensory evoked potentials and amino acid contents in ischemic rat brain.

AIM: To evaluate the effects of dipfluzine ¿1-diphenyl-methyl-4-[3-(4-fluorobenzoyl)]-piperazine, Dip¿ on the intra- and extra-cellular contents of the amino acids in brain and the cortical somatosensory evoked potentials (SEP) in rats with cerebral ischemia. METHODS: Amino acids in micro-dialysates and brain tissue homogenates in female Wistar rats with bilateral carotid artery ligation (BCAL) were measured by HPLC and SEP was measured by the electrophysiological technique. RESULTS: Dip 50 mg.kg-1 i.p. prevented SEP from prolonging of the latency and overactivity of lowered amplitude, markedly lowered the elevation in extracellular level of glutamate (Glu), aspartate (Asp), and glycine (Gly) in intracerebral microdialysates, and alleviated the decrement of intracellular contents of Glu, Asp, Gly, taurine (Tau), and GABA in brain tissue. CONCLUSION: Dip reduced the disturbance of cortical function and the imbalance between excitatory and inhibitory amino acids in ischemic brain, therefore provided a further evidence for its protective effect on ischemic cerebral damage.

Effect of dipfluzine on platelet aggregation and thrombus formation.

Dipfluzine (Dip) is a novel diphenylpiperazine calcium channel blocker first synthesized in China. Effects of Dip on experimental thrombosis and platelet aggregation were studied in vitro and in vivo compared with cinnarizine (Cin). Dip 1 and 2 mg.kg-1 i.v. and incubated in 1-100 mumol.L-1 in vitro inhibited dose- or concentration-dependent rabbit platelet aggregation induced by ADP and by arachidonic acid (AA), respectively. Dip 2.5-10 mg.kg-1 i.v. and 50-100 mg.kg-1 ip inhibited the thrombosis in rats. Dip 10 mg.kg-1 i.v. and 200 mumol.L-1 depressed the in vitro thrombosis. These results suggest that attenuation of disturbed platelet-vessel wall reaction associated with platelet activation and vasoconstriction may be a main factor involved in the antithrombotic action of Dip, and that the effects of Dip were more potent than those of Cin.