Functional overlap of IP(3)- and cADP-ribose-sensitive calcium stores in guinea pig myenteric neurons.
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In myenteric neurons two different receptor subtypes govern the intracellular Ca(2+) stores: the inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R) and the ryanodine receptor (RyR). Their degree of functional overlap was determined by examining Ca(2+) release in these cells through both superfusion techniques and intracellular microinjection. Microinjection of IP(3) (50 microM) and cADP-ribose (cADPr, 50 microM), specific ligands for the IP(3)R and RyR, respectively, demonstrated mobilization of intracellular Ca(2+) stores. Perfusion with cinnarizine (50 microM) or dantrolene (10 microM), antagonists of the IP(3)R and RyR, respectively, eliminated the Ca(2+) response to microinjected IP(3) and cADPr. Superfusion of the neurons with 100 microM ATP, an IP(3)-mediated Ca(2+)-mobilizing agonist, caused intracellular Ca(2+) increments, which were antagonized by cinnarizine, and the RyR antagonists dantrolene, procaine (5 mM), and ryanodine (1 microM). Caffeine (10 mM) was applied repetitively in Ca(2+)-free conditions to deplete RyR-sensitive stores; subsequent perfusion with ATP demonstrated a Ca(2+) response. Conversely, caffeine caused a Ca(2+) response after repetitive ATP exposures. The internal Ca(2+) stores of myenteric neurons are governed by two receptor subtypes, IP(3)R and RyR, which share partial functional overlap. (+info)
Effect of dipfluzine on L-type calcium current in guinea pig ventricular myocytes.
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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. (+info)
Effects of dipfluzine on delayed afterdepolarizations and triggered activity induced by ouabain in guinea pig papillary muscles.
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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. (+info)
Parkinsonism and other movement disorders in outpatients in chronic use of cinnarizine and flunarizine.
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The purpose of this study is to determine the prevalence and the patterns of movement disorders (MD) in outpatients submitted to the chronic use of cinnarizine (cz) or flunarizine (fz), and to establish the main risk factors for MD development. Over a period of 3 months, data were collected from outpatients who were chronic users of cz or fz in a municipal health institute. A total of 26 outpatients were included and all of them were submitted to a protocol that included DSM-4 diagnosis criteria for drug-induced movement disorders, parkinsonism (PK) and depression. Parkinsonism was diagnosed in 34% of the patients, PK plus akathisia, PK plus akathisia and bucco-linguo-masticatory syndrome (BLMS), isolated BLMS and dystonia were found in 4% patients each. Patients with BLMS had the highest median age and the longest average period in which they used the drugs. The affected group, when compared to the non-affected one, presented with higher rates of depression. This study demonstrates the existence of a direct relationship between the time of use of cz and fz, the age and the prevalence of PK and other MD. It also suggests that these drugs increase the incidence of depression. (+info)
Pediatric cinnarizine overdose and toxicokinetics.
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Cinnarizine, a piperazine derivative, is a widely prescribed medication for the treatment of vestibular disorders and motion sickness. Cinnarizine has antihistaminic, antiserotoninergic, antidopaminergic, and calcium channel-blocking properties. We present the first report in the English literature of cinnarizine poisoning and toxicokinetics. A 30-month-old toddler ingested 225 mg of cinnarizine, 18 times the recommended dose for older children. Four hours later, she became jittery with a wide-based gait and vomited 3 times. She was examined by her family physician, who reported stupor and twitching in both hands. On admission to the hospital, 6 hours after the ingestion, she was stuporous and had 3 short, generalized tonic-clonic convulsions that were controlled with a single dose of midazolam. Full clinical recovery was seen 10 hours after ingestion. Serum cinnarizine levels were 7407, 2629, and 711 ng/mL on admission and at 4 and 12 hours thereafter, respectively, 26.9 times higher than the therapeutic levels in adults. Elimination rate constant, calculated by linear regression of the ln concentrations of the 3 data points, was 0.19. Half-life, calculated from the equation t(1/2) = 0.693/kel, where kel is the elimination rate constant, was 3.65 hours. The manufacturing company revealed that their database contains 23 reports of cinnarizine overdose (adult and children), received between 1972 and 2004. Clinically, these cases reflect mainly symptoms of alterations in consciousness ranging from somnolence to stupor and coma, vomiting, extrapyramidal symptoms, and hypotonia. In a small number of young children, convulsions developed; recovery was uneventful in 4 cases and not reported in 1. The neurologic complication may be explained by the antihistaminic effect of cinnarizine because central nervous system depression and convulsions are known complications of antihistaminic overdose. It is hypothesized that cinnarizine-induced convulsions also are related to the antidopaminergic effect of the drug. Apart from the convulsions, no other adverse effects related to calcium channel-blocking properties, such as bradycardia or hemodynamic instability, were observed. Pediatric patients with cinnarizine overdose need to be observed in a health care facility for potential neurologic complications and be treated symptomatically. The delay to onset of clinical effect should be considered in the observation period. (+info)
Optimizing the pharmacological component of integrated balance therapy.
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Drug treatment is an important option for the treatment of peripheral vestibular diseases. AIM: To identify the drug component associated with optimal integrated balance therapy (IBT) for Menieres disease or other peripheral vestibular disorders. MATERIALS AND METHODS: Analysis of a series of patients with Menieres disease patients or patients with other peripheral vestibular disorders that received IBT involving either no medication or betahistine, cinnarizine, clonazepam, flunarizine or Ginkgo biloba during 120 days. RESULTS: In Menieres disease, significant differences were observed for all drug therapies (60 days) versus no medication; betahistine was significantly more effective than all other drugs at 60 and 120 days. For non-Menieres disorders, significant differences were observed among betahistine, cinnarizine, clonazepam and flunarizine and no medication after 60 days; all drug therapies were significantly more effective than no medication after 120 days; betahistine, cinnarizine or clonazepam were equally effective and betahistine was more effective than flunarizine and EGb 761. All treatment options were well tolerated. CONCLUSIONS: Drug therapies were more effective than no medication in the IBT for patients with Menieres disease or other peripheral vestibular disorders. Betahistine was the most effective medication for patients with Menieres disease and was as effective as cinnarizine and clonazepam for other peripheral vestibular disorders. (+info)
Cinnarizine in refractory migraine prophylaxis: efficacy and tolerability. A comparison with sodium valproate.
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High-performance liquid chromatographic assay for cinnarizine in human plasma.
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The high performance liquid chromatography for the determination of cinnarizine in human plasma is described. The procedure involves liquid-liquid extraction followed by reversed phase high-performance chromatographic analysis with fluorometric detection. The method was validated for accuracy, precision, specificity, linearity, sensitivity, recovery, and stability. No endogenous compounds were found to interfere. The absolute extraction recovery of cinnarizine and clocinizine (internal standard) from plasma samples were 97% and 89%, respectively. The linearity was assessed in the range 1-100 ng/mL. The intra-day and inter-day relative standard deviations were less than 10%, and the accuracy of the assay expressed by bias was in the range 0.14-2.37%. The method was proved to be suitable for human pharmacokinetic studies following single oral dose. (+info)