Drp-1, a potential therapeutic target for brain ischaemic stroke

BACKGROUND AND PURPOSE

The resistance of CA3 neurons to ischaemia and the ischaemic tolerance conferred by ischaemic preconditioning (IPC) are two well-established endogenous neuroprotective mechanisms. Elucidating the molecules involved may help us find new therapeutic targets. Thus, we determined whether dynamin-related protein 1 (Drp-1) is involved in these processes.

EXPERIMENTAL APPROACH

In vivo, we subjected rats to either 10 min severe global ischaemia using a four-vessel occlusion (4-VO) model or 2 min IPC before the onset of 4-VO. In vitro, we performed oxygen glucose deprivation (OGD) studies in rat hippocampal neurons. Drp-1 was silenced or inhibited by siRNA or pharmacological inhibitor Mdivi1. To assess whether mitochondrial Drp-1 alters neuronal vulnerability to ischaemic injury, various approaches were used including western blot, immunohistochemistry, immunofluorescence staining and electron microscopy. Hippocampal function was assessed using an open-field test.

KEY RESULTS

Mitochondrial dynamin-related protein 1 (mtDrp-1) was selectively induced by ischaemia in hippocampal CA3 neurons. In hippocampal CA1 neurons, mtDrp-1 was not affected by ischaemia but significantly up-regulated by IPC. Suppression of Drp-1 increased the vulnerability of cells to OGD and global ischaemia. Inhibition of Drp-1 in vivo resulted in loss of acquisition and encoding of spatial information, and also prevented ischaemia-induced mitophagy in CA3. Thus mitochondrial-mediated injury was amplified and resistance to ischaemic injury lost.

CONCLUSIONS AND IMPLICATIONS

Our findings that Drp-1 increases the resistance of neurons of hippocampal CA3 affected by global ischaemia and contributes to the tolerance conferred by IPC highlight Drp-1 as a potential therapeutic target for brain ischaemic stroke.

Changes of snoring sound after relocation pharyngoplasty for obstructive sleep apnoea: the surgery reduces mean intensity in snoring which correlates well with apnoea-hypopnoea index

OBJECTIVE

To investigate objective changes of snoring after surgery in patients with obstructive sleep apnoea (OSA) and correlate these with changes in the apnoea-hypopnoea index (AHI).

DESIGN

Prospective case series.

SETTING

A novel measurement, Snore Map, was used to analyse full-night snore sounds in terms of the maximal/mean intensity, peak/mean frequency, snoring index and energy type (Snore Map type, 0-4). Snore sound was classified into three bands according to frequency energy spectrum: B1 (40-300 Hz), B2 (301-850 Hz) and B3 (851-2000 Hz).

PARTICIPANTS

Thirty-four male and two female OSA patients (mean age, 39 years; mean AHI, 53.1/h; mean body mass index, 26.8 kg/m(2) ) with favourable anatomic structure were consecutively enrolled.

MAIN OUTCOME MEASURES

Parameters of polysomnographies and Snore Maps at baseline and six months after operation were compared. Statistical significance was set at P < 0.05.

RESULTS

Thirty-two patients completed this study. The mean reduction in the total-snoring index was insignificant but there were significant decreases in total mean intensity, total peak frequency, total mean frequency and Snore Map type after surgery. There were also significant decreases in the mean intensity in all three bands, the snoring index in B2/B3 and the mean frequency in B1 postoperatively. Changes in the total mean intensity, total mean frequency, B2 mean intensity and B3 snoring index positively correlated with change in the AHI.

CONCLUSIONS

Relocation pharyngoplasty significantly decreases both the snoring sound intensity and snoring frequency. These reductions are directly proportional to the improvement of OSA.

Claulansine F suppresses apoptosis induced by sodium nitroprusside in PC12 cells

Reactive oxygen species (ROS) are known to be involved in many neurodegenerative diseases. This study assessed the effect of Claulansine F, a new carbazole isolated from Clausena lansium, on sodium nitroprusside (SNP)-treated rat pheochromocytoma PC12 cells. First, it was found that Claulansine F showed more potential on inhibiting the programmed death of PC12 cells than edaravone by cell viability, morphologic observation, and flow cytometric analysis. Further results also showed that Claulansine F attenuated the production of total intracellular ROS formation and lipid peroxidation in PC12 cells, inhibited the mitochondrial membrane potential (MMP) loss, and prevented the programmed cell death event via the P53/Bcl-2 family pathway. Its protective effect was likely medicated by the hydroxyl radical (·OH) scavenging ability, as it appeared to be not involved in the natural antioxidant system. These results suggested a promising potential for Claulansine F as a ROS scavenger in pathologies, where an oxidative stress is involved.

IMM-H004, a novel coumarin derivative compound, protects against amyloid beta-induced neurotoxicity through a mitochondrial-dependent pathway

We have investigated the effect of IMM-H004 (7-hydroxy-5-methoxy-4-methyl-3-(4-methylpiperazin-1-yl)-2H-chromen-2-one), a coumarin derivative, on the amyloid beta (Aβ)-induced neurotoxicity in primary culture cortical neurons and pheochromocytoma (PC12) cells. Our results showed that treatment with IMM-H004 markedly reduced the number of apoptotic cells after exposure to Aβ25-35 or Aβ1-42, determined by MTT, TUNEL staining and Flow cytometry. Further study indicated that IMM-H004 significantly inhibited Aβ-induced cytotoxicity and apoptosis by reversing Aβ-induced mitochondrial dysfunction, including MMP (mitochondrial membrane potential) decrease, reactive oxygen species production, and mitochondrial release of cytochrome c. IMM-H004 can regulate the interaction between Bax and Bcl-2, decreased levels of p53 and active caspase-3 protein induced by Aβ25-35. Furthermore, IMM-H004 also reduced translocation of AIF (apoptosis-inducing factor) induced by Aβ25-35. These results demonstrated that IMM-H004 was capable of protecting neuronal cells from Aβ-induced degeneration through a mitochondrial-dependent apoptotic pathway. The results of this study lend further credence to the notion that IMM-H004 is a 'multipotent therapeutic agrent' that reduces toxic levels of brain Aβ, and holds the potential to protect neuronal mitochondrial function in Alzheimer's disease.

Effects of Anti-Bursin Monoclonal Antibody on Immunosuppression in the Duck (Cherry Valley Duck)

To study the immunologic function of bursin, we analyzed the effects of anti-bursin monoclonal antibody (mAb) on the immunosuppression in ducks (Cherry Valley duck) by injecting various doses of the anti-bursin mAb into 13-d duck embryos. After hatch, cell-mediated immune activity and humoral responses were studied using lymphocyte proliferation test, tube agglutination test, and indirect enzyme-linked immunosorbent assay to detect anti-Escherichia coli antibodies and antibodies to Riemerella anatipestifer, respectively. Simultaneously, relative weights (BW-adjusted) of bursa of Fabricius (BF), spleen, and thymus were determined. Additionally, the morphology of BF, spleen, and thymus was examined at various ages using conventional histology. Follicle morphology of BF was analyzed by image analysis. The results indicated that anti-bursin mAb markedly decreased duck lymphocyte proliferation, the antibody-producing ability to bacteria, as well as the relative BF weight. Moreover, the anti-bursin mAb hindered the development of BF follicles.

Combined bronchoalveolar lavage and polymerase chain reaction in the diagnosis of pulmonary tuberculosis in smear-negative patients

SETTING

The polymerase chain reaction (PCR) may be sensitive and specific for the diagnosis of tuberculosis, but most reports are of studies conducted in well-controlled laboratories. A study to evaluate the clinical value of bronchoalveolar lavage (BAL) combined with PCR was necessary.

OBJECTIVE

One hundred and thirty one patients were recruited into the study from March 1994 to February 1997.

DESIGN

Patients with a positive acid-fast stain on sputum smear were recruited into group A as positive controls, patients with lung cancer and a negative acid-fast stain on sputum smear were put into group B as negative controls, and patients who had clinical symptoms of pulmonary TB without sputum or with negative smear results were the investigating group. PCR was performed on the sputum samples from group A and B patients and on the BAL fluid from those in group C.

RESULTS

The sensitivity of PCR was 96% in group A, and the specificity was 100% in group B. The sensitivity of PCR in the BAL fluid from the group C patients was 36% and the specificity was 96%; the positive predictive value was 94% and the negative predictive value was 45%.

CONCLUSION

BAL plus PCR is useful in the rapid diagnosis of pulmonary TB in non-productive or smear-negative patients.

Neuronal activity in dorsomedial frontal cortex and prefrontal cortex reflecting irrelevant stimulus dimensions

Previous studies of the dorsomedial frontal cortex (DMF) and the prefrontal cortex (PF) have shown that, when monkeys respond to nonspatial features of a discriminative stimulus (e.g., color) and the stimulus appears at a place unrelated to the movement target, neurons nevertheless encode stimulus location. This observation could support the idea that these neurons always encode stimulus location, regardless of its relevance to an instrumentally conditioned behavior. Past studies, however, leave open the possibility that activity observed during one operant task might reflect the contingencies of a different task, performed at different times. To test these alternatives, we examined the activity of DMF and PF neurons in two rhesus monkeys conditioned to perform an operant eye-movement task in which only the color and shape of visual stimuli served as salient discriminative features. Each of eight stimuli was associated with a response to a different eye-movement target. The location of these stimuli varied from trial to trial but was of no behavioral relevance, and the monkeys did not perform any operant task in which stimulus location controlled behavior. A substantial minority of neurons in both DMF and PF nevertheless encoded stimulus location, which indicates that this property does not depend on its relevance in an instrumentally conditioned behavior.

Spontaneous variability of cardiac output in ventilated critically ill patients

OBJECTIVE

To define the magnitude of spontaneous cardiac output variability over time in sedated medical intensive care unit patients attached to a continuous cardiac output monitor, and to determine whether high level positive end-expiratory pressure or inverse inspiratory-to-expiratory (I:E) ratio ventilation resulted in greater variability over time than low positive end-expiratory pressure with conventional I:E ratio ventilation.

DESIGN

Prospective study.

SETTING

Medical intensive care unit in a tertiary medical center.

PATIENTS

A total of 22 hemodynamically stable acute respiratory failure patients with a pulmonary artery catheter inserted for hemodynamic monitoring

INTERVENTIONS

After being sedated, patients were randomized ultimately to receive pressure control ventilation first at setting A (high positive end-expiratory pressure [15 cm H2O] with conventional I:E ratio [1:2]) and then at setting B (low positive end-expiratory pressure [5 cm H2O] with inverse I:E ratio [2:1]), or vice versa, and then at setting C (low positive end-expiratory pressure [5 cm H2O] with conventional I:E ratio [1:2]). Each ventilation setting period lasted 1 hr.

MEASUREMENTS AND MAIN RESULTS

Cardiac output (CO) was measured continuously. The continuous CO value displayed was updated every 30-60 secs. The updated value reflected an average of the previous 3-6 mins. The coefficient of variation (CV) of CO for each setting in each patient was calculated to represent the spontaneous variability. The mean CO+/-SD and CV of each setting was 5.7+/-1.8 L/min and 4.4% for setting A, 5.6+/-1.5 L/min and 4.6% for setting B, and 5.9+/-1.7 L/min and 4.8% for setting C. Analysis of variance revealed no significant differences between the CVs of the three settings. The 95% confidence interval for the COs for each setting was approximately the mean CO+/-0.1 x mean CO measured.

CONCLUSIONS

In critically ill sedated medical intensive care unit patients with stable hemodynamics, the spontaneous variability of cardiac output over time was not significant. High positive end-expiratory pressure (15 cm H2O) and inverse ratio ventilation (2:1) did not contribute to increased spontaneous variability of cardiac output.

Tuberculin purified protein derivative up-regulates the telomerase activity of peripheral blood mononuclear cells from patients with pulmonary tuberculosis

Telomerase activity was detectable in cells of tuberculous pleural effusions at high percentage. To investigate the possible role of telomerase in the immune function, we examined the proliferating state and the expression of telomerase activity in peripheral blood mononuclear cells (PBMC) from 13 patients with pulmonary tuberculosis (TB) and 13 healthy volunteers in response to tuberculin purified protein derivative (PPD) challenge. Exposure of cells to phytohemagglutinin (PHA) significantly promoted PBMC proliferation during a 6 day-period in both TB patient and healthy volunteer groups. PPD treatment also significantly promoted PBMC proliferation during a 6 day-period in TB patient group, but had no significant effect in healthy volunteer group. During the same period, telomerase activity was detected in every PHA- and PPD-treated samples of the TB patient group. However, the telomerase activity was not detected in PPD-treated samples from healthy donors and all the untreated samples. Our results indicate that the telomerase activity in PBMC could be induced by PPD stimulation in TB patients. Telomerase activity may thus play a permissive role in cell division and clonal expansion of the immune cells in response to TB.

Spontaneous variability of arterial oxygenation in critically ill mechanically ventilated patients

OBJECTIVE

To assess the magnitude of spontaneous variability of arterial oxygenation and oxygen tension-based indices over time in medical intensive care unit (ICU) patients and to study whether high positive end-expiratory pressure (PEEP) or inverse inspiratory-to-expiratory (I:E) ratio ventilation (IRV) results in a greater variability than low PEEP with conventional I:E ratio ventilation.

DESIGN

Prospective study.

SETTING

Medical ICU in a tertiary medical center.

PARTICIPANTS

23 patients requiring a pulmonary artery floating catheter for hemodynamic monitoring.

INTERVENTION

After being completely sedated, patients were randomized to receive pressure-control ventilation at setting A: high PEEP (15 cm H2O) with conventional I:E ratio (1:2) and setting B: inverse I:E ratio (2:1) with low PEEP (5 cm H2O) alternately, and then at setting C: low PEEP (5 cm H2O) with conventional I:E ratio (1:2). Each ventilation setting lasted 1 h.

MEASUREMENTS AND RESULTS

The arterial and mixed venous blood samples were measured simultaneously at baseline (time 0), and at 15, 30, 45, and 60 min thereafter. The coefficient of variation (CV) of arterial oxygen tension (PaO2) over time was 5.9 % for setting A, 7.2 % for setting B, and 6.9 % for setting C. ANOVA showed no significant differences in CVs of PaO2 between the three settings. Oxygen tension-based indices, alveolar-arterial oxygen difference (A-aDO2) and PaO2/ PAO2 (alveolar oxygen tension), displayed CVs equal to that of PaO2; the CV of A-aDO2/PaO2 was significantly greater than that of PaO2.

CONCLUSIONS

In critically ill medical ICU patients, despite sedation, the spontaneous variability in PaO2 over time is substantial. A high PEEP or IRV does not contribute to the increased variation in PaO2.

Serodiagnosis of tuberculosis by enzyme-linked immunosorbent assay for anti-A60 and anti-A38

BACKGROUND

For early diagnosis of tuberculosis (TB), especially in the patients without adequate sputum specimens for examination, we found a simple, rapid and inexpensive method among many current available diagnostic tools, the enzyme-linked immunosorbent assay (ELISA). To investigate the diagnostic effectiveness of this method, we applied ELISA for detection of antigen 60 IgG and IgM as well as antigen 38 IgG antibodies at Chang Gung Memorial Hospital from April 1995 through June 1996.

MATERIALS AND METHODS

Sixty-seven patients were enrolled and divided into 3 groups, Group A (n = 24), patients with positive sputum acid-fast stain; Group B (n = 18), patients with lung cancer and negative sputum acid-fast stain; and Group C (n = 25), patients with chest roentgenogram (CXR) which were suggestive of TB but with negative acid-fast stain results or no sputum for examination.

RESULTS

For the A60 IgG antibody, we found a sensitivity rate of 91.7% for Group A and Group B, and 85.7% for Group C as well as an overall sensitivity of 89.5% but with lower specificity. For the A60 IgM antibody, a lower sensitivity (37.5%, 14.3%, 28.9%, respectively) was found but with higher specificity. For the A38 IgG antibody, we found a lower sensitivity (40%, 11.1%, 31%, respectively) but with higher specificity (100%, 71.4%, 90%, respectively).

CONCLUSION

With a high sensitivity but low specificity for diagnosis of TB, A60 IgG ELISA could be used as a rapid, simple screening test for patients with results suggestive of TB, especially in those who had no sputum or had negative sputum acid-fast stain results. Otherwise, A60 IgM or A38 IgG ELISA, with a high specificity, could be used as a reliable test in the diagnosis of pulmonary TB when the result is positive. In summary, although ELISA is a simple, rapid, inexpensive method, it is helpful but limited in the diagnosis of pulmonary TB.

[Neuronal activity of monkey dorso-lateral premotor cortex during tasks of figure recognition guided motor sequence vs memorized spatial motor sequence]

In the last 2-3 decades the role of the premotor cortex (PM) of monkey in memorized spatial sequential (MSS) movements has been amply investigated. However, it is as yet not known whether PM participates in the movement sequence behaviour guided by recognition of visual figures (i.e. the figure-recognition sequence, FRS). In the present work three monkeys were trained to perform both FRS and MSS tasks. Postmortem examination showed that 202 cells were in the dorso-lateral premotor cortex. Among 111 cells recorded during the two tasks, more than 50% changed their activity during the cue periods in either task. During the response period, the ratios of cells with changes of firing rate in both FRS and MSS were high and roughly equal to each other, while during the image period, the proportion in the FRS (83.7%) was significantly higher than that in the MSS (66.7%). Comparison of neuronal activities during same motor sequence of two different tasks showed that during the image periods PM neuronal activities were more closely related to the FRS task, while during the cue periods no difference could be found. Analysis of cell responses showed that the neurons with longer latency were much more in MSS than in FRS in either cue or image period. The present results indicate that the premotor cortex participates in FRS motor sequence as well as in MSS and suggest that the dorso-lateral PM represents another subarea in function shared by both FRS and MSS tasks. However, in view of the differences of PM neuronal responses in cue or image periods of FRS and MSS tasks, it seems likely that neural networks involved in FRS and MSS tasks are different.

Arterial oxygenation is unchanged during hemodialysis in patients mechanically ventilated in assist-control mode

Dialysis-induced hypoxemia can occur in spontaneously breathing renal failure patients but whether it occurs during bicarbonate hemodialysis in critically ill patients receiving mechanical ventilation in assist-control mode is not clear. Twenty-one patients admitted to the medical intensive care unit who required mechanical ventilation and hemodialysis with the use of a cuprammonium dialyzer were enrolled and 25 sessions of hemodialysis were performed. Arterial blood gas, white blood cell count, minute ventilation, respiratory rate, and blood pressure were measured before dialysis (time 0) and at 15, 30, 60, 120, 180, and 240 minutes thereafter. The white blood cell count dropped immediately and reached the nadir 15 minutes after hemodialysis began. Thereafter, it recovered and overshot the predialysis value at the end of dialysis. The serum HCO3- concentration increased progressively after dialysis began and resulted in significant metabolic alkalosis. The P (A-a)O2 was not aggravated and minute ventilation was not depressed by rapid metabolic alkalosis under mechanical ventilatory support. The PaO2 remained stable throughout hemodialysis. No significant hypoxemia occurred in groups of varying predialysis cardiopulmonary dysfunction. These findings suggest that in renal failure patients ventilated in assist-control mode, l) hypoventilation and accompanying hypoxemia did not occur during bicarbonate (35 mEq/L) dialysis, despite significant metabolic alkalosis; and 2) patients with higher Acute Physiologic and Chronic Health Evaluation (APACHE) III scores and P(A-a)O2 levels were not more prone to dialysis-induced hypoxemia.

Potential misconceptions in dopamine transporter assays arising from the binding of [125I]RTI-121 to filters: effect of ions and cocaine

Binding of the cocaine analog 3 beta-(4-[125I]iodophenyl)tropane-2 beta-carboxylic acid isopropyl ester ([125I]RTI-121) to filters was studied in order to assess its contribution to labeling dopamine transporters on rat striatal synaptosomal membranes in filtration assays. Filter binding (FB) decreased with increasing Na+. Cocaine (30 and 100 microM) substantially reduced the FB at low Na+ with much less of an effect at higher Na+. Similar results were observed with K+. At 10 mM Na+, RTI-121 (1 microM) displaced the FB to the same degree as cocaine (100 microM); mazindol (10 microM), BTCP (1 microM), and dopamine (1 mM) did so to a lesser degree; and GBR12935 (1 microM) did not. If the specific binding was calculated without deducting the FB displaced with cocaine (DFB), the DFB accounted for 15-19% of the 'specific binding' at 10 mM Na+ in the assay. This additional binding population resulted in an upward curvilinear Scatchard plot and incorrect estimation of equilibrium binding parameters and ion potencies. At 10 mM Na+, without deduction of DFB, the high-affinity component had a Kd of 3.4 nM and Bmax of 2.4 pmol/mg protein, and the respective values for the low-affinity component were 84 nM and 16 pmol/mg protein; when DFB was deducted, one component was observed with a Kd of 4.4 nM and Bmax of 3.3 pmol/mg protein. The presence of higher Na+ in the assay diminished these artifacts. Thus, at 150 mM Na+, without deduction of DFB, there was one binding component with a Kd of 3.9 nM and Bmax of 4.6 pmol/mg protein; these values became 3.3 nM and 3.8 pmol/mg protein when DFB was deducted.

Modeling of the interaction of Na+ and K+ with the binding of the cocaine analogue 3beta-(4-[125I]iodophenyl)tropane-2beta-carboxylic acid isopropyl ester to the dopamine transporter

The present study examines the interaction of Na+ and K+ with the binding of the cocaine analogue 3beta-(4-[125I]iodophenyl)tropane-2beta-carboxylic acid isopropyl ester to dopamine transporters (DATs) in rat striatal synaptosomal membranes at 37 degrees C. The binding increases with [Na+] from 10 to 100 mM and decreases with higher [Na+]. The presence of K+ reduces the maximal stimulatory effect of Na+ and causes a nonlinear EC50 shift for Na+. K+ strongly inhibits the binding at low [Na+]. Increasing [Na+] produces a linear IC50 shift for K+. Saturation analysis indicates a single binding site changing its affinity for the radioligand depending on [K+]/[Na+] ratio in the assay buffer. A reduced Bmax was observed in the presence of 10 mM Na+ and 30 mM K+. Both high [Na+] and high [K+] accelerate the dissociation of the binding, and K+-induced acceleration was abolished by increasing [Na+]. Least squares model fitting of equilibrium data and kinetic analysis of dissociation rates reveal competitive interactions between Na+ and K+ at two sites allosterically linked on the DAT: One site mediates the stimulatory effect of Na+, and the other site involves the radioligand binding and the inhibitory effect of cations on the binding. Various uptake blockers and substrates, dopamine in particular, display reduced potency in inhibiting the binding at a higher [K+]/[Na+] ratio.

Pharmacology and regulation of the neuronal dopamine transporter

The dopamine transporter, a member of the family of Na+,Cl(-)-dependent transporters, mediates uptake of dopamine into dopaminergic neurons by an electrogenic, Na(+)- and Cl(-)-transport-coupled mechanism. Dopamine and blockers of uptake such as cocaine probably bind to both shared and separate domains on the transporter, which can be influenced dramatically by the presence of cations. Regulation of the dopamine transporter occurs both by chronic occupancy with blocker and by acute effects of D2 dopamine receptors or second messengers such as diacylglycerol (protein kinase C) and arachidonic acid. The dopamine transporter is involved in the uptake of toxins generating Parkinson's disease; it is also an important target for psychostimulant drugs, ligands for in vivo imaging and medications used for neurologic diseases involving changes in the dopamine system.

Effects of different perfusion medium on the extracellular basal concentration of dopamine in striatum and medial prefrontal cortex: a zero-net flux microdialysis study

The zero-net flux microdialysis method was used to determine (1) the basal concentration of dopamine (DA) in the extracellular space, and (2) the in vivo recovery of Da in the striatum and the medial prefrontal cortex by using three different kinds of perfusion medium. They were, (a) commercial Ringer's solution, (b) low Ca2+ Ringer's solution, and (c) artificial cerebrospinal fluid (aCSF). Our results not only support previous findings that the high Ca2+ concentration in the perfusion medium could increase the baseline concentration of DA in the dialysate, which was collected from extracellular space through dialysis probe; but also provides evidence that this baseline increase was primarily due to an increase of basal DA concentration, and not from the increase of the in vivo recovery. Additionally, there was no significant difference in the basal DA concentration by using either commercial Ringer's solution or aCSF. This indicates that both commercial Ringer's solution and aCSF are suitable as good perfusion medium to determine the basal DA in the rat's brain.

Characterization of [125I]RTI-121 binding to dopamine transporter in vitro

AIM

To characterize the binding of [125I]3 beta-(4-iodophenyl) tropane-2 beta-carboxylic acid isopropyl ester (RTI-121) to the dopamine transporter (DAT) under physiologically relevant conditions.

METHODS

[125I]RTI-121 was used to label the DAT on fresh rat striatum synaptosomal membranes in artificial cerebrospinal fluid (ACSF) at 37 degrees C.

RESULTS

[125I]RTI-121 binding reached equilibrium within 3 min and remained at its plateau value for at least 9 min. The data from kinetic, saturation, and competition studies supported a one-site model for the binding of [125I]RTI-121 to the DAT. Various DAT blockers (oocaine, GBR12935, and BTCP) and substrates (dopamine and d-amphetamine) competitively inhibited the binding of [125I]RTI-121. Compared with NaPhos-KCl-NaCl assay buffer, ACSF containing Ca2+ and Mg2+ markedly increased the IC50 of DAT blockers for inhibiting [125I]RTI-121 binding with less effect on that of substrates. Various D2 receptor ligands (pergolide, quinirole, sulpiride, and l-stepholidine) had no direct effect on the binding of [125I]RTI-121.

CONCLUSION

[125I]RTI-121 binding under physiologically relevant conditions fulfills the basic criteria for DAT binding assay.

Comparison of the clinical diagnostic value between pleural needle biopsy and analysis of pleural effusion

BACKGROUND

Many diseases are manifested by pleural effusion. Chest echo-guided thoracentesis and pleural biopsy are the two major procedures in diagnosing pleural effusion, but the validity is still under debate. To compare the diagnostic value of echo-guided pleural biopsy with pleural effusion analysis, we designed this retrospective study.

METHODS

We reviewed 176 patients who underwent both procedures at Chang Gung Memorial Hospital from 1989 to 1990.

RESULTS

Sixty-six patients (38%) were diagnosed with malignant pleural effusion which was proven by needle biopsy (55%) or effusion cytologic analysis (64%). Combining both methods increased the diagnostic rate to 88%. Among the 76 patients who were diagnosed with tuberculous pleural effusion, only 18% were proven by pleural biopsy and 20% by pleural effusion culture. The other cases were confirmed by sputum exam (34%) or successful therapeutic trial (41%). The remaining 19 patients (11%) were diagnosed as undeterminate etiology.

CONCLUSION

Combined pleural biopsy with cytologic analysis of the pleural effusion was more beneficial than any single method in identifying malignant pleural effusions, and repeated pleural biopsy increased the positive rate from 49% to 55% in our study.

Binding of the [125I]3 beta-(iodophenyl)tropan-2 beta-carboxylic acid isopropyl ester to the dopamine transporter at a physiologically relevant temperature: mutually exclusive binding and different ionic requirements for various uptake blockers and substrates

The present study describes the binding of cocaine analog [125I]3 beta-(iodophenyl)tropan-2 beta-carboxylic acid isopropyl ester ([125I]RTI-121), a highly selective ligand for the dopamine transporter (DAT), to rat striatal synaptosomal membranes at 37 degrees C. Saturation analysis of [125I]RTI-121 binding revealed a single binding site with similar affinity for RTI-121 at both 50 and 134 mM NaCl. However, the density of binding sites was reduced at 134 mM NaCl. Various uptake blockers and substrates of the DAT monophasically inhibited the specific binding of [125I]RTI-121. Increasing the NaCl concentration from 50 mM to 134 mM enhanced the affinity of the substrate dopamine and amphetamine for the DAT, without affecting that of the uptake blockers. At 134 mM NaCl, the copresence of GBR12935, BTCP, cocaine, amphetamine, or dopamine decreased the affinity of RTI-121 to the extent predicted by a model in which the binding of all compounds is mutually exclusive. This, along with a different NaCl sensitivity for blockers and substrates, suggests that the two categories of compounds recognize nonidentical but overlapping binding domains on the DAT. In contrast, the mutually exclusive binding with similar NaCl sensitivity for RTI-121 and the other uptake blockers tested here suggests the involvement of common binding domains in the recognition of these blockers.

Intrategmental infusion of cocaine decreases dopamine release and enhances norepinephrine release in the medial prefrontal cortex

We evaluated the effects of local cocaine infusion into the A10 (ventral tegmental area), the cell body of the mesocorticolimbic dopaminergic pathway, on the extracellular concentrations of dopamine and norepinephrine in the medial prefrontal cortex, one of its terminal fields. A 1-ml Hamilton syringe was used to infuse a cocaine solution, either 20 or 200 microM, into the ventral tegmental area of anesthetized rats for 120 min through a microdialysis probe. The pure artificial cerebrospinal fluid (0 microM cocaine) infusion served as a control and a lidocaine (100 microM) infusion was administered to prevent the local anesthetic effect of cocaine. After intrategmental cocaine infusion (either 20 or 200 microM), extracellular dopamine and norepinephrine in the ventral tegmental area both increased significantly to a steady state level (208 +/- 42 and 148 +/- 23% for low dose and 220 +/- 24 and 150 +/- 15% for high dose). Simultaneously, the 200-microM cocaine infusion caused a significant decrease in extracellular dopamine (77 +/- 5%) but an increase in norepinephrine (140 +/- 6%) in the medial prefrontal cortex. The local anesthetic, lidocaine, produced no effects on the dopamine or norepinephrine output (neither in the ventral tegmental area nor in the medial prefrontal cortex). This study not only supports recent findings of an increase in extracellular dopamine and norepinephrine in the ventral tegmental area on intrategmental cocaine infusion, but also demonstrates that cocaine infused locally in the ventral tegmental area can decrease dopamine and increase norepinephrine at a remote terminal area (medial prefrontal cortex). Finally, the introduction rate of cocaine into the ventral tegmental area by retrograde microdialysis was found to be 0.83 ng/min for the low dose and 8.14 ng/min for the high dose.

[3H]WIN 35,428 [2 beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane] binding to rat brain membranes. Comparing dopamine cell body areas with nerve terminal regions

Potential differences between somatodendritic acid and axonal dopamine transporters were examined by comparing the binding constants of [3H]WIN 35, 428 [2 beta-carbomethoxy- 3 beta-(4-fluorophenyl)tropane] binding to membranes prepared from the rat ventral mesencephalon, containing A9 and A10 dopamine cell bodies, and from the nucleus accumbens. Saturation analysis of [3H]WIN 35,428 binding, in the presence of compounds to occlude norepinephrine and serotonin transporters, was performed by both the "unlabeled" method (varying unlabeled ligand) and "labeled" method (varying radioligand). The density of binding was substantially lower in the ventral mesencephalon than in the nucleus accumbens, but the binding affinity was only slightly different. Likewise, the differences between the two regions in the inhibitory potency of cocaine and GBR 12909 [1-(2-di(4-fluorophenyl)-methoxy-ethyl)4-(3-phenylpropyl)piperazine] were not substantial. The results suggest that somatodendritic and axonal dopamine transporters in the ventral mesencephalon and nucleus accumbens are not very different as far as their binding domains for uptake blockers such as cocaine and GBR 12909 are concerned.

Amygdala kindling of forebrain seizures and the occurrence of brainstem seizures in genetically epilepsy-prone rats

Forebrain seizures were kindled in rats by daily electrical stimulation of the amygdala. Genetically epilepsy-prone rats scoring 9 (GEPR-9s) on the seizure severity scale during audiogenic seizure (AGS) screening ("brainstem seizure-experienced") required fewer stimulations to achieve fully kindled seizures (forelimb clonus with rearing and falling) than control rats. AGS-naive GEPR-9s required an intermediate number of stimulations, indicating a role for both genetic predisposition and previous acoustically evoked brainstem seizure experience. Other forebrain kindling indices such as afterdischarge threshold/duration and seizure latency/duration also involved genetic as well as phenotypic (previous seizure experience) factors. In most GEPR-9s in both groups, severe brainstem seizures occurred after forebrain stimulation. The occurrence of brainstem seizures had a random nature and was not related to the sequence of kindling-dependent forebrain seizure progression. The lack of a difference in the occurrence of brainstem seizures between seizure-experienced and AGS-naive GEPR-9s suggest that genetic predisposition is the major factor in forebrain seizure-induced activation of brainstem seizure circuitry. This brainstem seizure activity appears to model pertinent aspects of secondary generalization observed in human partial seizures.

Differential effects of chloral hydrate and pentobarbital sodium on a cocaine level and its catecholamine response in the medial prefrontal cortex: a comparison with conscious rats

Adult male Sprague-Dawley rats anesthetized with chloral hydrate and pentobarbital sodium were used as two different treatment groups. Conscious rats were used as a control group. By using baseline (precocaine) concentration as 100%, after cocaine administration (3.0 mg/kg i.v.), the maximal dopamine (DA) increase occurring at the first microdialysis collection period (20 min) in the medial prefrontal cortex was 299 +/- 46% for the chloral hydrate group, 168 +/- 12% for the pentobarbital sodium group, and 325 +/- 23% for the conscious group. At the same time, norepinephrine (NA) increases reached a maximum and were 162 +/- 20%, 100 +/- 5%, and 141 +/- 17%, respectively. The maximal changes of DA and NA in the chloral hydrate group and in the control group were both significantly higher than that in the pentobarbital sodium group. Meanwhile, the cocaine concentration was higher over a 100-min period of time in the chloral hydrate group when compared with the pentobarbital group and the control group. The peak cocaine concentration in dialysate occurred in the same time slot of maximal DA and NA responses, which were 0.65 +/- 0.08, 0.30 +/- 0.02, and 0.41 +/- 0.05 microM, respectively. Anesthetics suppress the pharmacologic response of neurons, which may explain the difference in catecholamine response between the pentobarbital sodium and the conscious groups. Conversely, because there was no significant difference in DA and NA response between the chloral hydrate group and the conscious group, it may possible be due to the balancing effect between the higher existing cocaine concentration and the anesthetic suppression on pharmacological response of neurons in the chloral hydrate group. The effect of guide cannula implantation on the cocaine-induced catecholamine response was also evaluated.

Monoamine interactions measured by microdialysis in the ventral tegmental area of rats treated systemically with (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin

The effect of (+/-)-8-hydroxy-2-(di-n-propyl-amino)tetralin (8-OH-DPAT), a selective serotonin 5-HT1A agonist, on levels of extracellular norepinephrine (NE), dopamine (DA), and 5-HT (measured simultaneously) was investigated by microdialysis in the ventral tegmental area (VTA) of freely moving rats, and their behavioral activity was monitored. At 50 micrograms/kg s.c., 8-OH-DPAT reduced 5-HT levels but enhanced NE and DA levels in VTA dialysate. These effects were not altered by pretreatment with systemic idazoxan (5 mg/kg i.p.), a selective alpha 2 antagonist, or local sulpiride (10 microM), a selective D2/D3 antagonist. At 500 micrograms/kg s.c., 8-OH-DPAT further enhanced or more persistently reduced dialysate NE or 5-HT content but had little effect on dialysate DA content. Its DA level-increasing effect could be seen dramatically with local infusion of cocaine (30 microM) and, to a lesser extent, sulpiride (10 microM). Depletion of endogenous 5-HT with p-chlorophenylalanine attenuated both the 5-HT level-reducing and DA level-enhancing effects of 8-OH-DPAT without affecting its maximal NE effect and the locomotor-stimulatory effect. Partial depletion of endogenous NE with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine failed to change the monoamine response but diminished the locomotion induced by 8-OH-DPAT. These results suggested that (a) the low dose of 8-OH-DPAT may act at presynaptic 5-HT1A receptors to modulate 5-HT and DA release, while acting at postsynaptic 5-HT1A receptors to modulate NE release; (b) the high dose of 8-OH-DPAT may activate D2 receptors to offset its DA level-increasing effect; and (c) the locomotor-stimulatory effect of 8-OH-DPAT might be mediated primarily by postsynaptic 5-HT1A receptors and the NE system.

Autoregulation and monoamine interactions in the ventral tegmental area in the absence and presence of cocaine: a microdialysis study in freely moving rats

Extracellular levels of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) were measured simultaneously by microdialysis in the ventral tegmental area (VTA) of conscious rats, and locomotor activity was monitored. Extracellular NE, DA and 5-HT was increased by both local infusion (30 microM) and i.p. injection (20 and 40 mg/kg) of cocaine with 5-HT responding most rapidly. DA was the only amine that showed a significantly higher increase to the systemic cocaine dose of 40 mg/kg than 20 mg/kg, and a higher response to local cocaine (30 microM) than systemic cocaine (20 mg/kg). In the following experiments, the monoamine autoreceptor antagonists idazoxan (alpha-2, 100 microM), sulpiride (D2 DA/D3 DA, 10 microM) and methiothepin (5-HT1/5-HT2, 20 microM) were focally applied into the VTA before cocaine application. Idazoxan or methiothepin increased only local cocaine-induced NE or 5-HT output, whereas sulpiride increased both local and systemic cocaine-induced DA output, consonant with the importance of somatodendritic monoamine autoreceptors in addition to accumbens-VTA feedback pathways. Both idazoxan and methiothepin increased the basal output of all three amines without modifying cocaine (30 microM or 20 mg/kg)-induced output of DA/5-HT or NE/DA, whereas sulpiride promoted cocaine-induced NE output without modifying basal NE/5-HT output and cocaine-induced 5-HT output, implying complex interactions between monoamines. Idazoxan or methiothepin depressed, whereas sulpiride stimulated cocaine (20 mg/kg)-induced motor activity. The analysis of behavioral/neurochemical relationships revealed a negative correlation between dialysate NE output and motor activity in the cocaine alone and idazoxan/cocaine groups, and a positive correlation between dialysate DA output and motor activity in the sulpiride/cocaine and methiothepin/cocaine groups.

Effects of locally applied cocaine, lidocaine, and various uptake blockers on monoamine transmission in the ventral tegmental area of freely moving rats: a microdialysis study on monoamine interrelationships

Microdialysis was used to compare the effect of local perfusion of cocaine with that of functionally similar compounds on extracellular norepinephrine, dopamine, and serotonin (measured simultaneously) in the ventral tegmental area of freely moving rats. Tetrodotoxin (1 microM) potently inhibited both basal and cocaine-induced dialysate monoamine outputs. The local anesthetic lidocaine produced little or no effect on the monoamine output, whereas all uptake blockers tested (at 0.1-1,000 microM) increased the monoamine output in a dose-dependent manner. The selective norepinephrine-uptake blockers desipramine and nisoxetine did not show any selectivity for norepinephrine, whereas the selective serotonin-uptake blockers fluoxetine and citalopram, as well as the selective dopamine-uptake blocker GBR 12935, preferentially (but not exclusively) increased their target amine. Cocaine at low concentrations (1-10 microM) increased the three amines similarly, but at higher concentrations (100-1,000 microM) caused a relatively higher dopamine output. A positive relationship between blocker-induced dialysate norepinephrine and dopamine outputs suggests significant interactions between monoamine systems. The present results indicate that cocaine's action in the ventral tegmental area involves not only a dopamine-, but also a norepinephrine- and a serotonin-related component, and that cocaine-induced monoamine increase is independent of its local anesthetic property.

Facilitation of amygdala kindling development and kindled seizures by metaphit

The effect of metaphit (a phencyclidine analogue with an acylating isothiocyanate) on kindling development and kindled seizures from amygdala was investigated in rats pretreated once with metaphit. Administration of a single dose of metaphit (10 or 20 mg/kg intraperitoneally i.p.) 4 h before the first electrical stimulation of the amygdala did not in itself induce seizures, but greatly facilitated development of behavioral seizures during kindling. This effect persisted throughout the whole process of electrical amygdala kindling without further dosing. In contrast, metaphit only transiently and modestly increased the growth of afterdischarge (AD) duration. In kindled rats, pretreatment with a single dose of metaphit (20 mg/kg) 8 h before the test stimulation reduced the threshold current required to elicit a stage 5 seizure and shortened the latency for bilateral forelimb clonus (BFC) without changing AD duration or BFC duration. The facilitation of kindling development and kindled seizures may be due to an excessive excitatory transmission by metaphit in the limbic seizure circuitry.

GBR 12909 and 12935 block dopamine uptake into brain synaptic vesicles as well as nerve endings

GBR 12909 and 12935, commonly used as potent neuronal dopamine uptake blockers, also inhibit dopamine uptake into brain synaptic vesicles. The concentrations required for the latter activity (34-45 nM) are one order of magnitude higher than those required for inhibiting neuronal uptake of dopamine (1-6 nM). In contrast, the two activities differ by three orders of magnitude for cocaine (137 microM versus 0.35 microM). We propose that the vesicular effect of GBR-type dopamine uptake blockers should be taken into account when interpreting in vivo experiments.

Differential effects of chloral hydrate and pentobarbital sodium on cocaine-induced electroencephalographic desynchronization at the medial prefrontal cortex in rats

We evaluated the effects of two anesthetics on the cocaine-induced electroencephalographic (EEG) desynchronization in male, Sprague-Dawley rats. One group was anesthetized with chloral hydrate (400 mg/kg, i.p., 80 mg/kg/h i.v. supplement; group A). The other group was anesthetized with pentobarbital sodium (50 mg/kg, i.p., 10 mg/kg/h i.v. supplement; group B). The degree of EEG desynchronization after cocaine administration (1.5 mg/kg, i.v.) was expressed as an increase in the mean power frequency (MPF) and a decrease in the root mean square (RMS). These maximal increases and decreases were observed to be larger in group A (MPF: 43.3 +/- 7.0% increase; RMS: 47.4 +/- 5.0% decrease) than in group B (MPF: 17.8 +/- 3.6% increase; RMS: 19.2 +/- 2.5% decrease). Our laboratory previously proved that dopaminergic neurotransmission at the medial prefrontal cortex (mPFC) participated in the cocaine-induced EEG desynchronization and that both D-1 and D-2 receptors were involved in the process. Therefore, in vivo microdialysis coupled with high performance liquid chromatography was used to quantify the changes of extracellular dopamine (DA) concentrations at the mPFC for 90 minutes at 10 minute intervals after 1.5 mg/kg cocaine i.v. injection. The extracellular DA increases in both groups was rapid and reached the maximal peak within 10 min. There was no significant difference in the maximal increase of DA between groups (group A: 375.2 +/- 35.77% versus group B: 332.2 +/- 16.69% over basal value). These results suggest that different anesthetics may differentially affect cocaine-induced EEG desynchronization and this difference has no bearing on the DA response in the mPFC.

Dopamine and serotonin release-regulating autoreceptor sensitivity in A9/A10 cell body and terminal areas after withdrawal of rats from continuous infusion of cocaine

The effects of dopamine (DA) and 5-hydroxytryptamine (5-HT) autoreceptor agents on electrically induced [3H]DA and [3H]5-HT release from superfused slices of striatum, nucleus accumbens and ventral mesencephalon (VM) containing A9 and A10 neurons were investigated in rats made tolerant to the stimulatory effect of cocaine on locomotor behavior by a 14-day continuous infusion of cocaine (29 mg/kg/day) by s.c. implanted osmotic minipumps followed by a 7-day drug-free period. In VM, electrically induced [3H]DA was increased, the ability of pergolide to inhibit this release was abolished, but the ability of sulpiride to facilitate the release was potentiated, implicating a higher concentration of synaptic DA modifying the responsiveness of somatodendritic D2 autoreceptors to D2 agents. Both electrically induced [3H]5-HT release from VM and the stimulatory effect of in vitro cocaine on this release were enhanced whereas the effects of both 5-methoxytryptamine and methiothepin were attenuated, indicating that subsensitivity of 5-HT autoreceptors developed in DA cell body regions. In striatum and nucleus accumbens, no significant changes were observed in [3H]DA and [3H]5-HT release, except for a modest reduction in the effects of both pergolide and sulpiride on electrically induced [3H]DA release from striatum. These results emphasize the importance of pretreatment-induced changes in DA cell body regions, rather than terminal areas, under the present conditions. The observed increase in DA autoinhibitory tone and subsensitivity of 5-HT release-regulating autoreceptors in the VM may contribute to the locomotor tolerance upon cocaine challenge after continuous cocaine.

[3H]dopamine and [3H]serotonin release in vitro induced by electrical stimulation in A9 and A10 dopamine regions of rat brain: characterization and responsiveness to cocaine

The present study investigated [3H]dopamine (DA) and [3H]5-hydroxytryptamine (5-HT) release evoked by electrical stimulation in superfused ventral mesencephalon (VM) slices containing A9 and A10 DA neurons. Electrically induced [3H]DA release from VM was, at least, of two origins: one was from DA somatodendrites, regulated by DA autoreceptors, and increased by DA uptake blockers; another was from 5-HT terminals, modulated by 5-HT autoreceptors, and could be minimized by the copresence of fluoxetine during the labeling of the slices. Release of both origins was Ca(++)-dependent and tetrodotoxin-sensitive. Cocaine (10 and 100 microM) modestly increased electrically induced [3H]DA release from DA somatodendrites and concentration-dependently inhibited that from 5-HT terminals. Electrically induced [3H]5-HT release from VM was exclusively from 5-HT terminals, dependent on Ca++, partly blocked by tetrodotoxin, increased by 5-HT uptake blockers and regulated by 5-HT autoreceptors. The autoregulation of [3H]5-HT release partly counteracted the stimulatory effect of cocaine (10 microM) on [3H]5-HT release. Inhibition of 5-HT uptake by cocaine reduced the effectiveness of 5-methoxytryptamine to suppress electrically induced [3H]5-HT release. No evidence was found to support the notion that postsynaptic 5-HT receptors modulate somatodendritic DA release. 5-HT facilitated spontaneous [3H]DA release from VM via a 5-HT/DA transporter-dependent exchange process and inhibited electrically induced [3H]DA release from 5-HT terminals via a 5-HT autoreceptor-mediated mechanism. The dual effects of cocaine on electrically induced [3H]DA release from VM may be attributed to the complex 5-HT/DA and 5-HT autoreceptor/cocaine interactions as well as the relative densities of 5-HT/DA transporters in this region, indicating a possible involvement of the 5-HT system in cocaine's behavioral effects.

Increased heart microsomal Na(+) K(+)-transporting ATPase activity by tetrandrine in spontaneously hypertensive rats

In spontaneously hypertensive rats (SHR), the heart microsomal Na+, K(+)-ATPase showed a reduced activity with a higher Ca2+ sensitivity and lower responsiveness to K+. After SHR were treated with tetrandrine (Tet, ig 30 mg.kg-1, qd x 30 d) or when the microsomes obtained from SHR hearts were incubated with various concentrations of Tet, the myocardial Na+,K(+)-ATPase showed a higher activity with a decreased Km for K+, or ATP and an increased Vmax for K+. The in vitro stimulatory effect of Tet on the enzyme was dependent on the Na+ concentration in medium and was not abolished by CaCl2 1 mmol.L-1 or ouabain 0.1 mmol.L-1. However, when given in vivo, Tet tended to reduce the tolerance of the enzyme to Ca2+ and failed to change the responsiveness of the enzyme to ouabain. In vitro, Tet had similar but weaker stimulatory effect on the Na+,K(+)-ATPase from Wistar Kyoto rats.

Effect of tetrandrine on myocardial Na+, K(+)-ATPase in renovascular hypertensive rats

In renovascular hypertensive rats (RVHR, two-kidney, one-clip model), the myocardial Na+, K(+)-ATPase showed a reduced activity. Though its sensitivities to K+ and ouabain (Oua) were not changed, the enzyme was less responsive to Na+ and ATP, and also much more susceptible to the inhibitory effect of Ca2+. Tetrandrine (Tet, ig 50 mg.kg-1, qd x 26 d) increased the myocardial Na+, K(+)-ATPase activity in RVHR. However, in vitro, Tet elevated moderately the enzyme activity in RVHR only at high concentrations (100-1,000 mumol.L-1), and failed to influence the enzyme activity in normotensive rats. In RVHR, treatment by Tet in vivo increased the degree of the Na+, K(+)-ATPase activation under suboptimal substrate (Na+, K+, or ATP) concentrations and antagonized the inhibitory effect of Ca2+ or Oua. Similar results were found when the enzyme preparation from RVHR was incubated with Tet 10 mumol.L-1 during ATPase analysis. On the contrary, the myocardial Mg(2+)-ATPase activity was higher in RVHR. Tet depressed this enzyme both in vivo and in vitro. These facts indicate that the increased myocardial Na+, K(+)-ATPase activity in RVHR is not only secondary to the calcium channel blocking or antihypertensive action of Tet but also due to its direct effects on the Na+, K(+)-ATPase and Mg(2+)-ATPase.

[Protecting effects of m-nifedipine on isoproterenol-induced myocardial injury in rats]

To test whether m-nifedipine (m-Nif) protects heart against myocardial injury induced by a single subcutaneous injection of isoproterenol (Iso) 30 mg/kg, male rats were injected subcutaneously twice daily with m-Nif 6 mumols/kg for 4 d. Hemodynamic changes, serum creatine kinase activity and ion contents of myocardial tissue and mitochondria were assessed about 6 h after Iso injection. While it did not notably influence blood pressure, heart rate and left ventricular contracting function of rats, m-Nif markedly attenuated calcium accumulation in myocardial tissue and mitochondria, reduced magnesium and potassium loss in myocardial tissue, depressed the release of creatine kinase and prevented the elevation of left ventricular end diastolic pressure. These beneficial effects of m-Nif were similar to those of nifedipine (Nif). However, m-Nif decreased minute tension-time index more significantly than the same dose of Nif. It is possible that m-Nif protects the rat heart from isoproterenol-induced injury by inhibiting transsarcolemmal calcium influx.